relationships among predators, prey and habitat use … · frequencies for each habitat class....

RELATIONSHIPS AMONG PREDATORS, PREY AND HABITAT USE IN SOUTHERN SASKATCHEWAN,

SPRING & SUMMER 2010

A report prepared by GILBERT PROULX, NEIL MACKENZIE,

BENJAMIN PROULX, and KEITH MACKENZIE

and submitted to Saskatchewan Association of Rural Communities (SARM)

Saskatchewan Ministry of Agriculture & Rural Development - ADF Regina, Saskatchewan

for ACAAF funding

18 January 2011

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Relationships among predators, prey and habitat use in southern Saskatchewan, spring and summer 2010 Alpha Wildlife Research & Management Ltd.

EXECUTIVE SUMMARY

Data on the effects of terrestrial carnivores on Richardson’s ground squirrel populations are necessary for the development of a comprehensive Integrated Pest Management program. The objectives of this study were to:

1. Evaluate multi-scale habitat selection by badgers. 2. Assess the effect of badger, red fox and long-tailed weasel predation on ground squirrel

population densities. 3. Study red fox family movements and activities in ground squirrel fields in the vicinity of

their dens. 4. Study food habits of badger, red fox and long-tailed weasels in landscapes with well-

established Richardson’s ground squirrel populations vs. fields with few ground squirrels. The study of predator-prey relationships was conducted in southwest Saskatchewan.

Landscapes inhabited by 3 badgers were studied from 2008 to 2010. In all cases, the observed distribution of ground squirrel holes per vegetation type differed (P < 0.05) from expected. Ground squirrel holes were significantly (P < 0.05) more frequent in grass and buckbrush in 2008, in fallow and alfalfa in 2009, and in pasture in 2010 (Table 3). Each year, badgers established their hunting grounds in vegetation types with a significantly greater number of ground squirrel holes. This distribution of badger hunting grounds suggests that badgers do not establish their hunting grounds at random; they select landscape areas with the greatest abundance of ground squirrel burrow openings. There was a significant (r = 0.76, P < 0.005) linear relationship (Y = 0.07X + 17.9) between densities of badger and ground squirrel burrow openings. The number of ground squirrels/ha in 20 x 20 m regions overlapping 2 fox dens was significantly (P = 0.04) lower than in adjacent areas. Pups did not hunt in adjacent areas. The impact of long-tailed weasel predation on ground squirrel juvenile populations was assessed in summers of 2008 and 2010. The average capture rate of juveniles in study plots with latrines was significantly different (P < 0.05) from that of study plots (located in the same field) without latrines. On average, in 2008 and 2010, there were 9 ( 4.8) juveniles/ha in 7 study plots with latrines, compared to 28.6 ( 15.1) juveniles/ha in 21 study plots without latrines. Overall, there were 68.5% less juveniles in study plots with latrines than in other study plots. From 2008 to 2010, badger food habits consisted mostly of Richardson’s ground squirrels from April to July. Foxes inhabiting ground squirrel-rich areas fed mainly on ground squirrels. In ground squirrel-poor areas, they fed mostly on deer mice. The proportions of June-July weasel scats with Richardson’s ground squirrel remains, and mean volumes, were similar from year to year. Ground squirrel remains corresponded to approximately 63% of all prey items in 2009, and >79 % in 2008 and 2010. For all predators studied, when ground squirrels were the main food item, the prey diversity index was low, this suggesting that badgers, foxes and weasels specialized on this prey. When ground squirrels were scarce or difficult to acquire (e.g., during hibernation), they fed on small mammals, birds and insects without any particular preference.

This study showed that predators may impact individually or as a group on ground squirrels, and may play an important role in minimizing the risk of rodent population outbreaks. Integrating predator conservation in Richardson’s ground squirrel population management will require site-specific approaches. Further investigations are needed to better determine when and how to control ground squirrels without endangering the survival of predators.

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Table of Contents

1.0 INTRODUCTION .............................................................................................................. 5

2.0 OBJECTIVES ..................................................................................................................... 5

3.0 STUDY AREA & METHODS ........................................................................................... 5

3.1 Multi-scale Habitat Selection by Badgers ........................................................................ 6

3.2 Assessment of the effects of badger, red fox and long-tailed weasel predation on ground squirrel population densities........................................................................................................ 7

3.3 Study of red fox family movements and activities in ground squirrel fields in the vicinity of their dens .................................................................................................................... 9

3.4 Study of badger, red fox and long-tailed weasels food habits ......................................... 9

4.0 RESULTS ........................................................................................................................... 9

4.1 Multi-scale Habitat Selection by Badgers ........................................................................ 9

4.1.1 2010 Male Badger # 702 ........................................................................................... 9

4.1.2 2010 Untagged Female badger ............................................................................... 10

4.1.3 Synthesis of 2008-2010 data ................................................................................... 12

4.2 Assessment of the effects of red fox and long-tailed weasel predation on ground squirrel population densities ................................................................................................................... 14

4.2.1 Red fox .................................................................................................................... 14

4.2.2 Long-tailed weasel .................................................................................................. 15

4.3 Study of red fox pup movements and hunting activities at den sites ............................. 16

4.4 Study of badger, red fox and long-tailed weasels food habits ....................................... 18

4.4.1 Badger ..................................................................................................................... 18

4.4.2 Red fox .................................................................................................................... 21

4.4.3 Long-tailed weasel .................................................................................................. 27

4.0 DISCUSSION ................................................................................................................... 27

5.0 MANAGEMENT CONSIDERATIONS .......................................................................... 28

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6.0 ACKNOWLEDGMENTS ................................................................................................ 30

7.0 LITERATURE CITED ..................................................................................................... 30

APPENDIX I ................................................................................................................................ 32

APPENDIX II - RELATIONSHIPS AMONG PREDATORS, PREY AND HABITAT USE IN SOUTHERN SASKATCHEWAN, 2008 ..................................................................................... 33

1.0 INTRODUCTION ............................................................................................................ 36

2.0 STUDY AREA ................................................................................................................. 37

3.0 METHODS ....................................................................................................................... 38

4.0 RESULTS ......................................................................................................................... 40

5.0 DISCUSSION ................................................................................................................... 55

6.0 RECOMMENDATIONS .................................................................................................. 58

7.0 ACKNOWLEDGMENTS ................................................................................................ 58

8.0 LITERATURE CITED ..................................................................................................... 58

APPENDIX III - THE RICHARDSON’S GROUND SQUIRREL (SPERMOPHILUS RICHARDSONII) RESEARCH & CONTROL PROGRAM 2009-2010 ..................................... 64

1.0 INTRODUCTION ............................................................................................................ 67

2.0 STUDY AREA ................................................................................................................. 67

3.0 TOXICANTS .................................................................................................................... 68

4.0 GROUND SQUIRREL -VEGETATION HEIGHT RELATIONSHIP ........................... 98

5.0 ASSESSMENT & DEVELOPMENT OF CAPTURE-EFFICIENT TRAPPING DEVICES .................................................................................................................................... 101

6.0 PREDATION .................................................................................................................. 106

7.0 DISCUSSION ................................................................................................................. 134

8.0 ACKNOWLEDGEMENTS ............................................................................................ 139

9.0 LITERATURE CITED ................................................................................................... 139

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1.0 INTRODUCTION

An effective Integrated Pest Management (IPM) to effectively control Richardson’s ground squirrel1 includes predation as a control method. A better understanding of predator-prey relationships in agricultural ecosystems could provide producers with an inexpensive and long-term solution to Richardson’s ground squirrel population outbreaks. In spring and summer 2008 (Proulx et al. 2009) and 2009 (Proulx et al. 2010), Alpha Wildlife Research & Management successfully demonstrated that terrestrial predators were effective predators of ground squirrels. Scat analyses showed that badgers, long-tailed weasels, and canids fed significantly more often on Richardson’s ground squirrels than on any other prey from May to July. Badgers appeared to select their home range at both landscape (selecting fields with the most abundant ground squirrel populations) and stand (selecting areas with higher population levels and easier digging sites) levels. In June 2008, in fields with weasel latrines (indicative of high activity levels), ground squirrel juvenile populations were, on average, 44% less abundant than in fields without weasel latrines (Proulx et al. 2009). Scat analyses suggested that ground squirrels may represent more than 60% of prey eaten by coyote and red fox families.

Data on the effects of terrestrial carnivores on ground squirrel populations are still scant. More information is required on the habitat and ground squirrel population characteristics of these carnivores’ hunting grounds. Habitat selection at landscape and stand levels need to be further documented2. Little data exist on the percentage of ground squirrel populations controlled through predation. Such information is vital for the development of a comprehensive IPM program for Richardson’s ground squirrels. 2.0 OBJECTIVES The objectives of this study were to:

1. Evaluate multi-scale habitat selection by badgers. 2. Assess the effect of badger, red fox and long-tailed weasel predation on ground squirrel

population densities. 3. Study red fox family movements and activities in ground squirrel fields in the vicinity of

their dens. 4. Study food habits of badger, red fox and long-tailed weasels in landscapes with well-

established Richardson’s ground squirrel populations vs. fields with few ground squirrels. 3.0 STUDY AREA & METHODS

The study of predator-prey relationships was conducted in southwest Saskatchewan (Figure 1).

1 See Appendix I for a list of scientific names. 2 In 2009, such data were gathered for one radio-collared adult female, and another adult living nearby. However, with the latter, data were scarce and did not lead to statistical analyses.

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Figure 1. Location of the study area.

3.1 Multi-scale Habitat Selection by Badgers In spring 2010, badger movements were recorded over at least a week using transmitter

fixes and/or night spotting to determine hunting grounds, and the general use of habitats by the animals. Transects crossing annual crops, pastures and grasslands were laid out 200-400 m apart, across landscapes where badger activities were recorded to determine the abundance and distribution of Richardson’s ground squirrel and badger holes (within 30 cm from the transect line) in each habitat type. The proportion of inventory transects within each habitat type was used to determine the expected frequency of ground squirrel and badger holes per habitat type. Chi-square statistics (Zar 1999) were used to compare observed to expected frequencies of hole intersects per habitat type (Proulx 2006, 2009). If chi-square analyses suggested overall significant differences between the distributions of observed and expected frequencies, a G test for correlated proportions (Sokal and Rohlf 1981) was used to compare observed to expected frequencies for each habitat class. Probability values ≤ 0.05 were considered statistically significant.

On the basis of observations of badger movements and activities, hunting grounds were delineated. The average number of Richardson’s ground squirrel and badger holes within hunting grounds were counted and compared to that of control plots of similar size located at random, 30 m on each side of the hunting ground, unless they overlapped with another hunting ground

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(Proulx et al. 2008). Comparisons between the average numbers of Richardson’s ground squirrel and badger holes in badger hunting grounds and control areas were carried out with the Student’s t (Zar 1999) and Mann-Whitney U (Siegel 1956) tests. A simple linear regression model was used to determine the relationship between the density of ground squirrel and badger holes.

3.2 Assessment of the effects of badger, red fox and long-tailed weasel predation on ground squirrel population densities

In order to assess the effect of red fox families on Richardson’s ground squirrel population densities, we studied two dens in late June-early July: one den occupied since spring, and one den recently occupied in late June by a fox family. We established a 2.25 ha study plot with the den at its centre. We inventoried burrow openings, and live-trapped (200 15 x 15 x 48 cm; Tomahawk live traps, Tomahawk, Wisconsin) and ear-tagged ground squirrels on June 30 and re-captured them on July 8. Burrow openings and capture sites were carefully located on a map including 4 regions (Figure 2); the boundaries of the first region took into consideration the extent of pup activities around the den entrance as determined with a remote camera (Figure 3) and distribution of feces. We tested our hypothesis that the population of ground squirrels in the first region would be lower than in other regions using Mann-Whitney U test (Siegel 1956) and a 0.05 level of significance.

We also established 0.25 ha study plots over a hunting ground frequently visited by a fox family inhabiting a nearby den, and a control area located 30 m away. On July 8, we inventoried the number of burrow openings and ground squirrels in both study plots. We recaptured ground squirrels on July 15.

In previous years, we noticed that live-trapping ground squirrels disturbed badgers, which then left the study area to come back only later. For this reason, we did not attempt to assess the impact of 3 badgers (Section 3.1) on ground squirrel populations inhabiting their hunting grounds. The impact of badgers on ground squirrel populations was surmised on the basis of scat analyses (Section 3.4).

The impact of long-tailed weasel predation on ground squirrel juvenile populations was assessed in summer. Within a same quarter section, live-trapping capture success was used to evaluate juvenile ground squirrel populations in 0.5 ha study plots (12 traps/plot checked twice a day) from 6 to 8 June, and in 4.0 ha study plots (60 traps/plot checked twice a day) from 14 to 16 June, for toxicant studies (see Proulx 2011). All the study plots had similar vegetation. In 3 study plots that were located beside each other in one section of the field, visual observations and the presence of latrines with large accumulations of scats deposited in the space of about 0.1m2 confirmed residency by weasels (Proulx et al. 2009). The average capture rate of juveniles in study plots with latrines was compared to that of study plots (located in the same field) without latrines using Mann-Whitney U test and a 0.05 level of significance. Data were also pooled with Proulx et al.’s (2009) data, and analyzed with a Student-t test (Zar 1999).

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Figure 2. Sub-divisions of a 2.25 ha study plot laid over a fox den.

Figure 3. Example of a fox den monitored with a remote camera set amng pails.

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3.3 Study of red fox family movements and activities in ground squirrel fields in the vicinity of their dens

In order to better understand the fox-Richardson’s ground squirrel relationship, remote control cameras were set at dens3. Digital camera pictures were used to better understand the hunting activities of red fox pups. Fox families were also watched at distance to determine if pups spent time hunting ground squirrels.

3.4 Study of badger, red fox and long-tailed weasels food habits As in 2008 and 2009, scats collected during toxicant studies (Proulx 2011) and predation

work were collected and analyzed in Alpha Wildlife’s laboratory. Data were compared to those of previous years using chi-square statistics for frequencies of occurrence of diverse food items, and Anova test for volumes (Proulx et al. 2010). A simple linear regression model was used to determine the relationship between prey diversity index and the frequency of ground squirrel remains in scats. 4.0 RESULTS 4.1 Multi-scale Habitat Selection by Badgers 4.1.1 2010 Male Badger # 702

We observed a male badger hunting activities starting in mid-April with spot lighting. On May 17, we captured it to implant a transmitter (frequency 702). Four types of vegetation cover were found within the landscape inhabited by the badger: wheat, pasture dominated by crested wheat, meadow, and seeded grassland. A total of 163 Richardson’s ground squirrel holes were recorded along 4 transects that were 290-404 m apart and 1161-1232 m long (Table 1). The observed distribution of ground squirrel holes per vegetation type differed (2 = 67.6, df: 3, P < 0.001) from expected. Ground squirrel holes were significantly less frequent than expected in wheat (G= 23.8, df: 1, P < 0.001), but significantly more frequent in pasture (G= 13, df:1, P < 0.001).

Table 1. Distribution of Richardson’s ground squirrel burrow holes across the landscape inhabited by badger # 702, spring 2010.

Vegetation type Length – m (%) Number of Richardson’s ground squirrel burrow holes/%

Wheat 2096 (43.9) 25 (15.3) Pasture 1922 (40.3) 114 (69.9) Meadow 206 (4.3) 4 (2.5) Seeded grassland 549 (11.5) 20 (12.3) Total 4773 (100) 163 (100)

3 A radio-telemetry study was planned to investigate this aspect of the research program. However, while a net gun was purchased to capture red foxes, it proved to be ineffective due to high vegetation. Furthermore, some of the foxes that had been identified for radio-telemetry work disappeared early in the summer. The radio-telemetry study was therefore cancelled, and more time was spent on studying foxes at their dens.

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Male badger no. 702 made a greater use of the pasture where it established 4 hunting grounds (Table 2) averaging 0.37 ( SD = 0.3) ha. The average number of ground squirrel holes/ha in hunting grounds (n = 4, x = 824.3 211.6) was significantly greater (t = 6.1, P < 0.005) than that of controls (n = 8, x = 158.4 81.3). The average number of badger holes/ha in hunting grounds (n = 4, x = 76.2 47.1) was also significantly greater (U test, P < 0.002) than that of controls (n = 8, x = 4 4.6).

A significant relationship existed between the density of badger holes/ha and the density of Richardson’s ground squirrel holes/ha. The linear regression between densities was Y = 4.6 X + 283 (r = 0.65, P < 0.05) (Figure 4).

4.1.2 2010 Untagged Female badger In 2009, 2 hunting grounds of an “unknown” badger were found and studied by Proulx et

al. (2009). The badger was still active in fall 2009 but its hunting grounds could not be further investigated due to snow cover. In spring 2010, we observed this badger with 2 pups. Early in spring, we found a 3rd hunting ground (0.5 ha) where the badger had been active in fall 2009. There were 144 ground squirrel and 29 badger holes in the hunting ground, compared to 28 ground squirrel and 1 badger hole in 1 control (0.49 ha).

Figure 4. Relationship between the densities of badger no. 702 and Richardson’s ground squirrel holes/ha, spring 2010.

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Table 2. Densities of ground squirrel and badger holes in hunting grounds and respective control areas of male adult badger no. 702, spring 2010.

Hunting Grounds Control plots

No. (ha) Richardson’s ground squirrel holes

Badger holes No. (ha) Richardson’s ground squirrel holes

Badger holes

Abundance Density/ha Abundance Density/ha Abundance Density/ha Abundance Density/ha

1 (0.22) 243 1104.5 11 50.0 1a (0.35) in wheat 66 188.6 0 0

1b (0.32) in pasture 23 71.9 4 12.5

2 (0.34) 243 714.7 15 44.1 2a (0.32) in wheat 35 109.4 1 2.9

2b (0.32) in pasture 59 184.4 0 0

3 (0.80) 688 860 52 65 3a (0.62) in pasture 84 135.5 4 6.5

3b (0.5) in alfalfa seeded field

72 100 1 2.0

4 (0.11) 68 618.1 16 145.5 4a (0.13) in pasture 46 353.5 1 7.7

4b (0.13) in pasture 13 100 0 0

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4.1.3 Synthesis of 2008-2010 data Landscapes inhabited by 3 badgers were studied from 2008 to 2010. In all cases, the observed distribution of ground squirrel holes per vegetation type differed (P < 0.05) from expected. Ground squirrel holes were significantly (P < 0.05) more frequent in grass and buckbrush in 2008, in fallow and alfalfa in 2009, and in pasture in 2010 (Table 3). Each year, badgers established their hunting grounds in vegetation types with a significantly greater number of ground squirrel holes. In 2008, even though ground squirrel holes were significantly more abundant in bulrush and grass, badger hunting grounds were all in grass where digging was easier. In 2009, although ground squirrel holes were abundant in pasture, their concentrations were significantly greater in fallow and alfalfa. While badger scats were found in pasture, all hunting grounds were found in fallow and alfalfa. This distribution of badger hunting grounds suggests that badgers do not establish their hunting grounds at random; they select landscape areas with the greatest abundance of ground squirrel burrow openings. Table 3. Distribution of Richardson’s ground squirrel burrow holes across landscapes inhabited by badgers, spring 2008 to spring 2010.

Vegetation type Length – m (%) Number of Richardson’s ground squirrel burrow holes

(%)

Distribution of badger hunting grounds

Female no. 207 (2008) Wheat 5035 (84.6) 101 (63.9) 0 Grass 547 (9.2) 32 (20.2)* 3 + 1 overlapping pasture

and wheat Buckbrush 370 (6.2) 25 (15.8)* 0

Total 5952 (100) 158 (100) 4 Untagged Female adult (2009)

Fallow 768 (11.9) 65 (22.6)* 3 Alfalfa 360 (5.6) 38 (13.2)* Wheat 2128 ( 32.9) 50 (17.4) 0 Pasture 3216 (49.7) 135 (46.9) 0 Total 6472 (100) 288 (100) 3

Male no. 702 (2010) Wheat 2096 (43.9) 25 (15.3) 0 Pasture 1922 (40.3) 114 (69.9)* 4

Meadow 206 (4.3) 4 (2.5) 0 Seeded grassland 549 (11.5) 20 (12.3) 0

Total 4773 (100) 163 (100) 4 *Significantly (P < 0.05) greater number of ground squirrel holes.

On average, the Richardson’s ground squirrel and badger hole densities/ha were significantly greater (t 3.7, P < 0.005) in hunting grounds than in control areas (Table 4). This suggests that, within selected landscape portions, badgers established their hunting grounds in areas that were relatively richer in ground squirrel burrow openings. Also, there was a significant (r = 0.76, P < 0.005) linear relationship (Y = 0.07X + 17.9) between densities (Figure 5).

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Table4. Densities of ground squirrel and badger holes in hunting grounds and respective control areas of badgers, 2008-2010.

Hunting Grounds Control plots

No. (ha) Richardson’s ground squirrel holes

Badger holes No. (ha) Richardson’s ground squirrel holes

Badger holes

Abundance Density/ha Abundance Density/ha Abundance Density/ha Abundance Density/ha

Female no. 207 1 (0.38) 404 1063.2 27 71.1 1a (0.42) 70 166.7 8 19.0

1b (0.42) 15 35.7 4 9.5 2 (0.23) 463 2013.0 43 187.0 2a (0.42) 73 173.8 12 28.6

2b (0.42) 114 271.4 11 26.2 3 (0.22) 133 604.5 7 31.8 1 (0.42) 94 223.8 3 7.1 4 (0.10) 155 1550.0 13 130.0 1a (0.42) 212 504.8 17 40.5

Male badger no. 702 1 (0.22)

243

1104.5

11

50.0

1a (0.35) 66 188.6 0 0 1b (0.32) 23 71.9 4 12.5

2 (0.34)

243

714.7

15

44.1

2a (0.32) 35 109.4 1 2.9 2b (0.32) 59 184.4 0 0

3 (0.80)

688 860.0 52 65.0 3a (0.62) 84 135.5 4 6.5 3b (0.5) 72 100.0 1 2.0

4 (0.11) 68 618.1 16 145.5 4a (0.13) 46 353.5 1 7.7 4b (0.13) 13 100.0 0 0

Untagged female 1 (0.49) 54 110.0 14 28.6 1a (0.49) 14 28.6 0 0

1b (0.49) 26 53.1 0 0 2 (0.49) 42 85.7 9 18.4 2a (0.49) 21 42.9 4 8.2

2b (0.49) 8 16.3 0 0 3 (0.50) 144 288.0 29 58.0 1 (0.50) 28 56.0 1 2.0

x

(SD)

819.2

(593.5)

75.4

(54.5)

148.2

(124.6)

9.1

(11.6)

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Figure 5. Relationship between the densities of badger and Richardson’s ground squirrel holes/ha, 2008-2010.

In 2009, the den of female no. 207 was located within a 3-m-wide grassland strip that crossed a wheat field. Badger activities at the den could not be confirmed due to the animal’s shyness (it would seek refuge as soon as it heard a vehicle or saw human activity) and the height of the surrounding crop. There were 54 ground squirrel and 4 badger holes in a 3 m-wide x 400-m-long grassland strip encompassing the den. In one 3 m x 400 m control strip, only 10 ground squirrel holes were recorded. In the other control strip, 6 ground squirrel and 1 badger holes were found. Richardson’s ground squirrel and badger activity appeared to be greater in the grassland strip than in the wheat field.

From 2008 to 2010, badgers established their hunting grounds according to the distribution of Richardson’s ground squirrels at landscape and stand levels, this suggesting a multi-scale selection process.

4.2 Assessment of the effects of red fox and long-tailed weasel predation on ground squirrel population densities 4.2.1 Red fox At the den occupied by a family since spring, the number of Richardson’s ground squirrel holes at the den (Region 1) was lower than that observed in all other regions (Table 5). At the den dug out by a fox family in late June, the number of ground squirrel holes surrounding the den was higher than in other regions (Table 5). However, the number of ground squirrels/ha in Region 1 of both study plots was significantly (P = 0.04) lower than that of all other regions. The

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effect of the red fox family was therefore apparent in Region 1. The number of ground squirrels/ha in other regions varied considerably, and there was no apparent distribution trend (Table 5). In both study plots, approximately 75% of the tagged animals were recaptured on July 8. Causes of death were unknown. On July 8, the number of burrow entrances and ground squirrels was greater in the 0.25 ha study plot laid over a hunting ground than in the control area. On July 15, only 50% of the animals were recaptured in both populations. The effect of red foxes on ground squirrels inhabiting the hunting ground was not apparent. Table 5. Number of burrow openings and ground squirrels in 2 study plots centered on a den, and in a hunting ground and control area, summer 2010. Number of

Fox family established since spring Fox family established in late June Hunting ground (0.25 ha)

Control area (0.25 ha)

Region 1

(0.04 ha)

Region 2

(0.21 ha)

Region 3

(0.75 ha)

Region 4

(1.25 ha)

Region 1

(0.04 ha)

Region 2

(0.21 ha)

Region 3

(0.75 ha)

Region 4

(1.25 ha)

Burrow openings/ha

75 152 512 106 400 310 245 227 119 60

Ground squirrels/ha

0 76 26 48 0 9.5 16 26 20 8

4.2.2 Long-tailed weasel 2010 study plots with latrines: In June 2010, we found that the number of juvenile ground squirrels captured from 6 to 8 June in 2 study plots with weasel latrines was 2 and 5, respectively, and averaged 3.5. In another section of the field, in 6 study plots without latrines, the number of captures ranged from 17 to 38, and averaged 23.7. The number of captures in study plots with latrines was significantly lower than that of other study plots (U test, P = 0.04). On average, the number of captures in study plots with latrines was 85% less than in study plots without latrines. In one 4-ha study plot with latrines, 9 juveniles were captured from 14 to 16 June. In two other plots without latrines, 88 and 84 juveniles were captured, i.e, almost 10 times more animals.

Overall, there were 5.4 juveniles/ha in study plots with latrines compared to 41.1 juveniles/ha in study plots without latrines. The difference between means was significantly different (t = 3.367, P < 0.05). Control of juvenile ground squirrels by weasels corresponded to 86.9% of the population. An analysis of scats collected at latrines showed that ground squirrels were the main prey in frequency and in volume (Table 6).

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Table 6. Frequencies and mean volumes (%) of food items in long-tailed weasel scats from 3 study plots with latrines, June 2010.

Food item

Study Plots BS No. 6

n = 82 BS No. 7

n = 35 PT No. 3

n = 11 Frequency (%

of prey items)*

Mean volume - % (SD)

Frequency (% of prey

items) *

Mean volume -

% (SD)

Frequency (% of prey items)*

Mean volume -

% (SD)

Richardson’s ground squirrel

76 (90.5) 92.5 (26.2) 23 (65.7) 65.7 (48.2) 11 (91.7) 98.6 (4.5)

Deer mouse 5 (6.0) 6.1 (24.1) 7 (20.0) 20 (40.6) - -

Western harvest mouse

- - 2 (5.7) 5.7 (23.6) - -

Vegetation 2 (2.4) 1.3 (11.1) 3 (8.6) 8.6 (48.2) 1 (8.3) 1.4 (4.5)

Other 1 (1.2) 0.1 (0.8) - - - -

Synthesis of 2008 & 2010 data: In 2008, 4 study plots with latrines had an average of 7 ( 2.2) juveniles compared to 12.5 ( 3.3) juveniles in study plots without latrines (Proulx et al. 2009). The difference between study plots was significant (t = 3.11, P < 0.005). There were 44% less juveniles in study plots with weasel latrines. On average, in 2008 and 2010, there were 9 ( 4.8) juveniles/ha in 7 study plots with latrines, compared to 28.6 ( 15.1) juveniles/ha in 21 study plots without latrines. There was a significant difference (t = 5.211, P < 0.005). Overall, there were 68.5% less juveniles in study plots with latrines than in other study plots. 4.3 Study of red fox pup movements and hunting activities at den sites Remote cameras were placed at 3 dens from May 14 to June 2, when pups were likely 4-6 weeks old (Table 7, Figure 6). Monitoring pups’ exits was difficult. John den was located under grain bins and had many exits that could not be monitored all at the same time. The females of Thibault and Bickner families kept moving their pups when they noticed the presence of cameras. Nevertheless, we monitored these 3 families over 217.5 hours (Table 7). John family was active mostly during night, while the two other families were observed during daylight only. Overall, fox pups seem to be active at all times of day. When monitoring badger no. 2 at night (Section 4.1.1), we observed John family by their den during the day, and Thibault family at night. While remote cameras indicated that fox pups were out during the day when ground squirrels were active, they were not observed with ground squirrel carcasses. Pictures suggested that pups spent most of their time resting, playing, and observing their surroundings.

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Table 7. Exits of fox pups determined with remote cameras set at dens in spring 2010. Family Time period Number of pup exits

Day Night John (3 pups) 14-16 May (50 h 15 min) 2 5

20-27 May (91 h) 0 6

Thibault (5 pups) 31 May – 2 June (47 h) 6 0

Bickner (7 pups) 31 May – 1 June (29 h 15 min)

3 0

Total 217.5 h 11 11

Figure 6. Remote camera frames of red fox families: a and b) John; c) Thibault; and d) Bickner.

18


We watched 5 families at distance from 14 to 25 June, when pups were approximately 8 weeks old. In most cases, foxes spent their time near the den’s entrance resting and observing their surroundings. We observed pups killing ground squirrels in two instances only (Table 8). Pups were not impacting seriously on ground squirrels. However, when visiting dens, we noticed that the vixen cached ground squirrels near dens or dropped carcasses at the entrance of dens (Table 9). Also, fox parents were observed > 100 m from their den when they were hunting or running with ground squirrels in their mouth. Table 8. Observations of pups’ predation on ground squirrels, June 2010.

Family Day Duration Activity outside den No activity outside den Duration Ground squirrel killing

House den (4 pups)

14 June 6 h 25 min 3 h 40 min No 2 h 45 min 15 June 10 h 16

min 10 h 16

min Yes – pups killed 2 ground squirrels -

16 June 9 h 55 min 3 h 25 min No 6 h 30 min John (3 pups) 15 June 1 h 40 min 1 h 18 min No 22 min Loverin (4 pups)

23 June 1 h 53 min 1 h 07 min No 46 min 24 June 7 h 37 mini 6 h 4 min No 1 h 33 min

Gross (3 pups) 23 June 5 h 40 min - No 5 h 40 min Thibault (5 pups)

25 June 5 h 36 min 5 h 36 min No -

Total 41 h 46 min

24 h 22 min

2 observations 17 h 24 min

Table 9. Red fox caches found near dens in May 2010.

Family Cache contents Loverin 4 Richardson’s ground squirrels, 1 least weasel, 1 deer mouse John 1st cache – 14 Richardson’s ground squirrels, 1 deer mouse

2nd cache – 2 Richardson’s ground squirrels Bickner 8 Richardson’s ground squirrels, 7 mice, 1 sparrow Robertson 1 Richardson’s ground squirrel Thibault 1 Richardson’s ground squirrel 4.4 Study of badger, red fox and long-tailed weasels food habits

4.4.1 Badger 2010 scat analysis – There was a significant difference (P = 0.05) in the frequency of scats with Richardson’s ground squirrel remains between April-May and June-July (Table 10). In June-July, when Richardson’s ground squirrel juveniles were numerous, all scats had ground squirrels remains.

There was a significant difference (t = 3.105, P < 0.005) in the mean volume of ground squirrel remains in April-May ( = 56.3 ± 51.2%) and June-July ( = 96.8 ± 7.1%). The prey diversity index was greater in April-May (2.014) than in June-July (0.922). In April-May, badgers fed on small mammals and galliformes (pheasants, partridges), and scavenged on cattle. In June-July, insect and galliforme remains were found in 1 scat only.

19


Table 10. Frequencies and relative volumes (%) of food items in badger scats, spring-summer 2010.

Food item April-May n = 16

June-July n = 8

Frequency (% of prey items)*

Mean volume- % (SD) Frequency (% of prey items)*

Mean volume -% (SD)

MAMMALIA Richardson’s ground squirrel

9 (52.9) 56.3 (51.2) 8 (80.0) 96.8 (7.1)

Deer mouse 2 (11.8) 10 (28.3) - - West harvest mouse

3 (17.6) 18.8 (40.3) - -

Snowshoe hare

1 (5.9) 6.2 (25.0) - -

Cattle 1 (5.9) 6.2 (25.0) - - AVES

Gray partridge

1 (5.9) 2.5 (10.0) 1 (10) 2.5 (7.1)

ARTHROPODA Insect - - 1 (10) 0.8 (2.1) Prey diversity index

2.014 0.922

* Some scats contained more than one food item. Synthesis of 2008-2010 data – In 2008, there was a significant difference (χ2 = 16, df: 3, P < 0.01) in the proportion of scats with of Richardson’s ground squirrel remains from one period to the other (Table 11). From April to July, scats had mammal remains that consisted only of Richardson’s ground squirrels. In August-September, Richardson’s ground squirrel remains were less frequent (Fisher, P = 0.0002). From August to November, the food habits of the badgers became more diversified, including several small mammals, insects and vegetation (possibly ingested when foraging for insects).

From 2008 to 2010, frequencies of scats with Richardson’s ground squirrel remains were similar (P > 0.05) in April-May and in June-July. Mean volumes were also similar (F2,30 = 1.687, P > 0.05) among years. There was a strong relationship (Y = - 0.026 X + 2.898, r = - 0.91, P < 0.05) between the frequency of Richardson’s ground squirrels remains and the prey diversity index (Table 11). When ground squirrels were the main food item, the prey diversity index was low, this suggesting that badgers were specializing on this prey. On the other hand, when ground squirrels were scarce or difficult to acquire (e.g., during hibernation), badgers fed on small mammals, birds and insects without any particular preference.

20


Table 11. Frequencies and mean volumes (%) of food items in badger scats, spring-summer 2008-2010, southern Saskatchewan.

* Some scats contained more than one food item. ** Badger was not considered a prey item.

Food item 2008 2009 2010 April-May*

n = 13 June-July*

n = 7 August-September*

n = 9 October-November*

n = 12 April-May*

n = 4 June-July*

n = 5 April-May*

n = 16 June-July*

n = 8

Freq.(% of prey items)

Mean vol. - %

(SD)


Mean vol. -

% (SD)


Mean vol. -

% (SD)


Mean vol. -

% (SD)


Mean vol. -

% (SD)


Mean vol. -

% (SD)


Mean vol. -

% (SD)


Mean vol. -

% (SD)

MAMMALS Richardson’s ground squirrel

11 (84.6) 84.6 (37.6)

6 (85.7) 85.7 (37.8)

4 (36.4) 50 (53.5)

3 (23.1) 16.9 (37.3)

3 (60) 50 (45.6)

4 (80) 80 (44.7)

9 (52.9) 56.3 (51.2)

8 (80) 96.8 (7.1)

Sagebrush vole - - - - - - 2 (11.1) 4.6 (13.9)

- - - - - - - -

Deer mouse - - - - - - 1 (5.6) 7.5 (27.2)

2 (40) 43.7 (-)

1 (20) 20 (-)

2 (11.8) 10 (28.3)

- -


- - - - - - 1 (5.6) 6.2 (22.2)

- - - - 3 (17.6) 18.8 (40.3)

- -

Snowshoe hare 1 (5.9) 6.2 (25.0)

- -

Cattle 1 (5.9) 6.2 (25.0)

- -

White-tailed deer

- - - - - - 1 (5.6) 7.7 (27.7)

- - - - - - - -

Badger** 1 (-) 1.5 1 (-) 1.6 1 (-) 0.1 4 (-) 11.2 1 (-) 6.3 - - - - - - BIRDS

Galliformes and passeriformes

1 (7.7) 7.7 (27.7)

- - - - - - - - - - 1 (5.9) 2.5 (10.0)

1 (10) 2.5 (7.1)

ARTHROPODS Insect 1 (7.7) 6.2

(22.2) - - 4 (36.4) 47.3

(50.7) 8 (44.4) 45.2

(45.2) - - - - - - 1 (10) 0.8

(2.1) VEGETATION

Grass-type - - 1 (14.3) 12.7 (33.6)

3 (27.3) 2.5 (3.8)

1 (5.6) 0.2 (0.6)

- - - - - - - -

OTHERS Unknown/ Pebbles

- - - - - - 1 (5.6) 0.5 (1.4)

- - - - - - - -

Prey Diversity Index

0.774 0.591 1.573 2.468 0.971 0.722 2.014 0.922

21


4.4.2 Red fox 2010 scat analysis – Red fox families were grouped into 2 groups: 1) landscapes poor in Richardson’s ground squirrels (e.g., annual crops, gravel pit); and 2) landscapes rich in ground squirrels (pastures and grasslands). In 7 out of 10 scat samples collected in ground squirrel-poor landscapes, the main prey was deer mouse (Table 12). In 9 out of 10 scat samples collected in ground squirrel-rich areas, ground squirrels were the main prey (Table 13). There was a significant difference (P < 0.05) in the frequency of scats with Richardson’s ground squirrel remains from ground squirrel- rich and poor areas (Figure 7). Group I consisted mostly of samples collected in ground squirrel-rich areas in June. Gross and Woodrow fox scats were poor in ground squirrel remains in May, but they were relatively rich in June, this suggesting that foxes fed on ground squirrels from nearby grasslands. Groups III to V consisted of samples with relatively few scats with ground squirrel remains. Group II was intermediary; between 46.7 % and 78.6% of scats contained ground squirrel remains. The mean volume of Richardson’s ground squirrel remains was 65.8 ( 16.6) % in ground squirrel-rich areas, and 32.1 ( 18.6) in poor areas. There was a significant difference between these values (t = 4.278, P < 0.05). Foxes inhabiting ground squirrel-rich areas fed mainly on ground squirrels. On average, remains of west harvest mouse were more important in ground squirrel-rich areas ( = 12.2 ± 8.6%) than in poor areas ( = 4.5 ± 3.9 %). The mean volume of deer mouse remains was lower (t = 4.885, P < 0.005) in rich ( = 14.1 ± 14.9%) than in poor ( = 53.5 ± 20.7%) areas. Synthesis of 2008-2010 data – Most scats collected in 2008 and 2009 were from June. Therefore, they were compared to those of June 2010 which included scat samples from ground squirrel-rich areas, and June Gross sample which had a frequency of ground squirrel remains > 60% and was collected nearby squirrel-rich areas (Tables 14 and 15). The frequency of scats with ground squirrel remains was the same (P > 0.05) in most samples. There was, however, a greater number of scats with ground squirrel remains were more frequent in the Kincaid 2008 than in Kincaid 2009 and Aneroid 2009 samples. There was no significant difference (F13, 509, P > 0.05) between mean volumes of the different samples. There was a linear relationship (Y = 0.012 X + 2.349; r = - 0.564) between prey diversity index and the frequency of Richardson’s ground squirrel remains in scats (Tables 14 and 15), i.e., when ground squirrels were important food items, the prey diversity index was low.

22


Table 12. Frequencies and mean volumes (%) of food items in scats of red foxes inhabiting Richardson’s ground squirrel-poor landscapes, May-July 2010, southern Saskatchewan (RGS = Richardson’s ground squirrels; DM = deer mouse; WHM = western harvest mouse; Prong = Pronghorn; Veg = vegetation; PDI = prey diversity index).

Prey

Landscapes poor in Richardson’s ground squirrels

Robertson June

n = 13

Bickner Woodrow June

n = 16

Neville June

n = 14

Gross

April n = 14

13-18 May n = 13

31 May n = 13

10 June n = 14

28 June- 12 July n = 47

May n = 11

June n = 15

Fre

quen

cy

(%)*

Mea

n V

olum

e %

SD

) F

requ

ency

(%

)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

RGS 3 (21.4)

23 (43.7)

2 (14.3)

14.3 (36.3)

2 (15.4)

15.4 (37.6)

1 (7.7)

7.7 (27.7)

4 (26.7)

28.6 (46.9)

6 (54.5)

54.5 (52.2)

9 (52.9)

55.8 (50.8)

4 (28.6)

28.6 (46.9)

4 (36.4)

33.6 (47.4)

10 (66.7)

59.5 (48.8)

DM 8 (21.4)

61.5 (50.6)

11 (78.6)

78.6 (42.6)

8 (61.5)

61.5 (50.6)

11 (84.6)

84.6 (37.6)

9 (60.0)

64.1 (49.6)

4 (36.4)

36.3 (50.3)

5 (31.3)

31.3 (47.9)

6 (42.9)

42.9 (51.4)

6 (54.5)

54.5 (52.2)

3 (20.0)

20 (41.4)

WHM 1 (7.7)

7.7 (27.7)

- - 1 (7.7)

7.7 (27.7)

- - 1 (6.7)

7.1 (26.7)

1 (9.1)

0.1 (0.3)

- - 1 (7.1)

7.1 (26.7)

1 (9.1)

9.1 (30.2)

1 (6.7)

6.7 (25.8)

Mule deer

- - - - - - - - - - - - - - 1 (7.1)

7.1 (26.7)

- - - -

Prong. - - - - - - - - - - - - - - - - - - 1 (6.7)

6.7 (25.8)

Birds 1 (7.7)

7.7 (27.7)

- - - - - - - - - - 1 (12.6)

12.5 (34.2)

2 (14.2)

14.3 (36.3)

- - 1 (6.7)

1.3 (5.2)

Insects - - - - - - - - 1 (6.7)

0.1 (0.5)

- - - - - - - - 1 (6.7)

5.4 (21.2)

Veg 1 (7.7)

0.1 (0.3)

- - - - - - - - 1 (9.1)

0.1 (0.3)

1 (6.3)

0.5 (2.0)

- - 1 (9.1)

2.7 (9.0)

- -

Other - - 1 (7.1)

7.1 (26.7)

2 (15.4)

15.4 (37.6)

1 (7.7)

7.7 (27.7)

- - 1 (9.1)

0.1 (0.3)

- - - - - - 1 (6.7)

0.3 (1.3)

PDI 1.744 0.945 1.548 0.774 1.213 1.893 1.610 1.712 1.602 2.070 * Some scats contained more than one food item.

23


Table 13. Frequencies and mean volumes (%) of food items in scats of red foxes inhabiting Richardson’s ground squirrel-rich landscapes, May-July 2010, southern Saskatchewan (RGS = Richardson’s ground squirrels; DM = deer mouse; WHM = western harvest mouse; Prong = Pronghorn; Veg = vegetation; PDI = prey diversity index).

Prey

Landscapes rich in Richardson’s ground squirrels

Thibault

House Den John Balas 28 June n = 14

May

n = 16 June

n = 15 6 June n = 14

27 June n = 14

15 May n = 14

28 May n = 13

15 June n = 14

24 June n = 23

22 July n = 15

Fre

quen

cy

(%)*

Mea

n V

olum

e %

SD

) F

requ

ency

(%

)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

Fre

quen

cy

(%)*

Mea

n V

olum

e %

(S

D)

RGS 13 (72.2)

78.6 (40.3)

10 (55.6)

66.1 (48.4)

12 (66.7)

65.7 (47.9)

11 (73.3)

73.3 (45.8)

7 (46.7)

50 (51.9)

4 (30.8)

30.8 (48.0)

11 (78.6)

78.6 (42.6)

18 (72.0)

78.3 (42.1)

8 (53.3

53.3 (51.6)

12 (75.0)

83.1 (36.2)

DM 3 (16.7)

18.8 (40.3)

- - - - 2 (13.3)

13.3 (35.2)

4 (26.7)

27.8 (45.8)

5 (38.5)

38.5 (50.6)

- - 2 (8.0)

8..7 (28.8)

5 (33.3)

33.3 (48.8)

- -

WHM - - 3 (16.7)

20 (41.4)

2 (11.1)

14.3 (36.3)

1 (6.7)

6.7 (25.8)

1 (6.7)

7.1 (26.7)

4 (30.8)

30.8 (48.0)

2 (14.3)

14.3 (36.3)

2 (8.0)

8.5 (28.4)

2 (13.3)

13.3 (35.2)

1 (7.1)

7.1 (26.7)

Birds - - - - - - - - 1 (6.7)

7.1 (26.7)

- - - - - - - - 1 (7.1)

7.1 (26.7)

Insects - - 1 (5.6)

0.2 (0.8)

3 (16.7)

19.7 (39.2)

- - 1 (6.7)

7.1 (26.7)

- - - - 2 (8.0)

1.9 (8.4)

- -

Veg 2 (11.1)

2.6 (10.0)

4 (22.2)

13.7 (35.1)

- - 1 (6.7)

6.7 (25.8)

1 (6.7)

7.1 (26.7)

- - 1 (7.1)

7.1 (26.7)

1 (4.0)

2.6 (12.5)

- - 1 (7.1)

0.4 (1.4)

OtherS - - - - 1 (5.6)

0.3 (1.1)

- - - - - - - - - - - - 1 (7.1)

2.2 (8.3)

PDI 1.123 1.617 1.406 1.238 2.067 1.576 0.945 1.402 1.399 1.319 * Some scats contained more than one food item.

24


Figure 7. Comparison of frequencies of ground squirrel remains in scats collected at different dens, from April to July 2010, southern Saskatchewan.

25


Table 14. Frequencies and mean volumes (%) of food items in red fox scats, June 2008 and 2009, southern Saskatchewan (RGS = Richardson’s ground squirrels; RBV = Red-backed vole; DM = deer mouse; WHM = western harvest mouse; SV = sagebrush vole; Jack = white-tailed jackrabbit; Deer = white-tailed and mule deer; Prong = Pronghorn; Veg = vegetation; PDI = prey diversity index; * Some scats contained more than one food item).

Prey

Mankota 2008

n = 41

Kincaid 2008 n = 41

Kincaid 2009 n = 21

Hazenmore 1 2009

n = 64

Hazenmore 2 2009

n = 17

Hazenmore 3 (DG) 2009

n = 47

Hazenmore 4 (John’s) 2009

n = 53

Aneroid 2009

n = 53

Ponteix (Balas) 2009

n = 86

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

RGS 30 (63.8)

68.8 (43.9)

35 (71.4)

76.3 (41.2)

13 (54.2)

61 (49.2)

50 (74.6)

78.1 (41.7)

14 (70)

82.2 (39.2)

36 (73.5

76.6 (42.8)

37 (66.1)

69.8 (46.3)

17 (60)

60.7 (49.7)

60 (67.4)

69.4 (46)

RBV 1 (2.1)

2.4 (15.6)

- - - - - - - - - - - - - - - -

DM 6 (12.8)

14.6 (35.8)

4 (8.2)

5.6 (22.1)

2 (8.3)

7.4 (24.0)

6 (9) 9.1 (28.5)

1 (5)

5.9 (24.3)

7 (14.3) 14.9 (36.0)

5 (8.9)

8.3 (27.0)

7 (24.1)

22.9 (41.7)

25 (28.1)

28.9 (45.4)

WHM 2 (4.3)

2.9 (15.9)

3 (6.1)

5 (21.8)

1 (4.2)

4.8 (21.8)

4 (6) 6.3 (24.4)

2 (10)

9.4 (27.5)

2 (4.1) 4.3 (20.4)

2 (3.6)

3.8 (19.2)

2 (6.9)

7.1 (26.2)

1 (1.1)

1.2 (10.8)

SV - - - - - - - - - - - - 1 (1.8)

1.3 (9.6)

- - - -

Jack - - - - - - - - - - - - 1 (1.8)

1.9 (13.7)

- - - -

Badger 1 (2.1)

1.2 (7.8)

- - - - - - - - - - - - - - - -

Deer 1 (2.1)

2.4 (15.6

- - 4 (16.7)

19 (40.2)

1 (1.5)

1.6 (12.5)

- - - - - - - - - -

Prong. - - - - 1 (4.2)

4.8 (21.8)

- - - - - - - - - - - -

Cattle - - - - - - - - - - - - 1 (1.8)

1.9 (13.7)

- - - -

Birds 2 (4.3)

0.7 (4.0)

2 (4.1)

4.9 (21.7)

- - 2 (3) 1.6 (12.5)

- - 1 (2) 0.1 (0.7) 5 (8.9)

8.7 (27.6)

2 (6.9)

7.1 (26.2)

- -

Insects 3 (6.4)

5.6 (22.1)

2 (4.1)

4.6 (20.6)

- - 1 (1.5)

1.6 (12.5)

2 (10)

0.2 (0.5) - - 2 (3.6)

3.8 (19.2)

- - 2 (2.2)

0.2 (1.7)

Veg 1 (2.1)

1.2 (7.8)

3 (6.1)

2.7 (14.1)

3 (12.5)

3.1 (9.5)

3 (4.5)

1.8 (12.1)

1 (5)

2.4 (9.7) 3 (6.1) 4.2 (19.9)

2 (3.6)

0.6 (4.1)

1 (3) 2.1 (11.3)

1 (1.1)

0.3 (3.2)

PDI 1.906 1.513 1.967 1.401 1.456 1.275 1.848 1.621 1.164

26


Table 15. Frequencies and mean volumes (%) of food items in scats of red fox populations inhabiting landscapes rich in Richardson’s ground squirrels, June 2010, southern Saskatchewan (RGS = Richardson’s ground squirrels; DM = deer mouse; WHM = western harvest mouse; Prong = Pronghorn; Veg = vegetation; PDI = prey diversity index).

* Some scats contained more than one food item. ** This sample was part of the 2010 ground squirrel-poor areas; it had a high frequency of ground squirrel remains in June and the den was located near dens of ground squirrel-rich areas.

Prey

Thibault 2010 n = 15

House Den 2010 n = 29

John’s 2010 n = 52

Ponteix (Balas) 2010 n = 14

Hazenmore 3 (DG)** 2010 n = 15

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

Freq

uenc

y (%

)*

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

Mea

n V

olum

e (S

D)

Mea

n V

olum

e (S

D)

Mea

n V

olum

e (S

D)

Freq

uenc

y (%

)*

Mea

n V

olum

e (S

D)

RGS 10 (55.6) 66.1 (48.4) 23 (69.7) 69.7 (46.1) 37 (68.5) 71.2 (45.7) 12 (75) 83.1 (36.2) 10 (66.7) 59.5 (48.8) DM - - 2 (6.1) 6.9 (25.8) 7 (13) 13.5 (34.5) - - 3 (20) 20.0 (41.4) WHM 3 (16.7) 20 (41.4) 3 (9.1) 10.3 (30.9) 6 (11.1) 11.5 (32.1) 1 (6.3) 7.1 (26.7) 1 (6.7) 6.7 (25.8) Prong - - - - - - - - 1 (6.7) 6.7 (25.8) Birds - - - - - - 1 (6.3) 7.1 (26.7) 1 (6.7) 1.3 (5.2) Insects 1 (5.6) 0.2 (0.8) 3 (9.1) 9.5 (28.6) 2 (3.7) 0.8 (5.6) - - 1 (6.7) 5.4 (21.2) Veg 4 (22.2) 13.7 (35.1) 1 (3.0) 3.4 (18.6) 2 (3.7) 3.1 (16.0) 1 (6.3) 0.4 (1.4) - - Othes & unknown - - 1 (3.0) 0.1 (0.7) - - 1 (6.3) 2.2 (8.3) 1 (6.7) 0.3 (1.3) PDI 1.617 1.542 1.437 1.319 2.070

27


4.4.3 Long-tailed weasel 2010 scat analysis – All weasel scats were collected in June during a toxicant study. In early June, latrines were found in study plots reported in Section 4.2.2. Poisoning was initiated on June 22, and with an increased of ground squirrel mortality, weasels moved in treated study plots; scats were then collected. Weasel was the dominant food item of 215 scats (Table 16). Mean volume of ground squirrel remains was 82.2 ( 38.2) % (Table 16). Synthesis of 2008-2010 data – In 2008, the proportion of scats with Richardson’s ground squirrel remains was significantly different among time periods (χ2 = 37.6, df: 2, P < 0.001). The proportion of scats with ground squirrel remains was significantly lower in August-September (G = 6.527, df: 1, P < 0.05) (Table 16). The mean volume of ground squirrel remains in scats was higher in June-July when juveniles were abundant. The proportion of June-July scats with Richardson’s ground squirrel remains was similar from one year to the other (χ2 = 2.9, df: 1, P > 0.05). Ground squirrel remains corresponded to approximately 63% of all prey items in 2009, and >79 % in 2008 and 2010. Mean volumes of ground squirrel remains in June-July scats were similar (F2, 365 = 1.324, P > 0.05) from 2008 to 2010 (Table 16). Richardson’s ground squirrels were the main prey. Also, there was a strong linear relationship (Y = - 0.0021 X + 2.752; r = - 0.953, P < 0.05) between prey diversity index and the frequency of ground squirrel remains, i.e., the index increased with a decrease of ground squirrel remains in scats. 4.0 DISCUSSION

In the past, habitat selection by badgers was associated with soil types (Apps et al. 2002), which impact on badgers’ digging activities, and the general presence of prey (Lindzey 2003). This study is the first to establish a strong relationship between the distribution of Richardson’s ground squirrels and badgers at landscape level, and between the abundance of ground squirrels and the establishment of hunting grounds at stand level. In a nutshell, badgers do not establish their home range and hunting grounds at random. In spring and summer, particularly when juvenile ground squirrels are born, badgers feed mostly on Richardson’s ground squirrels and undoubtedly have an impact on their population dynamics. However, when ground squirrels are less abundant or more difficult to catch, other food, namely small mammals, insects and carrion become more important. This is in agreement with previous findings (Messick and Hornocker 1981).

Red fox families have an impact on ground squirrel populations at den site. Their impact at stand level is more difficult to demonstrate. This is due to the fact that pups do not spend much time hunting until they are brought away from their den by their mother (Proulx, pers. obsrv.). Second, parents bring food to them on a regular basis (Vergara 2001), but their hunting occurs over large areas, often outside the boundaries of the fields encompassing the den site. Finally, their hunting and feeding largely reflects the time of day when they are active, which is highly variable among families. Nevertheless, in spring, foxes cached large amounts of ground squirrels near maternal dens. In June, foxes fed predominantly on ground squirrels. Such predation adds to ground squirrels losses resulting from other predators’ activities. Foxes are opportunistic foragers (Cypher 2003), and when ground squirrel densities decrease in importance, they switch prey.

28


This was obvious when we compared the food habits of families inhabiting landscapes rich in ground squirrels to those of families inhabiting landscapes poor in ground squirrels. However, it is noteworthy to mention that, in June, some families inhabiting areas that were relatively poor in ground squirrels still took advantage of the abundance of juvenile ground squirrels in adjacent landscapes.

Weasels were found to have a great effect on the population dynamics of voles (MacLean et al. 1974, Fitzerald 1977) and even impact on the amplitude of microtine cycles (Pearson 1971). This study is the first to show the impact of long-tailed weasels on the population dynamics of Richardson’s ground squirrels. Their impact is apparent in June when ground squirrels juveniles are active on surface. However, weasels are also known to kill fossorial rodents in their burrow system (Proulx 2000, Svendsen 2003) and they may impact on ground squirrels from the moment of their emergence in spring to the beginning of their hibernation period in late summer or later.

5.0 MANAGEMENT CONSIDERATIONS

This study showed that predators may impact individually or as a group on ground

squirrels, and they may play an important role in minimizing the risk of rodent population outbreaks (Witmer and Proulx 2010). Their impact on ground squirrel population dynamics is, however, a long-term process where predators numerically and functionally respond to a large amount of available prey. Predators must be given some time to impact on ground squirrel populations. Proulx et al. (2009) expressed their concerns regarding the use of some poisons and the secondary poisoning of ground squirrel predators. Within an Integrated Pest Management program, pesticides should be used to control ground squirrel concentrations that could generate population outbreaks. They should not be spread across landscapes, an approach which kills all rodents (and non-target species) and indirectly kill predators. Using pesticides in this manner delays predators’ response to an increase in prey abundance.

We noticed that badgers and weasels often established their dens and hunting rounds in ground squirrel-rich areas, particularly on ridges where prey populations are high because of easy digging. The control of ground squirrels in these ridges should be carefully carried out to not impact on predators. The use of mechanical killing devices may then be more appropriate than chemical control.

The major problem caused by badgers relates to their digging (Lindzey 2003). However, this study showed that badgers did not establish their hunting grounds at random, but rather selected areas with the highest abundance of ground squirrels (as suggested by burrow opening counts). Maintaining ground squirrel populations at low levels in crops and grasslands, without impacting on ridges, may keep badgers outside agricultural fields

Obviously, integrating predator conservation in Richardson’s ground squirrel population management will require diverse, site-specific approaches. Further investigations are needed to better determine when and how the control of ground squirrels must be conducted without endangering the survival of predators.

29


Table 16. Frequencies and mean volumes (%) of food items in long-tailed weasel scats, 2008-2010.

Food item 2008 2009 2010 April-May*

n = 35 June-July*

n = 135 August-September*

n = 26 June-July*

n = 18 June-July*

n = 215 Frequency (% of prey items)

Mean volume - %

(SD)

Frequency (% of prey items)

Mean volume - %

(SD)







MAMMALS Richardson’s ground squirrel

26 (59.1) 59.8 (46.4) 114 (79.7) 80.5 (38.6) 7 (25.0) 23.1 (42.9)

12 (63.2) 66.7 (48.5)

177 (80.8) 82.2 (38.2)

Sagebrush vole 5 (11.4) 11.1 (29.5) 6 (4.2) 4.4 (20.7)

9 (32.1) 34.6 (48.5)

- - - -

Deer mouse 3 (6.8) 6.3 (21.9)

3 (2.1) 2.0 (13.7)

4 (14.3) 15.3 (36.6)

4 (21.2) 22.2 (42.8)

25 (11.4) 11.6 (32.1)

Meadow vole 1 (2.3) 2.8 (16.7)

4 (2.8) 3.0 (17.0)

- - - - - -


- - 3 (2.1) 2.2 (14.8)

- - 1 (5.3) 0.3 (1.2)

7 (3.2) 3.3 (17.8)

BIRDS Birds - - 1 (0.7) 0.7

(8.6) 1 (3.6) 3.8

(19.6) - - - -

ARTHROPODS Insect - - 2 (1.4) 0.8

(8.6) 6 (21.4) 19.3

(40.2) - - 1 (0.5) 0.5

(6.8) VEGETATION

Grass-type/ oats/barley

9 (20.5) 18.0 (34.2)

10 (7.0) 5.9 (22.6)

1 (3.6) 3.8 (19.4)

2 (10.5) 10.8 (31.5)

8 (3.7) 2.4 (15.1)

OTHERS & UNKNOWN 1 (0.5) 0.03

(0.5) Prey Diversity Index

1.663 1.236 2.249 1.222 1.017

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6.0 ACKNOWLEDGMENTS We thank the Advancing Canadian Agriculture & Agri-Food in Saskatchewan

(ACAAFS) (as a Collective Outcome Project with AFC in Alberta), the Saskatchewan Ministry of Agriculture & Rural Development (Agriculture Development Fund) and Saskatchewan Association of Rural Municipalities (SARM) for funding this project. We are grateful to Scott Hartley and Henry Soita from Saskatchewan Agriculture, and Dale Harvey from SARM, for facilitating research logistics. We are grateful to producers Garth and Dale Gross, Orin Balas, Craig Knox, Glen Mackenzie, Laurent Thibault, Mike Thibault, Ronald Loverin, Tim Bickner for allowing us to conduct this project on their farmlands. We also thank Kenneth Rice from PowerSource Performance Inc. in Edmonton for the maintenance of the equipment.

7.0 LITERATURE CITED Apps, C. D., N. J. Newhouse, and T. A. Kinley. 2002. Habitat associations of American badgers in southeastern British Columbia. Cnadian Journal of Zoology 80: 1228-1239. Cypher, B. L. 2003. Foxes. Pages 511-546 in G. A. Feldhamer, B. C. Thompson, and J. A. Chapman, editors. Wild mammals of North America. Biology, management, and conservation. The Johns Hopkins University Press, Baltimore, Maryland, USA.

Fitzgerald, B. M. 1977. Weasel predation on a cycle population of the montane vole (Microtus montanus) in California. Journal of Animal Ecology 46: 367-397. Lindzey, F. G. 2003. Badger. Pages 683-691 in G. A. Feldhamer, B. C. Thompson, and J. A. Chapman, editors. Wild mammals of North America. Biology, management, and conservation. The Johns Hopkins University Press, Baltimore, Maryland, USA. MacLean, S. F., Jr. B. M. Fitzgerald, and F. A. Pitelka. 1974. Population cycles in arctic lemmings: winter reproduction and predation by weasels. Arctic and Alpine Research 6: 1-12 Messick, J. P., and M. G. Hornocker. 1981. Ecology of the badger in southwestern Idaho. Wildlife Monograph 76, 53 pages. Pearson, O. P. 1971. Additional measurements of the impact of carnivores on California voles (Microtus californicus). Journal of Mammalogy 52: 41-49. Proulx, G. 2000. Winter movements of long-tailed weasels in alfalfa fields inhabited by northern pocket gophers. Pages 13-15 in B. K. Calverley, editor. Proceedings First Alberta North American Waterfowl Management Plan Biodiversity Conference, Edmonton, Alta. Proulx, G. 2006. Using forest inventory data to predict winter habitat use by fisher Martes pennanti in British Columbia, Canada. Acta Theriologica 51: 275-282.

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Proulx, G. 2009. Conserving American Marten Martes americana winter habitat in sub-boreal spruce forests affected by Mountain Pine Beetle Dendroctonus ponderosae infestations and logging in British Columbia, Canada. Small Carnivore Conservation 41: 51-57. Proulx, G. 2011. The 2010 Richardson’s ground squirrel research and control program. Alpha Wildlife Research & Management Ltd. report submitted to Saskatchewan Association Rural Communities (SARM), Regina, Saskatchewan. 23 pages. Proulx, G., N. MacKenzie, K. MacKenzie, B. Proulx, and K. Stang. The Richardson’s ground squirrel (Spermophilus richardsonii) research & control program 2009-2010. Alpha Wildlife Research & Management Ltd. report submitted to Saskatchewan Association Rural Communities (SARM), Regina, Saskatchewan. 50 pages. Proulx, G., N. Mackenzie, B. Proulx, K. Mackenzie, and K. Walsh. 2009. Relationships among predators, prey and habitat use in southern Saskatchewan, 2008. Alpha Wildlife Research & Management Ltd. report submitted to Saskatchewan Agriculture Development Fund, Regina, Saskatchewan. 28 pages. Proulx, G., D. K. Onderka, A. J. Kolenosky, P. J. Cole, R. K. Drescher, and M. J. Badry. 1993. Injuries and behavior of raccoons (Procyon lotor) captured in the Soft CatchTM and the EGGTM traps in simulated natural environments. Journal of Wildlife Diseases 29: 447-452. Siegel, S. 1956. Nonparametric statistics for the behavioral sciences. McGraw-Hill, New York, USA.

Sokal, R. R., and F. J. Rohlf. 1981. Biometry. 2nd edition. W. H. Freeman and Co., San Francisco, California, USA. Svendsen, G. E. 2003. Weasels and black-footed ferret. Pages 650-661 in G. A. Feldhamer, B. C. Thompson, and J. A. Chapman, editors. Wild mammals of North America. Biology, management, and conservation. The Johns Hopkins University Press, Baltimore, Maryland, USA.

Vergara, V. 2001. Comparison of parental roles in male and femal red foxes, Vulpes vulpes, in southern Ontario. Canadian Field-Naturalist 115: 22-33.

Witmer, G., and G. Proulx. 2010. Rodent outbreaks in North America. Pages 253-267 in G. R. Singleton, S. R. Belmain, P. R. Brown, and B. Hardy, editors, Rodent outbreaks – ecology and impacts. International Rice Research Institute, Metro Manila,Philippines.

Zar, J. H. 1999. Biostatistical analysis. Prentice-Hall, Englewood Cliffs, New Jersey, USA.

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APPENDIX I

Badger Taxidea taxus Cattle Bos taurus Coyote Canis latrans Deer mouse Peromyscus maniculatus Gray partridge Perdrix perdrix Long-tailed weasel Mustela frenata Mule deer Odocoileus hemionus Pronghorn Antilocapra americana Red fox Vulpes vulpes Richardson’s ground squirrel

Spermophilus richardsonii

Sagebrush vole Lemmiscus curtatus Snowshoe hare Lepus americanus Western harvest mouse Reithrodontomys megalotis White-tailed deer Odocoileus virginianus White-tailed jackrabbit Lepus townsendii

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APPENDIX II - RELATIONSHIPS AMONG PREDATORS, PREY AND HABITAT

USE IN SOUTHERN SASKATCHEWAN, 2008

Report prepared by

Gilbert Proulx, Neil Mackenzie, Benjamin Proulx, Keith Mackenzie, and Kara Walsh

and submitted to

Saskatchewan Agriculture Development Fund

Regina, Saskatchewan 19 February 2009

34


SUMMARY

A better understanding of the predator-prey relationships in agricultural ecosystems could lead to a predator conservation program that could support producers in their control of Richardson’s ground squirrel (Spermophilus richardsonii) population outbreaks. The objectives of this study related to three predator species: Badger (Taxidea taxus): 1. Determine the density, sex, and age structure and other characteristics of the badger

population; 2. Investigate movements, activity, and social organization of badgers; and 3. Gather data on food habits to assess the role of the badger as a predator of Richardson’s

ground squirrels. Long-tailed Weasel (Mustela frenata): 1. Gather data on food habits to assess the role of the long-tailed weasel as a predator of

Richardson’s ground squirrels; and 2. Estimate the distribution of the species within study areas used for other investigations (e.g.,

toxicant assessments) in order to conduct a study of the long-tailed weasel population in late winter-early spring 2009.

Coyote (Canis latrans): 1. Gather data on food habits to assess the role of the coyote as a predator of Richardson’s

ground squirrels. The study was carried out in southern Saskatchewan, in the Rural Municipalities of Mankota, Glen McPherson, and Pinto Creek. Predators were observed, and their scats were collected, mostly in grasslands dominated by crested wheat grass (Agropyron crustatum), and in alfalfa fields (Medicago spp.). Data on radio-tracked badgers occurred north of Hazenmore, in a pasture with various grasses and buckbrush (Ceanothus spp.), and surrounded by cultivated fields (mustard and wheat). Badger In spring and summer, the density of badgers in grasslands was estimated at 1 adult/quarter section (64 ha). One female adult was radio-tracked from September to December, at which time it became inactive due to a cold front. Her home range of 1.04 ha (2.2% of the pasture-annual crop complex) included 4 hunting grounds, 1 escape area, and 5 dens interconnected by trails. On average, the density of ground squirrel and badger holes was significantly higher (P < 0.05) in badger hunting grounds than in control plots. There was a significant (r = 0.97, P < 0.0005) relationship between the density of badger holes/ha and the density/ha of Richardson’s ground squirrel holes/ha. Badgers displayed zigzag and back-and-forth movements in their hunt for ground squirrels. Scat analyses indicated that, from April to July, mammal remains consisted only of Richardson’s ground squirrels, and they were significantly (P = 0.0002) more abundant than in August-September. From August to November, the food habits of the badgers became more diversified, including several small mammals, insects and vegetation.

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Long-tailed weasel The density of long-tailed weasels in grasslands was estimated at 1 adult/quarter section in the spring and 1 family/half section in spring and summer. From 18 to 21 June, the average number of juvenile ground squirrels (7 2.2 juveniles; range of 4 to 9) captured in 4 study plots with large weasel latrines was significantly (P < 0.005) lower than that of study plots (12.5 : 3.3; range of 10 to 20) without latrines. On average, weasels controlled 44% of juvenile ground squirrel populations. From April to July, Richardson’s ground squirrels were the predominant prey, being found in 85% of scats. In August-September, however, small mammals and insects were the most frequent food items present in scats. Coyote Richardson’s ground squirrel remains were found in 50% of scats in April-May and June-July, but dropped to 14.3 % in fall. From April to July, small mammal remains were as important as ground squirrel items in frequency and volume. In fall, small mammals and ungulates were predominant in the scats. Coyotes started to feed more on insects starting in mid-summer. Richardson’s ground squirrels were most important food items in the spring and summer diets of badgers, long-tailed weasels, and coyotes. Data suggest, however, that badgers and long-tailed weasels may have a greater impact on ground squirrel populations than coyotes. More research is required to quantify the impact of these predators on ground squirrel populations. We recommend that the predator-prey relationships be further investigated by 1) analyzing scats of badgers, weasels and coyotes collected at different times of the year, and 2) monitoring the activities of badgers and long-tailed weasels, and the survival of tagged ground squirrels, in specific areas and at different times of the year.

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1.0 INTRODUCTION

A better understanding of the predator-prey relationships in agricultural ecosystems could lead to a predator conservation program that could support producers in their control of Richardson’s ground squirrel (Spermophilus richardsonii) population outbreaks. Along with chemical and mechanical control methods, predation may play an important role in reducing the densities of fossorial rodents. For example, although Proulx (1997) showed that it was possible to control northern pocket gopher (Thomomys talpoides) populations with trapping, long-tailed weasel (Mustela frenata) predation played an important role in the control of this rodent in summer (Proulx and Cole 1998), and particularly in winter when trapping cannot be carried out (Proulx 2005). Long-tailed weasels feed almost exclusively on small rodents, but their impact on Richardson’s ground squirrels is poorly known (see review by Svendsen 2003). Michener (in Bernard et al. 2004) estimated that weasels could reduce juvenile Richardson’s ground squirrel numbers by up to 50% in one season through infant predation, although data are required to confirm this estimation. Badgers’ large excavations have an impact on producers, which may counteract the benefits resulting from predation. As a result, badgers are shot or killed on roads (Messick and Hornocker 1981). More information on their role as predators and on their movements is required in order to develop a conservation program with producers. Michener (2000), during a study of ground squirrels, recorded notes about badger kills, and concluded that this predator could impact on hibernating animals, and on infants. However, little is known on the behaviour of this predator during ground squirrel population outbreaks. Finally, although Michener (1979) reported presence of ground squirrel remains in coyote (Canis latrans) scats, the importance of ground squirrels in the diet of this predator from spring to fall is poorly known. Coyotes are shot by producers fearing for their calves (Proulx, 2008, personal notes). Overall, the role that mammal predators play in the control of Richardson’s ground squirrels needs to be evaluated. The objectives of this study related to three predator species: Badger: 1. Determine the density, sex, and age structure and other characteristics of the badger

population; 2. Investigate movements, activity, and social organization of badgers; and 3. Gather data on food habits to assess the role of the badger as a predator of Richardson’s

ground squirrels. Long-tailed Weasel: 1. Gather data on food habits to assess the role of the long-tailed weasel as a predator of

Richardson’s ground squirrels; and 2. Estimate the distribution of the species within study areas used for other investigations (e.g.,

toxicant assessments) in order to conduct a study of the long-tailed weasel population in late winter-early spring 2009.

Coyote: 1. Gather data on food habits to assess the role of the coyote as a predator of Richardson’s

37


ground squirrels.

2.0 STUDY AREA The study was carried out in southern Saskatchewan, in the Rural Municipalities of Mankota, Glen McPherson, and Pinto Creek (Figure 1). Predators were observed, and their scats were collected, mostly in grasslands dominated by crested wheat grass (Agropyron crustatum), and in alfalfa fields (Medicago spp.). Data on radio-tracked badgers occurred north of Hazenmore, in a pasture with various grasses and buckbrush (Ceanothus spp.), and surrounded by cultivated fields (mustard and wheat).


38


3.0 METHODS

3.1 BADGER

The density of badgers was determined over specific areas including Proulx et al.’s (2009) study plots for the evaluation of toxicants. The distribution of animals was determined through animal search where signs of activity had been noted, encounters when traveling between study plots, and the discovery of dead animals. The age structure of the population was not determined due to delays in the initiation of the trapping and radio-telemetry program. The capture of badgers was postponed until summer because of delays in the production of radio-transmitters. Badgers were captured in baited cage traps (Woodroffe et al. 2005), and pole snares (Powell and Proulx 2003). Traps were checked daily. Trapped badgers were transferred in a carrying cage, and anaesthetized in a veterinary clinic with isoflurane. Animals were radio-tagged by implanting a transmitter between shoulder blades. Radio-transmitters were equipped with ≥ 36-month-long batteries, and activity and mortality features. Two juveniles captured in June were kept in captivity for approximately 2 weeks to ensure that radio-transmitters did not interfere with their behavior before being released near their capture site in a pasture north of Hazenmore,. One adult female captured in September was released the same day of the operation. Because badgers are victims of poisoning (Proulx et al. 2009), shooting and traffic (Messick and Hornocker 1981), and such fatalities amount to incomplete databases and loss of equipment and money, it was decided to gather detailed information on the activities and the home range of one adult female before capturing other adults. This information would then allow us to better define selection criteria for the identification of relatively safe study areas where extensive data would be collected in the future. Animals were located on a daily basis until their death in the case of the juveniles, or the development of a cold front in the case of the female, which became inactive in December. Once the female was located with radio-telemetry, spotlighting (Jolly 1976, Ralls and Eberhardt 1997, Ruette et al. 2003) was used to describe the animal’s location and the type of activity it was engaged in, and to record the presence of neighboring adult badgers. Disturbance of the animal was minimized by staying at least 100 m away from it, and avoiding centering the light beam on its head. The day after each radio-telemetry and spotlighting session, we visited the areas where the animal was observed to identify new digging activity and quantify the extent of the movements using tracks. Radio-telemetry locations, spotlighting observations, and field investigations allowed us to identify the extent of the hunting grounds, which are defined as areas of intensive hunting activities repeatedly used for several days. The location and size of the animal’s hunting grounds, dens, trails and escape areas were plotted to scale on 1:5000 orthophotos, and interconnected (Messick and Hornocker 1981; Proulx and Gilbert 1983) to provide a realistic description of the home range (Powell 2000). The number of Richardson’s ground squirrel and badger holes within the hunting grounds was counted. They were compared to those of 0.42 ha control plots located at random 30 m on each

39


side of the hunting ground, unless they overlapped with another hunting ground. Then, only one control plot was inventoried. Food samples came from two sources: 1) scats from captured badgers, and 2) scats collected at burrows and predation sites within and between study plots (e.g., prairie roads) used for the evaluation of toxicants (Proulx et al. 2009). Scat analyses were conducted at Alpha Wildlife Research & Management Ltd. laboratory in Sherwood Park, Alberta. Scats were dated, bagged, and kept frozen until processing. They were soaked overnight in a mild water-bleach solution, washed through a sieve, and oven-dried at 75oC. Scats were analyzed according to Chandler (1916), Adorjan and Kolenosky (1969) and Moore et al. (1974). 3.2 LONG-TAILED WEASEL

Scats from weasels that were captured during Proulx et al.’s (2009) Richardson`s ground squirrel sessions, and scats found within and between study plots (e.g., prairie roads, rock piles) used for the evaluation of toxicants, were collected. They were analyzed at Alpha Wildlife Research & Management Ltd. laboratory.

The distribution of weasels was determined within Proulx et al.’s (2009) study plots for the evaluation of toxicants. It was based on observations and accidental captures in traps set for ground squirrels. A male weasel was captured in the pasture inhabited by radio-tracked badgers. It was radio-collared and released in November. However, the animal broke its collar the same day. Thereafter, weasel trapping was unsuccessful due to a cold front. The impact of long-tailed weasel predation on ground squirrel juvenile populations was evaluated in summer during toxicant studies. In mid-June, Proulx et al. (2009) initiated a capture program for juvenile Richardson`s ground squirrels using 8 Tomahawk (15 x 15 x 48 cm; Tomahawk Live Trap, Tomahawk, Wisconsin) live-traps baited with peanut butter on bread in each study plot. Capture success from 18 to 21 June were used to evaluate juvenile ground squirrel populations and assess the suitability of study plots for toxicant studies (Proulx et al. 2009). In 4 study plots, visual observations and the presence of latrines with large accumulations of scats deposited in the space of about 0.1m2 confirmed residency by weasels. The average capture rate of juveniles in these 4 study plots was compared to that of study plots without extended weasel activities at time of testing. 3.3 COYOTE

Scats ≥ 18 mm in diameter, found within and between study plots (e.g., prairie and secondary roads) used for the evaluation of toxicants, were classified as coyote scats (Green and Flinders 1981, Reed et al. 2004). They were collected and analyzed in Alpha Wildlife laboratory.

3.4 STATISTICS

Comparisons between the average numbers of Richardson’s ground squirrel and badger holes in

40


badger hunting grounds and control areas, and between the size of juvenile populations in study plots with and without weasel activity, were carried out with the Student’s t-test (Zar 1999). Comparisons of the frequencies (chi-square and Fisher tests; Siegel 1956) and mean volume per scat (Student’s t-test, analysis of variance followed by the Tukey test; Zar 1999) of remains between different periods of the year were made (Proulx et al. 1987). A simple linear regression model was used to determine the relationship between some variables. A 0.05 level of significance was used for all tests.

4.0 RESULTS

4.1 BADGER

4.1.1 Density of adult badgers in study plots

Observations on the distribution of badgers in study plots and immediate surroundings suggest a density of 1 adult badger/quarter section (64 ha) at different times of year (Table 1). Table 1. Distribution and density of badgers in Proulx et al.’s (2009) study plots.

Time of Year

Number of badgers

Size of the area

Vegetation Location

Spring 1 Quarter Section

Native grassland dominated by crested wheat grass and buckbrush

R. Kress

1 Quarter Section

Native grassland dominated by crested wheat grass and buckbrush

R. Schafer

1 Quarter Section

Native grassland with crested wheat grass, slender wheat grass (Elymus trachycaulus), sage (Artemisia spp.), blueberry (Vaccinium spp.), brittle prickly-pear cactus (Opuntia fragilis), and prickly-pear cactus (Opuntia polyacantha).

B. Switzer

1 Quarter Section

Native grassland dominated by crested wheat grass R. Moen

Summer 2 Half Section

Native grassland with crested wheat grass, sage, blueberry, rose (Rosa spp.).

O. Ballas

Fall 4 Section Native grassland dominated by crested wheat grass and buckbrush, and annual crops.

N. Mackenzie G. Gross

4.1.2 Capture and fate of badgers

Three badgers were captured during the 2008 study program: 2 male juveniles and 1 female adult. The juvenile badgers (approximately 2.5 months old) were captured on 23 June with a snare pole while they were travelling on a dirt road north of Hazenmore. The same day, one transmitter was implanted in one of the animals (Figure 2a,b), which was kept in a small enclosure until July 6 to ensure that the transmitter did not impact on its behavior. On 6 July, a transmitter was implanted in the other juvenile. Both animals were released on 9 July near their original site of capture

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(Figure 2c,d), in a pasture without poisoning or shooting activities. The same day, the animals adopted an abandoned badger burrow on the east side of the pasture, and they were observed investigating the pasture and an adjacent wheat field where they appeared to feed on Richardson’s ground squirrels (Figure 2e). Both the animals disappeared on 14 July. The remains of one juvenile (Figure 3a) were discovered on 25 September approximately 30 m north of its burrow with holes in the thoracic region (Figure 3b) that appeared to have been made by the talons of a bird of prey. The regurgitation pellet of a large bird of prey, possibly an owl, with the remains of a young badger, was found along the west side of the pasture, approximately 400 m from the badger’s burrow (Figure 3c,d). A long-eared owl (Asio otus) with a nest in a nearby barn (Figure 3e) was also observed sweeping down on the female adult that was captured in September. The juvenile badgers may have been killed by this bird of prey.

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Figure 2 a, b – Implantation of a transmitter; c, d – Release of juvenile badgers; e – badgers established themselves in an abandoned burrow on the east side of the pasture.

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Figure 3 a, b – Remains of a young badger with perforations in the thoracic region; c, d – Partially opened regurgitation pellet with badger claws, bones and hair; e – This long-eared owl has been seen attacking a female adult in the pasture. One female adult (named A) was captured on September 29 in a cage trap set at a rock pile (Figure 4a,b), equipped with an implant transmitter the same day, and released at its capture site (Figure 4c). It has been monitored from 29 September to 28 November. Since December, the animal has not been very active, and it spent most of the time underground due to very cold weather ( -20o C). Figure 4. Capture of an adult female badger at a rock pile (a, b), and release of the animal with an implanted transmitter (c).

4.1.3 Home range of the female adult badger

The female’s home range was located in a pasture (31.4 ha)-annual crop (16.2 ha) complex4. The home range corresponded to a series of small areas (Figure 5): 5 burrows to sleep, 4 of them located in 4 hunting grounds that were interconnected by cow trails or badger trails along fences, and escape cover in buckbrush where the animal found refuge in 4 holes during bad weather or when it was surprised by our vehicle. The southernmost den (no. 5) was used once after releasing the badger, and another time when another adult badger was foraging nearby. Hunting grounds ranged in size from 0.10 to 0.38 ha. The hunting grounds and the trails used by the badger, amounted to 1.04 ha: 0.73 ha (70.2%) in the pasture and 0.31 ha (29.8%) in the annual crops 4 The pasture-annual crop complex corresponded to an area that included the female badger activities, but not those of neighbouring badgers.

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(Table 2). Overall, the home range of the female badger represented only 2.2% of the pasture-annual crop complex (2.3% of the pasture area, and 1.9% of the annual crop area).

Figure 5. Location of sites used by the female badger

within a pasture-annual crop complex.

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Table 2. Components of the female badger home range, September-December 2008.

Home range components Habitat type (ha) Pasture Annual crop

Hunting grounds 1 2 3 4

0.08

0.30

0.23 - 0.22 - 0.09 0.01

Cow and fence trails and escape area 0.11 Total 0.73 0.31

4.1.4 Adult neighbors

Badger A had three neighbors of unknown sex: 1 to the southeast (B), 1 to the west (C), 1 to the north (D). There was no overlap between the areas where badgers were active. Observed distances between the female badger and its neighbors ranged from 200 to 800 m. While observing the female’s activities, data were also gathered on badgers C and D.

4.1.5. Badger and ground squirrel holes in hunting grounds vs. control plots

Five hunting grounds (Figure 6) were identified: 4 for badger A, and 1 for badger C. The number of ground squirrel and badger holes was consistently higher in hunting grounds than in their corresponding control plots (Table 3). On average, the density of ground squirrel holes was significantly higher (t = 3.18, df: 5, P < 0.05) in badger hunting grounds than in control plots (Table 3). Likewise, the density of badger holes was higher (t = 2.71, df: 5, P < 0.05) in hunting grounds than in control plots (Table 3).

Figure 6. Hunting grounds: a) no. 1 with flags identifying Richardson’s ground squirrel and badger holes; and b) no. 2, fall 2008.

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Table 3. Densities of ground squirrel and badger holes in badger hunting grounds and in control plots, September-November 2008. Badger Number Number of ground

squirrel holes Density of ground squirrel holes/ha

Number of badger holes

Density of badger holes/ha

Hunting ground

Control plot

Hunting ground

Control plot

Hunting ground

Control plot

Hunting ground

Control plot

A 1 404 1063.2 27 71.1 70 166.7 8 19 15 35.7 4 9.5

2 463 2013.0 43 187.0 73 173.8 12 28.6 114 271.4 11 26.2

3 133 604.5 7 31.8 94* 223.8 3 7.1

4 155 1550.0 13 130.0 212* 504.8 17 40.5

C 5 75 500.0 10 66.7 75* 178.6 10 23.8

-

-

1146.1

222.1

-

-

97.3

22.1

Standard deviation - -- 638.8 144.0 - - 61.3 11.5 *Only 1 control plot could be established.

4.1.6 Relationship between the densities of badger and ground squirrel holes

A significant relationship existed between the density of badger holes/ha and the density/ha of Richardson’s ground squirrel holes/ha. The linear regression between densities was Y = 11.1 X + 14.23 (r = 0.97, P < 0.0005) (Figure 7).

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Figure 7. Relationship between the densities of badger and Richardson’s ground squirrel holes/ha, fall 2008.

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4.1.7 Badger hunting movements

Two types of hunting movements were recorded while observing 3 different badgers: 1) zigzag; and 2) back-and-forth. Zigzag movements – From September to November, in hunting grounds nos. 1, 2 and 3, badger A made tight zigzags along the pasture-annual crop border, and investigated Richardson’s ground squirrel burrows on each side of the fence for distances of up to 150 m. The animal walked with its head down, smelling ground squirrel holes, and digging small, shallow holes at or in between the ground squirrel burrows (Figure 8).

Figure 8. Badger A dug out a series of small, shallow holes while zigzagging along fences.

In October, badger A made 8 deep (> 3 m) zigzags in hunting ground no. 2 (Figure 9). All along the zigzags, the badger investigated ground squirrel holes.

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Figure 9. Deep zigzag movements in hunting ground no. 2.

Back-and forth movements – Two types of back-and-forth movements were observed: 1) between two end points only; and 2) between one point and many others. On 18 October, badger B made repetitive, straight movements between two of its holes, which were 6-m apart, all the time sniffing the ground. At each hole, he went down and returned quickly above ground always moving a significant amount of dirt and widening both holes. On 7 October, badger C moved back-and forth between its hole and 5 ground squirrel holes. The badger moved straight to the first ground squirrel hole and sniffed it, returned to its main hole, went down, and quickly returned above ground to initiate the same type of movement with the second ground squirrel hole (Figure 10). The badger did not go back to previous ground squirrel holes, and it investigated systematically each ground squirrel hole, in a consecutive manner, without missing any of them. After investigating the 5 ground squirrel holes, the badger retired to a den located 130 m away. Badger A investigated ground squirrel holes in the same manner in hunting ground 2.

Figure 10. Back-and-forth movements between a badger hole and a series of Richardson’s ground squirrel holes.

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4.1.8 Scat analyses

There was a significant difference (X2 = 16, df: 3, P < 0.01) in the frequency of Richardson’s ground squirrel remains vs. other food items from one period to the other (Table 4). From April to July, mammal remains consisted only of Richardson’s ground squirrels, and they were significantly more frequent than in August-September (Fisher, P = 0.0002). From August to November, the food habits of the badgers became more diversified, including several small mammals, insects and vegetation (possibly ingested when foraging for insects). The presence of white-tailed deer (Odocoileus virginianus) in an October-November scat is probably the result of scavenging. A few badger hairs were present in scats, probably the result of grooming. When ground squirrel remains were present in scats, they represented 100% of the contents. In October-November, when mammals and insects were important food items, there was no significant difference (t = 0.35, P > 0.05) between the mean volumes of mammals ( = 59.7 ± 46.6%) and insects ( = 68.3 ± 37.7%). Table 4. Frequencies and relative volumes (%) of food items in badger scats, spring-fall 2008.

Food item April-May n = 9

June-July* n = 7

August-September* n = 8

October-November* n = 9

Frequency (%)

Mean volume

- %

Frequency (%)

Mean volume

- %

Frequency (%)

Mean volume

- %

Frequency (%)

Mean volume

- % MAMMALIA


9 (90) 100 5 (71.4) 100 4 (50) 100 2 (22.2) 100

Sagebrush vole (Lemmiscus curtatus)

2 (22.2) 30

Deer mouse (Peromyscus maniculatus)

1 (11.1) 98

Badger 1 (14.3) 1 1 (12.5) 1 2 (22.2) 62** White-tailed deer (Odocoileus virginianus)

1 (11.1) 100

AVES Gray partridge (Perdix perdix)

1 (10) 100

ARTHROPODA Grasshopper 4 (50) 94.3 5 (55.6) 81.6 Beetles 1 (12.5) 2 Field cricket (Gryllus pennsylvanicus)

1 (11.1) 2

VEGETATION Grass-type 1 (14.3) 89 3 (37.5) 6.7 1 (11.1) 2

MISCELLANEOUS Pebbles 1 (11.1) 5

UNKNOWN Bone 1 (14.3) 10 1 (11.1) 1 * Some scats contained more than one food item. * * Scats with few contents.

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4.2 LONG-TAILED WEASEL

4.2.1 Density of long-tailed weasels in study plots

Observations on the distribution of long-tailed weasels in study plots and their immediate surroundings suggest a density of a minimum of 1 adult weasel/quarter section (64 ha) in the spring, and 1 family/half section (128 ha) in spring and summer (Table 5). Table 5. Distribution and density of badgers in Proulx et al.’s (2009) study plots.

Time of Year

Number of weasels

Size of the area

Vegetation Location

Spring >4 animals (family)

> 64 ha Native grassland dominated by crested wheat grass and buckbrush

R. Kress

1 Quarter Section

Seeded grassland with sparse and patchy vegetation including crested wheat grass and intermediate wheat grass (Agropyron intermedium).

R. Schafer

Summer >4 animals (family)

Half Section

Seeded grassland dominated by crested wheat grass. O. Ballas

Fall >4 animals (family)

Section Seeded grassland dominated by crested wheat grass and alfalfa field.

O. Ballas C. Knox

4.2.2 Estimation of predation based on juvenile ground squirrel trapping

From 18 to 21 June, the average number of juvenile ground squirrels (7 2.2 juveniles; range of 4 to 9) captured in 4 study plots with latrines was significantly lower than that of study plots (12.5 3.3; range of 10 to 20) without latrines (t = 3.11, df: 15, P < 0.005). On average, weasels controlled 44% of juvenile ground squirrel populations in these 4 study plots. Scats collected in latrines from these 4 study plots were collected and analyzed. In each of these study plots, Richardson’s ground squirrels were the predominant prey (Table 6). In Study Plot no. 13, where spring (April-May) and summer (June) scats were collected, the frequency of Richardson’s ground squirrel remains in the scats was the same, i.e. 77.8% (Table 6). Table 6. Frequency of food items in spring and summer in long-tailed weasel scats from 4 study plots with latrines, 2008.

Food item Frequency (%) in weasel scats Study Plot # 10 Study Plot # 13 Study Plot # 15 Study Plot # 16

April-May n - 9* - - Richardson’s ground squirrel

- 7 (77.8) - -

Sagebrush vole 3 (33.3) - - June

n 14* 9 25* 8* Richardson’s ground 10 (71.4) 7 (77.8) 25 (100) 8 (100)

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squirrel Sagebrush vole 2 (22.2) Meadow vole (Microtus pennsylvanicus)

4 (28.6) 1 (12.5)

Vegetation 3 (21.4) 3 (12) 1 (12.5) *Some scats had more than one food item. 4.2.3 Scat analyses There was a significant difference (X2 = 26.8, df: 4, P < 0.001) in the frequency of Richardson’s ground squirrel, small mammals and birds, and insect and vegetation remains from April to September (Table 7). From April to July, Richardson’s ground squirrels were the predominant prey, being found in 85% of scats. In August-September, however, small mammals and insects were the most frequent food items present in scats. The mean volume of the Richardson’ ground squirrel, small mammal and bird, and insect and vegetation was significantly different in June-July only (F2, 65= 4.25, P < 0.05). On average, Richardson’s ground squirrel items were significantly more important (Tukey, P < 0.05) than those of insects and vegetation, but similar (P > 0.05) to those of voles. There was no significant difference from one period to the other among mean volumes of ground squirrel remains (F2,79= 1.17, P > 0.05), voles and mice (F2,26= 2.78, P > 0.05), and vegetation (F2,17= 0.88, P > 0.05).

Table 7. Frequencies and relative volumes (%) of food items from April to September in weasel scats from southern Saskatchewan, 2008.

Food item April-May* n = 26

June-July* n = 62

August-September* n = 26

Frequency (%)

Mean volume -

%

Frequency (%)

Mean volume -

%

Frequency (%)

Mean volume -

% MAMMALS


22 (84.6) 81.9 53 (85.5) 92.5 7 (26.9) 85.9

Sagebrush vole 5 (19.2) 80 4 (6.5) 100 9 (34.6) 100 Meadow vole 1 (3.9) 100 4 (6.5) 87.5 Deer mouse 4 (15.4) 99.5 Northern grasshopper mouse (Onychomys leucogaster)

1 (3.9) 100

AVES Gray partridge (Perdix perdix)

1 (3.9) 100

ARTHROPODA Field cricket (Gryllus pennsylvanicus)

4 (15.4) 75.5

Unknown 2 (7.7) 100 VEGETATION

Grass-type 6 (23.1) 66.3 7 (11.3) 64 1 (3.9) 99 * Some scats contained more than one food item.

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4.3 COYOTE

4.3.1 Scat analyses

There was a significant difference (Fisher, P = 0.04) in the frequency of Richardson’s ground squirrel and other prey items between April-July and October-November (Table 8). Richardson’s ground squirrel remains were found in 50% of scats in April-May and June-July, but dropped to 14.3 % in October-November. From April to July, small mammal remains were as important as ground squirrel items in frequency and volume. In fall, small mammals and ungulates were predominant in the scats. Coyotes started to feed more on insects starting in mid-summer (Table 8). Table 8. Frequencies and relative volumes (%) of food items from spring to fall in coyote scats from southern Saskatchewan, 2008.

Food item April-May* n = 8

June-July* n = 6

October-November* n = 7

Frequency (%)

Mean volume -

%

Frequency (%)

Mean volume -

%

Frequency (%)

Mean volume -

% MAMMALS


4 (50) 100 4 (66.7) 82.5 1 (14.3) 50

Sagebrush vole Western harvest mouse (Reithrodontomys megalotis)

3 (37.5) 67.7

Deer mouse 1 (12.5) 100 Northern grasshopper mouse (Onychomys leucogaster)

1 (16.7) 5 3 (42.9) 6.7

Brown rat (Rattus norvegicus)

1 (14.3) 95

Badger 2 (33.3) 85 2 (28.6) 3 White-tailed deer 1 (14.3) 90 Pronghorn (Antilocarpa americana)

1 (14.3) 50

Cattle (Bos taurus) 1 (14.3) 100 AVES

Gray partridge (Perdix perdix)

ARTHROPODA Grasshopper 1 (16.7) 95 3 (42.9) 62.7 Unknown

VEGETATION Grass-type and seeds 2 (25) 48.5 1 (14.3) 99

MISCELLANEOUS Pebbles 2 (28.6) 2

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* Some scats contained more than one food item.

5.0 DISCUSSION Although differential digestibility of various types and sizes of prey may bias scat analyses (e.g., Floyd et al. 1978, Kelly and Garton 1997), there can be little doubt that Richardson’s ground squirrels were important food items in the spring and summer diets of badgers, long-tailed weasels, and coyotes. Data suggest, however, that badgers and long-tailed weasels may have a greater impact on ground squirrel populations than coyotes. 5.1 BADGER

Locally, badger densities may vary with prey concentrations (Lindzey 2003). Our estimate of 1 badger per 64 ha (1/0.6 km2) is similar to densities of 2/km2 in northwestern Wyoming (Minta and Mangel 1989, Minta 1993), and 0.8-1.1 km2 in south-central Wyoming (Goodrich and Buskirk 1998). Likewise, home range size varies considerably within and among regions (Lindzey 2003). In most previous studies, badger home ranges were determined by connecting known locations, and therefore including large areas found in between observations (Lindzey 1978, Lampe and Sovada 1981). In this study, spotlighting allowed us to pinpoint specific areas used by the female badger in the fall. As a result, the fall home range corresponded to only 1.04 ha, or 2.2% of the pasture-annual crop complex. This is markedly less than home range sizes of 300 ha reported by Sargeant and Warner (1972) and Lampe and Sovada (1981) for the same time period. In the fall, our female badger was quite sedentary, as it was noted for females in other studies (Sargeant and Warner 1972, Lindzey 1978, Lampe and Sovada (1981). The female badger stayed several consecutive days in the same area, and reused the same dens of its 4 hunting grounds. Locally, these hunting grounds had the highest levels of ground squirrel activity as suggested by the density of holes/ha. Also, the density of badger holes/ha was significantly correlated with the density Richardson’s ground squirrel holes/ha. Eldridge (2004) found a positive but weaker (r = 0.66) correlation between badger and ground squirrel signs of activity. Sargeant and Warner (1972) noticed that their female badger was more active in areas with the densest populations of pocket gophers (Geomys bursarius). Data gathered during spotlighting showed that badgers systematically investigated their hunting grounds, moving back-and-forth or zigzagging in areas occupied by ground squirrels. Although olfaction is believed to play an important role in the search of prey (Lampe 1976), these repetitive movements and the numerous small holes that the badgers dug along the way suggest that they had difficulty in pinpointing the location of hibernating Richardson’s

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ground squirrels. Murie (1992) came to the same conclusion when observing badgers searching for juvenile Columbian ground squirrels (Spermophilus columbianus) in their nest burrows. The difficulty in finding hibernating ground squirrels may explain a change in the diet of the badgers from spring to fall. From April to November, the frequency of ground squirrels in scats decreased from 90 % to 22%. Snead and Hendrickson (1942) found that remains of ground squirrel species occurred in >70% of badger scats in spring and summer, but dropped to < 55% in October-December. They attributed this decrease over fall to the freezing of the ground and a marked reduction in the above ground activity of the ground squirrels. During this time period, badgers’ diet became more diversified and included more mice and cottontails (Sylvilagus spp.). Messick and Hornocker (1981) also found that predation on ground squirrels was higher in spring and early summer. The decrease in importance of ground squirrels in badgers’ scats in the fall suggests that badgers are opportunistic and feed on carrion and on most abundant prey such as voles and mice, and insects. Most of the vegetative material ingested by badgers is probably taken incidentally to the consumption of animals (Svendsen 2003). As previously reported by Sargeant and Warner (1972), the female badger occupied the same den and hardly moved with the onset of winter, this suggesting that little hunting occurred during this time period. While badgers are known to feed on cached ground squirrels in winter (Michener 2000), it is unlikely that they impact significantly on the population of hibernating ground squirrels. Badgers may have a significant impact on ground squirrel populations in spring and summer only. They do not appear to be effective in capturing Richardson’s ground squirrels in fall, and they are not very active in winter when temperatures are below zero. However, this year’s winter was colder than usual, and badgers may be more effective at killing ground squirrels during milder winters. Considering that badgers dig large holes, which cause serious damage to crops, livestock, and farm equipment (Minta and Marsh 1988), their role as a significant control measure must be further investigated.

5.2 LONG-TAILED WEASEL

Long-tailed weasels are known to feed on fossorial rodents. Proulx (2005) showed that long-tailed weasels hunted northern pocket gophers in their burrow systems. Errington (1936) reported that 13-lined ground squirrels (Spermophilus tridemlineatus) bore the brunt of the predation pressure by a weasel family; half of the scats gathered at a latrine had ground squirrel remains. There are no data in the scientific literature on the impact of long-tailed weasel predation on Richardson’s ground squirrels. This study is unique because it demonstrated that weasels could have a significant impact on Richardson’s ground squirrels

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from April to July by killing breeders and young of the year. Our work suggests that predation by weasels could approximate 50% of the juvenile ground squirrel populations, and probably more if one considers that weasels also feed on adults in the spring. In the summer, considering that many popular poisons control 50% of juvenile populations (Proulx et al. 2009), long-tailed weasels may play an important role as a significant control measure. Weasel scats often contained vegetation, sometimes in relatively large volumes. While some of it may have been acquired while feeding on prey, weasels may eat plants for physiological reasons (Silva et al. 2003, Muňoz-Garcia and Williams).

5.3 COYOTE

Coyotes are opportunistic, generalist predators and eat a variety of food items in relation to changes in availability (Bekoff and Gese 2003). Studies have shown pronounced seasonal variation in coyote diets related to the availability of foods (Gipson and Sealander 1976, Litvaitis and Shaw 1980, MacCracken and Hansen 1982, Van Vuren and Thompson 1982, Andelt et al. 1987, Reichel 1991). This study also showed that coyotes had a diversified diet which changed over time. However, this is the first study to investigate coyote food habits in areas where high population densities of Richardson’s ground squirrels have been documented. Our findings suggest that Richardson’s ground squirrels are an important prey of coyotes in southern Saskatchewan as they occurred in >50% of April-July scats. This is in contrast with other studies where ground squirrel remains were found in < 4% of scats (MacCracken 1981,1982; Ortega 1987). As in many studies, voles and mice, ungulates, grass and seeds, and insects were found in coyotes’ scats. Ungulate remains, including those of cattle, usually increase in importance in fall and winter (Bekoff and Gese 2003), and are assumed to have been taken as carrion (Murie 1951, Litvaitis and Shaw 1980, Cepek 2004), although coyotes are known to kill deer in some areas (Voigt and Berg 1987). Vegetation was found in a few scats, presumably from prey stomachs, and the ingestion of grass seeds and leaves (MacCracken 1982). Insects were most important during late summer and fall, as it was also reported by other researchers (Ortega 1987, Reichel 1991). Kuiken et al. (2003) found that grasshoppers were predominant food items when they were unusually abundant in late summer. Of particular interest was the presence of badger remains in summer and fall scats. Coyotes are known to frequent badger grounds, and they have been reported to sometimes associate with badgers to hunt ground squirrels (Minta et al. 1992). However, our findings suggest that coyotes must also feed on young badgers in the summer and on yearlings or adults in the fall. In the latter case, coyotes probably hunt as a group to kill a badger (Rathbun et al.1980).

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6.0 RECOMMENDATIONS

This study showed that all the studied predators, particularly the badger and the long-tailed weasel, fed on Richardson’s ground squirrels during the growing season. More research is required to quantify their impact on ground squirrel populations, and better understand predator-prey relationships on a seasonal basis. In this study, a limited number of badger and coyote scats were analyzed. Badgers are secretive in their defecation habits and frequently deposit scats at the bottom of shallow excavations or bury them in mounds of earth at the entrance to burrows (Snead and Hendrickson 1942, Sargeant and Warner 1972). Coyote scats were difficult to find during summer particularly when farming activities increased in frequency. We recommend that the predator-prey relationships be further investigated by 1) analyzing scats of badgers, weasels and coyotes collected at different times of the year, and 2) monitoring the activities of badgers and long-tailed weasels, and the survival of tagged ground squirrels, in specific areas and at different times of the year. Live-trapping, radio-telemetry, and spotlighting techniques used in 2008 were effective in studying predator-prey relationships and should be used again in future studies.

7.0 ACKNOWLEDGMENTS

We thank the Saskatchewan Ministry of Agriculture (Agriculture Development Fund) for funding this project. We are grateful to Scott Hartley from Saskatchewan Agriculture for facilitating research logistics, and Mike Sherven, Administrator for the Rural Municipality of Mankota, for helping with the identification of study areas. We thank producers Garth Gross, Roland Schafer, Roger Kress, Bruce Switzer, Orin Balas, Craig Knox and Glen Mackenzie for allowing us to conduct this project on their farmlands. We also thank Kenneth Rice from PowerSource Performance Inc. in Edmonton for the maintenance of the equipment.

8.0 LITERATURE CITED Adorjan, A. S., and G. B. Kolenosky. 1969. A manual for the identification of hairs of selected Ontario mammals. Ontario Department of Lands and Forest Research Report (Wildlife) 90. 64 pages. Andelt, W. F., J. G. Kie, F. F. Knowlton, and K. Cardwell. 1987. Variation in coyote diets associated with season and successional changes in vegetation. Journal of Wildlife Management 51: 273-277.

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Bekoff, M., and E. M. Gese. 2003. Coyote, Canis latrans. Pages 467-481 in G. A. Feldhamer, B. C. Thompson, and J. A. Chapman, editors, Wild mammals of North America. Biology, management, and conservation. The Johns Hopkins University Press, Baltimore, Maryland. Bernard, M., G. Michener, and J. Bourne. 2004. Richardson’s ground squirrel pest profile. Unpublished mimeograph, Alberta. 28 pages. Cepek, J. D. 2004. Diet composition of coyotes in the Cuyahoga National Park, Ohio. Ohio Journal of Science 104: 60-64. Chandler, A. C. 1916. A study of the structure of feathers with reference to their taxonomic significance. Zoology (California) 13: 243-266. Eldridge, D. J. 2004. Mounds of the American badger (Taxidea taxus): significant features of North American shrub-steppe ecosystems. Journal of Mammalogy 85: 1060-1067. Errington, P. L. 1936. Food habits of a weasel family. Journal of Mammalogy 17: 406-407. Floyd, T. J., L. D. Mech, and P. A. Jordan. 1978. Relating wolf scat content to prey consumed. Journal of Wildlife Management 42: 528-532. Goodrich, J. M., and S. W. Buskirk. 1998. Spacing and ecology of North American badgers (Taxidea taxus) in a prairie dog (Cynomys leucurus) complex. Journal of Mammalogy 79: 171- 179. Gipson, P. S., and J. A. Sealander. 1976. Changing food habits of wild Canis in Arkansas with emphasis on coyote hybrids and feral dogs. American Midland Naturalist 95: 249-253. Green, J. S., and J. T. Flinders. 1981. Diameter and pH comparisons of coyote and red fox scats. Journal of Wildlife Management 45: 765-767. Jolly, J. N. 1976. Habitat use and movements of the opossum (Trichosurus vulpecula) in a pastoral habitat in Banks Peninsula. Proceedings New Zealand Ecological Society 23: 70-78. Kelly, B. T., and E. O. Garton. 1997. Effects of prey size, meal size, meal composition, and daily frequency of feeding on the recovery of rodent remains from carnivore scats. Canadian Journal of Zoology 75: 1811-1817. Kuiken, T., A. Leighton, and D. Johnson. 2003. Grasshoppers in coyote scats. Blue Jay 61 (1): 51-55. Lampe, R. P. 1976. Aspects of the predatory strategy of the North American badger, Taxidea taxus. PhD Thesis, University of Minnesota, Minneapolis, Minnesota. Lampe, R. P. (1982). Food habits of badgers in east central Minnesota. Journal of Wildlife Management 46: 790-795. Lampe, R. P., and M. A. Sovada. 1981. Seasonal variation in home range of a female badger (Taxidea taxus). The Prairie Naturalist 13: 55-58.

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Murie, A. 1951. Coyote food habits on a southwestern cattle range. Journal of Mammalogy 32: 291-295. Murie, J. O. 1992. Predation by badgers on Columbian ground squirrels. Journal of Mammalogy 73: 385-394. Ortega,J. C. 1987. Coyote food habits in southeastern Arizona. The Southwestern Naturalist 32: 152-155. Powell, R. A. 2000. Animal home ranges and territories and home range estimators. Pages 65- 110 in L. Boitani and T. K. Fuller, editors, Research Techniques in animal ecology. Controversies and consequences. Columbia University Press, New York, New York. Powell, R. A., and G. Proulx. 2003. Trapping and marking terrestrial mammals for research: integrating ethics, standards, techniques, and common sense. Institute of Laboratory Animal Research Journal 44: 259-276. Proulx, G. 1997. A northern pocket gopher (Thomomys talpoides) border control strategy: promising approach. Crop Protection 16: 279-284. Proulx, G. 2005. Long-tailed weasel, Mustela frenata, movements and diggings in alfalfa fields inhabited by northern pocket gophers, Thomomys talpoides. Canadian Field- Naturalist 119: 175-180. Proulx, G., and P. J. Cole. 1998. Identification of northern pocket gopher, Thomomys talpoides, remains in long-tailed weasel, Mustela frenata longicauda, scats. Canadian Field-Naturalist 112: 345-346. Proulx, G, and F. F. Gilbert. 1983. The ecology of the muskrat, Ondatra zibethicus, at Luther Marsh, Ontario. Canadian Field-Naturalist 97: 377-390 Proulx, G., J. A. McDonnell, and F. F. Gilbert. 1987. The effect of water level fluctuations on muskrat, Ondatra zibethicus, predation by mink, Mustela vison. Canadian Field-Naturalist 101: 89-92. Proulx, G., and K. Walsh. 2007. Effectiveness of aluminium phosphide, strychnine, and chlorophacinone to control Richardson’s ground squirrels (Spermophilus richardsonii) in spring, in southern Saskatchewan. Alpha Wildlife Research & Management Ltd. report submitted to Pest Management Regulatory Agency, Ottawa, Ontario. 36 pages. Proulx, G., K. Walsh, N. Mackenzie, and K. Mackenzie. 2009. Assessment of the Effectiveness of Rozol®, Phostoxin®, Strychnine, RoCon®, and various treatments to control Richardson’s Ground Squirrels (Spermophilus richardsonii) in southern Saskatchewan, in spring and

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summer 2008. Alpha Wildlife Research & Management Ltd. report submitted to Saskatchewan Agriculture Development Fund, Regina, Saskatchewan. Ralls, K., and L. L. Eberhardt. 1997. Assessment of abundance of San Joaquin kit foxes by spotlight surveys. Journal of Mammalogy 78: 65-73. Rathbun, A. P., M. C. Wells, and M. Bekoff. 1980. Cooperative predation by coyotes on badgers. Journal of Mammalogy 61: 375-376. Reed, J. E., R. J. Baker, W. B. Ballard, and B. T. Kelly. 2004. Differentiating Mexican gray wolf and coyote scats using DNA analysis. Wildlife Society Bulletin 32: 685-692. Reichel, J. D. 1991. Relationships among coyote food habits, prey populations, and habitat use. Northwest Science 65: 133-137. Ruette, S., P. Stahl, and M. Albaret. 2003. Applying distance-sampling methods to spotlight counts of red foxes. Journal of Applied Ecology 40: 32-43. Sargeant, A. B., and D. W. Warner. 1972. Movements and denning habits of a badger. Journal of Mammalogy 53: 207-210. Siegel, S. 1956. Nonparametric statistics for the behavioral sciences. McGraw-Hill, New York, New York. Silva, S. I., F. M. Jaksic, and F. Bozinovic. 2003. Interplay between metabolic rate and diet quality in the South American fox, Pseudalopex culpaeus. Comparative Biochemistry and Physiology Part A 137: 33–38. Snead, I. E., and G. O. Hendrickson. 1942. Food habits of the badger in Iowa. Journal of Mammalogy 23: 380-391. Svendsen, G. E. 2003. Weasels and black-footed ferret. Pages 650-661 in G. A. Feldhamer, B. C. Thompson, and J. A. Chapman, editors, Wild mammals of North America. Biology, management, and conservation. The John Hopkins University Press, Baltimore, Maryland. Van Vuren, D., and S. E. Thompson, Jr. 1982. Opportunistic feeding by coyotes. Northwest Science 56: 131-135. Voigt, D. R., and W. E. Berg. 1987. Coyote. Pages 345-357 in M. Novak, J. A. Baker, M. E. Obbard, and B. Malloch, editors. Wild furbearer management and conservation in North America. Ontario Ministry of Natural Resources and The Ontario Trappers Association, North Bay, Ontario. Weaver, J. L., and S. W. Hoffman, 1979. Differential detectability of rodents in coyote scats. Journal of Wildlife Management 43: 783-786. Woodroffe, R., F. J. Bourne, D. R. Cox, C. A. Donnelly, G. Gettinby, J. P. McInerney, and W. I. Morrison. 2005. Welfare of badgers (Meles meles) subject to culling:

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patterns of trap-related injury. Animal Welfare 14: 11-17. Zar, J. H. 1999. Biostatistical analysis. Fourth edition. Prentice-Hall, Inc., Upper Saddle River, New Jersey, 663 pages.

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APPENDIX III - THE RICHARDSON’S GROUND SQUIRREL

(SPERMOPHILUS RICHARDSONII) RESEARCH & CONTROL PROGRAM

2009-2010

Report prepared by

Gilbert Proulx, Neil MacKenzie, Keith MacKenzie,

Benjamin Proulx, and Kim Stang

and submitted to

Saskatchewan Association of Rural Municipalities

Regina, Saskatchewan

4 February 2010

65


SUMMARY

In an effort to develop a sustainable, integrated Richardson’s ground squirrel (Spermophilus richardsonii) management program in the Canadian Prairies, this research program aimed to 1) assess and compare, in spring and summer, the control efficacy and selectivity of strychnine, chlorophacinone and aluminum phosphide, 2) investigate the ground squirrel-vegetation height relationship, 3) assess and develop capture-efficient trapping devices, and 4) assess predator-prey relationships in southwest Saskatchewan.

The 2009 toxicant study, when combined with the results of 2007 and 2008 research programs led to the following conclusions:

Phostoxin is effective when it is applied in fields with vegetation and moist soil.

Rozol and Ground Force are effective in grasslands, but less efficient in alfalfa fields, both in spring and summer.

Oat baits treated with freshly produced and freshly mixed 0.4% liquid strychnine (Nu-gro) have the potential to effectively control ground squirrel populations.

Ready-to-use strychnine baits do not have the potential to control at least 70% of ground squirrel populations.

This study showed that the presence of ground squirrels dropped significantly when vegetation reached a minimum height of only 15 cm.

The GT2006 killing trap can be expected to render 70% of captured Richardson’s ground squirrels irreversibly unconscious in 3 minutes (P = 0.05). This trapping device is best suited for the control of ground squirrels in areas where chemical control is not a solution, and for small population concentrations. Multi-capture pen traps with drop-doors mounted on side walls, with strychnine in their centre, were found as effective as strychnine baits placed in burrow openings. No primary poisoning of non-target species and secondary poisoning of predators occurred.

This study showed that badger (Taxidea taxus), long-tailed weasel (Mustela frenata), and red fox (Vulpes vulpes) food habits consisted mainly of ground squirrels in spring and summer,

66


particularly in June-July. Coyotes (Canis latrans) did not appear to be as effective as the other terrestrial predators, but they may still have an impact on ground squirrel populations when they have their pups. Badgers did not establish their home range and hunting grounds at random. Their distribution across landscapes suggested that they associate with larger concentrations of Richardson’s ground squirrels, and therefore aim to maximize their foraging activities.

On the basis of these findings, it is recommended that strychnine baits be further tested with additives and attractants. Tests should include the multi-capture pen trap design in the assessment of its potential to control ground squirrel populations over large areas. Badger multi-scale habitat selection and red fox hunting activities should be further investigated.

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1.0 INTRODUCTION In an effort to develop a sustainable, integrated Richardson’s ground squirrel (Spermophilus richardsonii) management program in the Canadian Prairies, Alpha Wildlife Research & Management Ltd. conducted extensive research on toxicants, predation and grassland characteristics in Saskatchewan, in 2008. Researchers found that, in spring, chlorophacinone (anticoagulant sold as Rozol® and Ground Force®), freshly mixed (FM) 0.4% strychnine-treated oats, and Phostoxin had the potential to control 70% of ground squirrel populations (Proulx et al. 2009a). In summer, however, only FM 0.4% strychnine-treated oats were effective. During both seasons, non-target poisoning was confirmed, particularly in study plots with strychnine-treated baits. Secondary poisoning of predators was confirmed in anticoagulant-treated study plots. Badger (Taxidea taxus) and long-tailed weasels (Mustela frenata) were significant predators of Richardson’s ground squirrels from April to July. Coyote (Canis latrans) food habits were more diversified, and Richardson’s ground squirrel remains were found in 50% of scats in April-July (Proulx et al. 2009b). While toxicants and predators impact on Richardson’s ground squirrel population densities, Proulx and MacKenzie (2009) found that the density of Richardson’s ground squirrel burrow openings decreased significantly when vegetation height was 15 cm. The 2008 research findings suggested that Richardson’s ground squirrel populations may be controlled with the concurrent use of toxicants, predation and vegetation management. However, in order to account for annual variations in environmental conditions and the efficacy of control methods, Alpha Wildlife researchers suggested that studies be repeated in 2009.

2.0 STUDY AREA The study was carried out in southern Saskatchewan, near Hazenmore and Ponteix (Figure 1).


68


3.0 TOXICANTS

3.1 Objectives

1. Assess and compare, in spring and summer, the effectiveness (taking into consideration spring and summer natural mortality) of the following products or methods of application to control Richardson’s ground squirrels:

FM 0.4% strychnine (Nu-Gro Corporation)-treated oats placed in burrow openings in grasslands and alfalfa fields;

FM 0.4% strychnine (Nu-Gro Corporation)-treated alfalfa pellets placed in burrow openings in grasslands;

FM 0.4% strychnine (Nu-Gro Corporation)-treated oats placed in selective pen traps;

FM 0.4% strychnine (Maxim Corporation)-treated oats placed in burrow openings in grasslands;

RTU 0.4% strychnine (Nu-Gro Corporation)-treated oats placed in burrow openings in grasslands;

Rozol® (Nu-Gro Corporation)-treated oats placed in burrow openings in grasslands and alfalfa fields;

Rozol® (Nu-Gro Corporation)-treated oats placed in 17% (1 out of 6 openings) of burrow openings in grasslands;

Rozol® (Nu-Gro Corporation)-treated oats @ ½ concentration placed in burrow openings of grassalnds;

Rozol® (Nu-Gro Corporation)-treated oats @ ½ concentration placed in 17% (1 out of 6 openings) of burrow openings in grasslands;

Ground Force® (Nu-Gro Corporation)-treated winter wheat placed in burrow openings in grasslands and alfalfa fields;

Phostoxin® (Degesch America Inc.) pellets placed in burrow openings in grasslands and alfalfa fields.

69


2. Document the potential impact of these toxicants on non-target species and mammal predators.

3.2 Study Plots

Study plots corresponded to native or seeded grasslands, and pure or mixed alfalfa fields (Table 1) that were located within a same quarter section or in different ones. When located within a same quarter section, study plots were separated by a >150-m-wide buffer zone. In order to capture a similar number of Richardson’s ground squirrels from one study plot to the other, the size of the plots varied from 0.2 to 1.4 ha in spring, and 0.2 to 1.1 ha in summer.

70


Treatment Study plot

Size (ha)

Habitat Pre-treatment Post-treatment Natural

Mortality (%)

Control efficacy (%)

Adult Juvenile

Total Density /ha

Adult Juvenile

Total Density/ha

M F M F Ad.

Ju. M F M F Ad.

Ju.

Ad. Ad & Ju.

Spring(5 May – 1 June)

Rozol® in grasslands

1 1.2 Crested wheat (Agropyron crustatum) and needle-and-thread grass (Hesperostipa comata)

4

13

- - 17 - 14.1 ad.

0

3

- - 3 - 2.5 ad.

- - 75.0

2 0.8 8

12

- - 20 - 25.0 ad.

2

0

- - 2 - 2.5 ad.

- - 85.8

Ground Force® in grasslands

3 0.7 7

13

- - 20 - 28.6 ad.

0

1

- - 1 - 1.4 ad.

- - 92.9

4 0.6 6

14

- - 20 - 33.3 ad.

0

3

- - 3 - 5.0 ad.

- - 78.8

Rozol® in 17% of burrow openings

5 0.4 10

10

- - 20 - 50.0 ad.

2

1

- - 3 - 7.5 ad.

- - 78.8

6 0.4 10

10

- - 20 - 50.0 ad.

2

4

- - 6 - 15.0 ad.

- - 57.5

Table 1. Characteristics of study plots and Richardson’s ground squirrel populations before and after treatment, spring and summer 2009.

71


Rozol® @ half concentration

7 0.5 6

14

- - 20 - 40.0 ad.

1

0

- - 1 - 2.5 ad.

- - 92.9

16 0.5 5

15

- - 20 - 40.0 ad.

0

3

- - 3 - 6.0 ad.

- - 78.8

RTU 0.4% strychnine

9 0.7 3

17

- - 20 - 28.6 ad.

1

4

- - 5 - 7.1 ad.

- - 64.6

33/34

3.5 Crested wheat 10

15

- - 25 - 7.1 ad.

1

6

- - 7 - 2.0 ad.

- - 60.3

Phostoxin® in grasslands (flagged holes)

10/11

1.3 Crested wheat and needle-and-thread grass

11

46

13

19

57 32 43.8 ad.

2

3

0

0

5 0 3.8 ad.

- - 87.6 of adults

92.0 of all animals

Rozol®, half concentration, in 17% of burrow openings

13 0.8 4 14

- - 18 - 22.5 ad.

1

3

- - 4 - 5.0 ad.

- - 68.5

14 0.5 11

10

- - 21 - 42.0 ad.

2

2

- - 4 8.0 ad.

- - 73.0

FM 0.4% Nu-Gro

17 1.1 70% alfalfa (Medicago spp.)

10

12

- - 22 - 20.0 ad.

0

3

- - 3 - 2.7 ad.

- - 80.7

72


strychnine in alfalfa-grass mix

18 0.8 with crested wheat and brome (Bromus spp.)

10

4

- - 14 - 17.5 ad.

2

1

- - 3 - 3.8 ad.

- - 69.6

Phostoxin® in alfalfa-grass mix (non-flagged holes)

19/20/21

5.4 18

14

2 2 32 4 5.9 ad.

6

4

0 0 10 0 1.9 ad.

- - 55.7 of adults

60.6 of all animals

Rozol® in pure alfalfa

23 0.6 Alfalfa 6 15

- - 21 - 35.0 ad.

3

3

- - 6 - 10.0 ad.

- - 59.5

24 0.8 7 10

- - 17 - 21.2 ad.

1

3

- - 4 - 5.0 ad.

- - 66.7

Ground Force® in pure alfalfa

25 0.6 Alfalfa 5 9

- - 14 - 23.3 ad.

2

2

- - 4 - 6.7 ad.

- - 59.5

26 0.6 8 9

- - 17 - 28.3 ad.

1

2

- - 3 - 5.0 ad.

- - 75.0

FM 0.4% Nu-Gro strychnine in grassland

27 2.2 Crested wheat 5 15

- - 20 - 9.1 ad.

0

2

- - 2 - 0.9 ad.

- - 85.8

28 0.9 11

9

- - 20 - 22.2 ad.

1

3

- - 4 - 4.4 ad.

- - 71.7

73


FM 0.4% Nu-Gro strychnine-treated alfalfa pellets in grassland

29 1.8 16

5

- - 21 - 11.7 ad.

5

0

- - 5 - 2.8 ad.

- - 66.3

30 0.8 9

12

- - 21 - 26.3 ad.

2

7

- - 9 - 11.3 ad.

- - 60.7


Size (ha)

Habitat Pre-treatment Density /ha

Post-treatment Density/ha

Natural

Mortality (%)


Table 1 – Cont’d.

74


Adult Juvenile

Total Adult Juvenile

Total Ad. Ad & Ju.

M F M F Ad.

Ju. M F M F Ad.

Ju.

FM 0.4% Maxim strychnine in grassland

31 0.9 12

8

- - 20 - 22.2 ad.

5

1

- - 6 - 6.7 ad.

- - 57.5

32 1.2 8

12

- - 20 - 16.7 ad.

2

4

- - 6 - 5.0 ad.

- - 57.5

Control (no-treatment)

8 0.7 Crested wheat and needle-and-thread grass

4 18

10

9

22 19 31.4 ad.

2

9

4 6 11 10

15.8 ad.

50.0 51.2 -

12 0.7 70% alfalfa with crested wheat and brome

14

8

5

3

22 8 31.4 ad.

10

8

3 3 18 6

25.7 ad.

18.2 20.0 -

22 0.7 Crested wheat and needle-and-thread grass

7

13

7

5

20 12 28.6 ad.

6

10

4 3 16 7

22.9 ad.

20.0 28.1 -

Summer (14 June – 2 July)


19 0.3 Crested wheat - - 10

10

- 20 66.7 ju.

- - 1 1 - 2

6.7 ju.

- - 86.1

22 0.4 - - 1 - 20 50.0 - - 2 0 - 5.0 - - 86.1

75


1 9 ju. 2 ju.


21 0.4 - - 14

6

- 20 50.0 ju.

- - 0 0 - 0

0.0 ju.

- - 100.0

24 0.6 - - 10

11

- 21 35.0 ju.

- - 1 0 - 1

1.7 ju.

- - 93.4


14 0.3 Dry, rocky, native grassland

- - 10

11

- 21 70.0 ju.

- - 1 4 - 5

16.7ju.

- - 66.9

16 0.6 - - 12

8

- 20 33.3 ju.

- - 2 1 - 3

5.0 ju.

- - 79.1


13 0.4 - - 11

9

- 20 50.0 ju.

- - 4 2 - 6

15.0 ju.

- - 58.3

15 0.3 - - 12

8

- 20 66.7 ju.

- - 2 4 - 6

20.0 ju.

- - 58.3

RTU 0.4% strychnine


14

- 21 70.0 ju.

- - 4 7 - 11

36.7 ju.

- - 27.1

7 0.4 Open grassland with crested wheat and native grasses

- - 11

10

- 21 52.5 ju.

- - 2 5 - 7

17.5 ju.

- - 53.6

Phostoxin® in grasslands (flagged


13

- 27 15.9 ju.

- - 6 2 - 8

4.7 ju.

- - 58.8

76


holes)



19

- 23 38.3 ju.

- - 0 7 - 7

11.7 ju.

- - 57.7

23 0.7 - - 12

9

- 21 30.0 ju.

- - 3 2 - 5

7.1 ju.

- - 66.9


Size (ha)

Habitat Pre-treatment Post-treatment Natural

Mortality (%)


Adult Juvenile

Total Density juveniles/ha

Adult Juvenile

Total Density/ha

M F M F Ad.

Ju. M F M F Ad.

Ju.

Ad. Ad. & ju.

77


0.4% Nu-Gro strychnine in alfalfa-grass mix

5 0.3 60% alfalfa with crested wheat

- - 8

12

- 20 66.7 ju.

- - 3

3

- 6

20.0 ju.

- - 58.3

8 0.7 - - 11

10

- 21 30.0 ju.

- - 3

3

- 6

8.6 ju.

- - 60.2

Phostoxin® in alfalfa-grass mix (flagged holes)

9 0.6 - - 7

16

- 23 38.3 ju.

- - 0

3

- 3

5.0 ju.

- - 81.9

Rozol® in alfalfa


- - 8

13

- 21 70.0 ju.

- - 0

1

- 1

3.3 ju.

- - 93.4

11 0.4 90% alfalfa - - 10

8

- 18 45.0 ju.

- - 1

4

- 5

12.5 ju.

- - 61.4

Ground Force® in alfalfa


- - 11

10

- 21 52.5 ju.

- - 1

0

- 1

3.3 ju.

- - 93.4

12 0.3 90% alfalfa - - 12

10

- 22 73.3 ju.

- - 7

0

- 7

23.3 ju.

- - 55.7

0.4% Nu-Gro strychnine in grassland


9

- 22 73.3 ju.

- - 4

2

- 6

20.0 ju.

- - 62.1

28 0.5 - - 8

12

- 20 40.0 ju.

- - 2

4

- 6

12.0 ju.

- - 58.3

78



1 0.6 Open grassland with crested wheat and native grasses

- - 13

8

- 21 35.0 ju.

- - 7

2

- 9

15.0 ju.

- - 40.4

6 0.3 - - 12

10

- 22 73.3 ju.

- - 5

2

- 7

23.3 ju.

- - 55.7



11

- 20 66.7 ju.

- - 3

3

- 6

20.0 ju.

- - 58.3

26 0.2 - - 9

11

- 20 100.0 ju.

- - 2

5

- 7

35.0 ju.

- - 51.3

Control (no-treatment)

10 0.4 60% alfalfa with crested wheat and brome

- - 12

8

- 20 50.0 ju.

- - 8

6

- 14

35.0 ju.

- 30.0 -


14

- 23 115.0 ju.

- - 8

9

- 17

85.0 ju.

- 26.1 -

FM 0.4% strychnine(Nu-Gro Corporation)-treated oats placed in selective pen traps

29 0.1 - - 6

6

- 12 120.0 ju.

- - 4 cap

3 cap

- 7 cap

- - - 58.3

30 0.1 - - 6

8

- 14 140.0 ju.

- - 4 cap

3 ca

- 7 ca

- - -* 50.0

79


M = male; F = female; Ad. = adult; ju. = juvenile; cap = captured.

*No natural mortality.

p p

Table 1 – Cont’d.

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3.3 Methods

Live-trapping was conducted in spring (5 May-1 June) and summer (14 June-2 July) using 15 x 15 x 48 cm Tomahawk (Tomahawk Live Trap, Tomahawk, Wisconsin) live-traps baited with peanut butter on bread. Traps were set early in the morning and checked by mid-afternoon. All ground squirrels were tagged (Monel # 1 tag, Newport, Kentucky, USA) in both ears. Their sex, weight, and general body condition were recorded before releasing them at their capture site. In spring, captured populations consisted of adult Richardson’s ground squirrels in most study plots; in Phostoxin® plots, both adults and juveniles made up the populations. In summer, only juveniles were included in the populations. Live-trapping followed the highest standards of humaneness (Powell and Proulx 2003).

The exact size of study plots was determined on the basis of capture locations. Toxicants were applied at burrow systems where captures and recaptures occurred, and in all the holes with signs of activity located within the delineated study plots. The efficacy of Phostoxin® was tested in fields where burrow holes had been flagged the day before treatment, and in fields where burrow holes were not flagged. Particular attention was paid to the identification of burrow systems that may be inhabited by carnivores, and particularly species at risk such as the swift fox (Vulpes velox) and the burrowing owl (Athene cunicularia). Burrows with fresh signs of badger (Taxidea taxus) and long-tailed weasels (Mustela frenata) were not treated with toxicants.

Phostoxin aluminum phosphide tablets were deposited in Richardson’s ground squirrel holes in spring and summer. The application occurred in the morning, before sunrise. All burrow systems were filled with dirt immediately after treatment. In spring, because vegetation was short (< 10 cm) in both the grassland and the alfalfa-grass mix study plots, burrow openings were flagged in the grassland only because of the high density of animals and burrow systems. However, because spring results suggested that not flagging burrow openings may result in lower control efficacy, all study plots were flagged during the summer tests.

Early in the morning, one tablespoon of strychnine bait (approximately 13-15 g; FM and RTU) was placed with a long-handled spoon as far as possible into burrow openings. As per label instructions, the treated holes were covered with dirt. Rozol was used at standard (i.e., 0.7% chlorophacinone mixed with hulless oats at a weight by weight ratio of 1:13), or half concentration, in all burrow openings or in 17% of openings, as specified in different test protocols. Ground Force (ready-to-use 0.005% chlorophacinone-treated, green-colored, winter wheat grains; Nu-Gro Corporation, Brantford, Ontario) was deposited in all burrow

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entrances. All anticoagulant baits were placed in burrow openings early in the morning. A second treatment of burrow openings occurred 48 hours later. No oats were deposited in burrow openings in control study plots5.

3.4 Assessment of the control efficacy of toxicants

In each study plot, live trapping was initiated the day following the last treatment, and lasted up to 15 days to capture all animals present. An attempt was made to recover carcasses of ground squirrels and non-target species that died on surface. Dead animals were collected and identified to species; a few carcasses were autopsied to confirm the presence of baits in their cheeks and digestive system. All collected carcasses were buried in a 60 cm-deep dirt hole. When moribund animals were found, they were quickly and humanely dispatched with a blow to the head.

The control efficacy of toxicants was evaluated using the Abbott’s formula modified by Henderson and Tilton (1955) as follows6:

M = 100 x [1 – (t2 x c1)/(t1 x c2)]

Where M (%) = Richardson’s ground squirrel mortality, t = treated population, c = control population, 1 = population before treatment, and 2 = population after treatment.

5 In 2008, non-treated oats had been deposited in burrow openings and covered with dirt in control study plots. In the following days, all holes had been re-opened, and no death was incurred by the treatment. This procedure was not repeated in 2009 to save time and material.

6 In the past, control efficacy was calculated by subtracting the average natural mortality of populations from that of poison-treated populations (Proulx and Walsh 2007). In this study, in order to be found acceptable, a toxicant had to control 70% of the ground squirrels of a population. However, if the natural mortality exceeds 30%, a toxicant cannot pass the acceptable criterion unless it kills all animals that survived natural mortality. In order to calculate the true effectiveness of toxicants, control efficacy must be calculated on the number of animals surviving natural mortality. Therefore, one must assume that all the natural mortality has occurred prior treatment with toxicants. The Abbott’s formula modified by Henderson and Tilton (1955) does this. This is certainly true for acute poisons and gases. In the case of anticoagulants, however, poisoned animals forage on surface up to 1 week before succumbing to the poison. Predation may occur on the first day of poisoning when the animals’ health is not compromised. Later, predators feed on moribund animals, but the health of these animals had already been compromised by the anticoagulant, which is the real reason for the animals’ deaths. Even if the supposition that natural mortality occurred before treatment with anticoagulants may not always be true, it is a necessary assumption to compare the impact of diverse toxicants on Richardson’s ground squirrel populations.

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3.5 Performance criterion

The control efficacy of each toxicant was evaluated in 2 study plots. A toxicant was found acceptable if, in both study plots, it controlled at least 70% of ground squirrel populations (Matschke and Fagerstone 1984, Proulx 2002). The 70% minimum acceptation level was also used when comparing the performance of toxicants over the years.

3.6 Statistical analyses

Because there may be a marked variation in bait rejection from one study plot to the other (Proulx and Walsh 2007, Proulx et al. 2009a), and in order to take into account the possible variation in the behavior of animals from different populations, results from similar treatments were not pooled together for statistical analysis. The Fisher Exact Probability test and Chi-square statistics (Siegel 1956) were used to compare the efficacy of baits among them (Witmer et al. 1995, Proulx 1998, Ramey et al. 2002, Arjo and Nolte 2004). Analysis of variance (ANOVA) and Tukey tests were used to compare mean control levels of toxicants (Zar 1999). A 0.05 level of significance was used for all tests.

3.7 Results

3.7.1 Spring (5 May-1 June)

3.7.1.1 Pre-treatment Population Characteristics

Captured ground squirrel populations ranged from 14 to 25 adults in most study plots in spring (5 May-1 June). Phostoxin tests were conducted in larger study plots, and populations ranged from 36 to 89 animals (adults and juveniles) (Table 1). Population densities ranged from 5.9 to 50 adults/ha (Table 1).

3.7.1.2 Control Efficacy

Adult natural mortality ranged from 18.2 to 50% in control plots, and averaged 29.4%. The whole population (adult and juvenile) natural mortality ranged from 20 to 51.2%, and averaged 33.1% (Table 1).

In study plots treated with poison baits, between 1 and 10 animals were re-captured after treatment with toxicants, and population densities ranged from 1.4 to 15 adults/ha (Table 1).

Control levels ranged from 57.5 to 92.9% (Table 1). The following toxicants controlled

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70% of ground squirrel populations in both study plots where they were applied: Rozol® in grasslands, Ground Force® in grasslands, and Rozol® at half concentration in grasslands. FM 0.4 % Nu-gro strychnine-treated oats in grasslands almost passed in mixed alfalfa-grass study plots with control levels of 80.7% and 69.6% (Table 1).

Phostoxin controlled more than 70% of ground squirrels in a grassland where all the holes had been flagged before treatment: it controlled 87.6 of the adults, and 92% of the adult-juvenile population (Table 1). In the mixed alfalfa-grass study plot where holes had not been flagged prior to treatment, it controlled only 55.7% of the adults and 60.6% of the whole marked population (Table 1).

There were not significant differences (P > 0.05) between control efficacy levels of most toxicants. However, toxicants with control efficacy levels >79% were significantly (P < 0.05) more effective than those with control efficacy levels 66.7%.

3.7.1.3. Richardson’s Ground Squirrels Found Dead on Surface

Dead or dying ground squirrels were found on surface of most study plots (Table 2).

3.7.1.4 Non-target and Secondary Poisoning

Non-target poisoning was confirmed in 5 study plots treated with strychnine baits, and in 1 study plot treated with Rozol (Table 2).

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Table 2. Non-target and secondary poisoning in spring and summer toxicant tests.


Richardson’s ground squirrels found dead or dying on surface

Non-target/secondary poisoning

SPRING

Rozol® in grasslands 1 12

2 66

Ground Force® in grasslands 3 18

4 34


5 11

6 8

Rozol® @ half concentration 7 19

16 5

RTU 0.4% strychnine 9 9 1 western meadowlark (Sturnella neglecta)

33/34 0


10/11 58


13 5 1 deer mouse (Peromyscus maniculatus)

14 1

FM 0.4% Nu-Gro strychnine in alfalfa mix

17 15 7 deer mouse, 1 northern harrier (Circus cyaneus),

1 Vesper sparrow (Pooecetes gramineus)

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18 0 1 deer mouse

Phostoxin® in alfalfa mix (non-flagged holes)

19/20/21 0

Rozol® in pure alfalfa 23 17

24 7

Ground Force® in pure alfalfa 25 1

26 14

FM 0.4% Nu-Gro strychnine in grassland

27 5

28 11 1 Vesper sparrow


29 1

30 2


31 2 1 meadowlark

32 1

SUMMER

Rozol® in grasslands 19 0

22 1

Ground Force® in grasslands 21 3

24 1


14 1

16 3

Rozol® @ half concentration 13 3 1 deer mouse

15 0

86


RTU 0.4% strychnine 2 1 4 deer mouse

7 0


20 0


18 1

23 0

0.4% Nu-Gro strychnine in alfalfa mix

5 0

8 2

Phostoxin® in alfalfa mix (flagged holes)

9 1

Rozol® in alfalfa 4 2

11 1 1 long-tailed weasel

Ground Force® in alfalfa 3 7 3 long-tailed weasels

12 0

0.4% Nu-Gro strychnine in grassland

27 1 2 deer mouse

28 7 4 deer mouse, 1 horned lark (Eremophila alpestris)


1 0

6 0


25 4 1 deer mouse

26 1

FM 0.4% strychnine(Nu-Gro Corporation)-treated oats placed in selective pen traps

29 0

30 0

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3.7.2 Summer (14 June - 2 July)

3.7.2.1 Pre-treatment Population Characteristics

Captured ground squirrel populations ranged from 20 to 27 juveniles in all study plots (Table 1). Population densities ranged from 15.9 to 140 juveniles/ha (Table 1).

3.7.2.2 Control Efficacy

Juvenile natural mortality was 30% and 26.1% in 2 control plots, and averaged 28.1% (Table 1).

In study plots treated with poison baits, between 0 and 11 animals were re-captured after treatment with toxicants, and population densities ranged from 0 to 23.3 juveniles/ha (Table 1). Control levels ranged from 40.4% to 100% (Table 1). The following toxicants controlled

70% of ground squirrels in both study plots where they were applied: Rozol® and Ground Force® in grasslands (Table 1). Phostoxin controlled more than 70% of the ground squirrels in mixed alfalfa-grass study plots where vegetation was >30 cm high. However, in a grass study plot with < 10 cm vegetation and very dry soil conditions, it controlled only 58.8% of the animals (Table 1).

There were not significant differences (P > 0.05) between control efficacy levels of toxicants that controlled 66.9% of the populations. Phostoxin in the mixed alfalfa-grass study plots and anticoagulants had control levels that were significantly higher (P < 0.05) than toxicants that did not meet the 70% acceptation level.

3.7.2.3. Richardson’s Ground Squirrels Found Dead on Surface

Dead or dying ground squirrels were found on surface of most toxicants (Table 2).

3.7.2.4 Non-target and Secondary Poisoning

Non-target poisoning was confirmed in 4 study plots treated with strychnine baits, and in 3 study plots treated with anticoagulants (Table 2). Secondary poisoning was confirmed only in fields treated with Rozol® in grasslands and Ground Force®. Autopsies of poisoned long-tailed weasels confirmed internal bleeding. Blood was also seeping from foot pads and gums.

3.7.3 Synthesis of 2007-2009 results

The ability of toxicants to control Richardson’s ground squirrel populations over the years is presented in Table 3.

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Treatment

Season Years

2007 2008 2009

Study plot

nos.

Control

level (%)

Study plot nos.

Control

level (%)

Study plot

nos.

Control

level (%)

Phostoxin®

Spring 5 (high vegetation, moist soil)

7 (low vegetation, dry soil)

71.4

36.0

23 (low vegetation, moist soil)

25 (low vegetation, moist soil)

78.5

85.1

10/11 (low vegetation, moist soil)

19-21 (low vegetation, moist soil, unflagged burrowsl)

87.6 (adults)/

92 (adults + juveniles)

55.7 (adults)/

60.6 (adults + juveniles)

Summer

- - - - 9 (high vegetation, moist soil)

81.9

89


20 (low vegetation, dry soil)

58.8


Spring - - 8

9

100

89.2

1

2

75.0

85.8

Summer

- - 5 67.2 19

22

86.1

86.1

Rozol®+ in grasslands

Spring - - 10

11

100

100

- -

Summer

- - 3 75.4 - -

Rozol® in alfalfa (pure or mixed)

Spring 3

4

49.7

63.0

- - 23

24

59.5

66.7

Summer

- - 25 50.8 4

11

93.4

61.4

Rozol®+ in Spring - - - - - -

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Table 3. Multi-year performance of toxicants for Richardson’s ground squirrels Proulx and Wash 2007, Proulx et al. 2009a, and this study.

alfalfa (pure or mixed)

Summer

- - 26 40.3 - -

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Table 3. Cont’d

Treatment Season Years

2007 2008 2009

Study plots

Control

level (%)

Study plots

Control

level (%)

Study plots Control

level (%)


Spring - - - - 5

6

78.8

57.5

Summer - - - - 14

16

66.9

79.1


Spring - - - - 7

16

92.9

78.8

Summer - - - - 13

15

58.3

58.3

Rozol®, half Spring - - - - 13 68.5

92


concentration, in 17% of burrow openings

14 73.0

Summer - - - - 18

23

57.7

66.9

Rozol®+ in burrow openings and in perimeter bait stations

Spring - - 5

6

100

100

- -

Summer - - 11

15

50.8

50.8

- -

Rozol®+ in bait stations

Spring - - 19

20

73.1

85.7

- -

Summer - - 13

19

62.7

76.6

- -


Spring - - 7

21

95.1

71.9

3

4

92.9

78.8

Summer - - 9 67.2 21

24

100

93.4

Ground Spring - - - - 25 59.5

93


Force® in alfalfa (pure or mixed)

26 75.0

Summer - - 10 67.2 3

12

93.4

55.7

FM 0.4% Nu-Gro strychnine with oats in grassland

Spring 6

8

38.1

38.1

3

4

73.1

95.4

27

28

85.8

71.7

Summer - - 4

6

75.4

75.4

27

28

62.1

58.3

Table 3. Cont’d.

Treatment Season Years

2007 2008 2009

Study plots Control

level (%)

Study plots

Control

level (%)

Study plots Control

level (%)

FM 0.4% Nu-Gro strychnine

Spring - - - - 17

18

80.7

69.6

94


with oats in alfalfa mix

Summer - - - - 5

8

58.3

60.2

FM 0.4% Nu-Gro strychnine with canary seeds in grassland

Spring - -

14

16

84.5

63.9

- -

Summer - - 1

2

83.4

92.2

- -


Spring - - - - 29

30

66.3

60.7

Summer - - - - 1

6

40.4

55.7

FM 0.2% Nu-Gro strychnine with oats in grassland

Spring - - 13

15

52.3

48.4

- -

Summer - - 12

16

59.0

65.8

- -

FM 0.4% Spring - - - - 31 57.5

95


Maxim strychnine in grassland

32 57.5

Summer - - - - 25

26

58.3

51.3

RTU 0.4% strychnine in grasslands

Spring 9

10

33.3

59.7

12

18

53.6

47.6

9

33/34

64.6

60.3

Summer - - 7

8

26.2

18.0

2

7

27.1

53.6

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Phostoxin was found effective throughout the years when it was applied in fields with vegetation and moist soil (Table 3). Under dry soil conditions, however, its control efficacy dropped below 70%. Rozol (including Rozol+ which has the same concentration of chlorophacinone as the original product but is different due to the addition of a non-lethal attractant) and Ground Force were effective in grasslands, but failed consistently in alfalfa fields, both in spring and summer. In 2009, they controlled >70% of ground squirrels in one alfalfa field when plants suffered from an extended drought period and were dying. The use of bait stations with Rozol was tested in 2008 only, and results indicated that, in spring, this method was as effective as depositing poison baits in burrow openings. The efficacy of FM Nu-gro strychnine varied significantly from 2007 (a 2002 formula), to 2008 (produced the same year), and to 2009 (1-year-old solution). Maxim strychnine baits were ineffective in spring and summer 2009. During 3 consecutive years, RTU strychnine failed to control at least 70% of ground squirrel populations. On the basis of 3 years of research, the following datasets may be compared to each other (Table 4):

Phostoxin in fields with vegetation and moist soils where the burrow openings have been flagged prior to treatment, spring and summer.

Rozol and Rozol+ in grasslands, spring and summer.

Rozol and Rozol+ in alfalfa (pure or mixed), spring and summer.

Ground Force in grasslands, spring and summer.

Ground Force in alfalfa (pure and mixed), spring and summer.

FM Nu-gro 0.4% strychnine, spring and summer 2008.

FM Nu-gro 0.4% strychnine, spring and summer 20097.

FM 0.4% Maxim strychnine, spring and summer 2009.

RTU 0.4% strychnine, spring 2007, spring and summer 2008 and 2009.

There was a significant difference (F8,52 = 8.612, P < 0.001) between average control levels of different toxicants. Rozol and Ground Force in grasslands, Phostoxin, FM Nu-gro 7 The 2007 data were not considered due to the old age of the strychnine solution.

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0.4% strychnine 2008, and Ground Force in alfalfa had control levels that were significantly higher (P < 0.05) than those of other toxicants (Figure 2). The average control level of FM Nu-gro 0.4% strychnine 2009 was borderline; it was not different (P > 0.05) from the average control levels of these high performing toxicants, but it was also similar (P> 0.05) to that of toxicants with less performance (Figure 2). RTU 0.4% strychnine had a control level similar (P > 0.05) to that of Rozol in alfalfa and FM 0.4% Maxim strychnine, but lower than that of all other poisons (Table 4, Figure 2). While yearly data suggested that anticoagulants do not perform well in alfalfa fields, 2 years of research showed that, on average, Ground Force met the 70% acceptation criterion.

Table 4. Average control level (%) obtained with different toxicants from 2007 to 2009.

Toxicant (n) Average control level (%)

Standard deviation (%)

Phostoxin (5) 80.9 6.3

Rozol in grasslands (10) 86.5 11.5

Rozol in alfalfa (8) 60.6 15.8

Ground Force in grasslands (7) 85.6 12.8

Ground Force in alfalfa (5) 70.2 15.0

FM Nu-gro strychnine 2008 (4) 79.8 10.4

FM Nu-gro strychnine 2009 (8) 68.3 10.5

FM Maxim strychnine (4) 56.2 3.3

RTU strychnine (10) 44.4 16.8

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Figure 2. Comparison of the efficacy of various toxicants to control Richardson’s ground squirrels. Treatments within a same group had similar (P > 0.05) mean control levels.

4.0 GROUND SQUIRREL -VEGETATION HEIGHT RELATIONSHIP

4.1 Objective

Determine the relationship existing between Richardson’s ground squirrel distribution and vegetation height.

4.2 Study Plots

Study plots corresponded to native grasslands used as pastures on short rotational basis (Aneroid), or crested wheat-dominated fields that had not been grazed for at least 2 years

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(Ponteix, Hazenmore, and Cadillac). In all regions except Cadillac, study plots with vegetation of different heights were adjacent to each other, within a same quarter section. In Cadillac, plots were not adjacent to each other due to the interspersion of tilled fields and annual crops, but they were < 2 km apart.

4.3 Methods

Field investigations of Richardson’s ground squirrel abundance in fields with different vegetation heights were carried out from 5 to 20 May. Vegetation was classified according to 3 heights: 1) Low, < 10-cm high; 2) Medium, 15-20-cm high; and 3) Tall, 30-cm high. Three 0.49 ha study plots, located >10 m from the border of fields and 10-m-equidistant from each other, were located in each study plot. Ground squirrel burrow openings were inventoried in each study plot by 5 people walking up and down fields, 5-m abreast. Because ground squirrel infestation levels vary among regions, the comparison of burrow opening abundance between fields of different vegetation heights was done at the regional level. However, because there was a marked trend in the abundance of burrow openings according to vegetation heights, data analyses were also carried out on pooled data. Analysis of variance (ANOVA), Tukey tests, and Student-t tests, were used to compare mean numbers of burrow openings/quadrat (Zar 1999).

4.3 Results

4.3.1 Ponteix

Three fields with different vegetation heights were found adjacent to each other. There was a significant difference (F2,6 = 12.8, P < 0.01) in the number of Richardson’s ground squirrel burrow openings/quadrat (Table 5). The average number of burrow openings/quadrat was significantly higher (P < 0.05) in short vegetation than in medium and high vegetation. There was no significant difference (P > 0.05) in the mean number of burrow openings/quadrat in medium and high vegetation types.

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Table 5. Number of Richardson’s ground squirrel burrow openings/0.49 quadrat in fields with short

(< 10-cm high), medium (15-20-cm high), and high (> 30-cm high) vegetation, May 2009.

Region Mean number of burrow openings/0.49 ha quadrat (standard deviation) *

Short vegetation Medium vegetation Tall vegetation

Ponteix 395.0 (109.1) 173.0 (61.7) 109.0 (12.1)

Aneroid 197.7 (72) 53.7 (24.9) -

Hazenmore 252.0 (28.6) - 169.7 (38.2)

Cadillac 124.7 (78) 2.0 (2) 2.3 (4)

Pooled data

n 12 9 9

Mean 242.3 76.2 93.7

Standard deviation 122.7 82.9 76.1

* n = 3 quadrats/vegetation type/region.

4.3.2 Aneroid

Two fields with short and medium vegetation heights were found adjacent to each other. There was a significant difference (t = 3.318, P < 0.05) in the number of Richardson’s ground squirrel burrow openings/quadrat (Table 5). The average number of burrow openings/quadrat was significantly higher in short than in medium vegetation.

4.3.3 Hazenmore

Two fields with short and tall vegetation heights were found adjacent to each other. There was a significant difference (t = 2.991, P < 0.05) in the number of Richardson’s

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ground squirrel burrow openings/quadrat (Table 5). The average number of burrow openings/quadrat was significantly higher in short than in tall vegetation.

4.3.4 Cadillac

Three fields with different vegetation heights were found nearby each other. There was a significant difference (F2,6 = 7.378, P < 0.05) in the number of Richardson’s ground squirrel burrow openings/quadrat (Table 5). The average number of burrow openings/quadrat was significantly higher (P < 0.05) in short vegetation than in medium and high vegetation. There was no significant difference (P > 0.05) between medium and high vegetation types.

4.3.5 Pooled data

There was a significant difference (F2,27 = 9.237, P < 0.005) in the number of Richardson’s ground squirrel burrow openings/quadrat in different vegetation heights (Table 5). The average number of burrow openings/quadrat was significantly higher (P < 0.05) in short vegetation than in medium and high vegetation. There was no significant difference (P > 0.05) between medium and high vegetation types.

5.0 ASSESSMENT & DEVELOPMENT OF CAPTURE-EFFICIENT

TRAPPING DEVICES

5.1 Objective

Assess and compare the capture efficiency of various live and kill trapping devices.

5.2 Study Plots

All traps were tested in grasslands in Hazenmore and Ponteix.

5.3 Methods

Two trap models were tested and/or developed:

1. GT2006 (Lee’s Trapworks Ltd., Swift Current, Saskatchewan): guillotine-type killing trap set individually at burrow openings (Figure 3). When a ground squirrel leaves its burrow system, it must walk through an opening and push on a fork trigger that releases a metal plate that strikes the animal dorsally.

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Figure 3. The GT2006 trap.

2. Multi-capture pen trap (Alpha Wildlife, Sherwood Park, Alberta): 90 cm x 90 cm wire-mesh box trap with at least 2 one-way door entrances. (Figure 4).

Figure 4. The pen trap.

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Four types of doors (Figure 5) were tested:

Drop-door in a PVC pipe: the animal pushes the door open, and the door closes back on its own once the animal has cleared the entrance.

Treadle door in a PVC pipe: the treadle is heavier on one side and, once the animal has walked over it to enter the trap, it falls back in place and blocks the entrance from the inside of the trap.

Drop-door with locking treadle: the animal pushes the door open (which falls back on its own) to enter the trap. If the animal comes back towards the door, a treadle that is heavier on one side pops up and locks the drop-door in place.

Drop-door mounted on the side of the pen trap.

Figure 5. Door models (not at scale) tested with the multi-capture pen trap: a) drop-door in PVC pipe; b) treadle door in PVC pipe; c) drop-door and treadle lock in PVC pipe; and d) drop-door on the side of the pen trap.

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The GT2006 trap was tested for its humaneness from 28 June to 6 July. Six taps were repeatedly used for the capture of 9 animals (3 of them were re-used for the capture of a second animal, for a total of 9 captures). One trap was set immediately after a ground squirrel sought refuge in its burrow system. Five more traps were set in neighboring burrow holes that may be connected to the original burrow system. Upon firing of the trap, the researcher started a chronometer, and determined time to loss of consciousness by monitoring the corneal and palpebral reflexes (Proulx et al. 1989). The GT2006 trap was considered humane if it rendered 9 out of 9 ground squirrels irreversibly unconscious in 3 min. In the event of an animal not losing consciousness within this time period, it would be euthanized with a sharp blow to the head. On the basis of a one-tailed binomial test (Zar 1999), the GT2006 trap would be expected, at a 95% level of confidence, to humanely kill 70% of all Richardson’s ground squirrels captured on traplines (Proulx et al. 1993). This humane standard, developed by Proulx and Barrett (1989), is the best-defined, objective and published criterion consistent with state-of-the art technological development (Powell and Proulx 2003). Time to loss of heartbeat was determined with a stethoscope. Injuries caused by the trap were determined in the field through examination of the carcass. The assessment of the capture efficiency of the GT2006 was limited to observations made during the testing of the humaneness of the trap.

The pen trap was tested for its capture-efficiency. A preliminary assessment of door types consisted in field observations only. Once a door model was judged effective, 2 prototypes of the pen trap were used to assess their efficacy to control Richardson’s ground squirrels with strychnine baits. In two 0.1-ha study plots, ground squirrels were captured in Tomahawk traps and tagged as per Section 3.3. A container with FM 0.4% strychnine-treated oats was placed at the centre of each pen trap. Peanut butter was used as attractant. The traps were set from 29 June to 5 July. The number and identity of captured animals were recorded daily. The Fisher Exact Probability test (Siegel 1956) was used to compare the efficacy of pen taps with strychnine to treatments with FM 0.4% Nu-gro strychnine baits, FM 0.4% Maxim strychnine baits, and RTU 0.4% strychnine baits. A 0.05 level of significance was used for all tests.

5.4 Results

5.4.1 GT2006

Nine of 9 juveniles (3 males, 4 females, 2 unknown; 300-470 g) were successfully killed (Table 6). The average time to loss of consciousness and heartbeat were < 40.1 (standard deviation: 49.2) seconds and 125 ( 55.2) seconds, respectively (Table 6). In 7

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cases, the animals were struck on the head, and the skull was fractured. In 2 cases, the strike occurred at the skull-neck junction, and the animals died of asphyxiation. This study showed that the GT2006 trap can be expected to render 70% of captured Richardson’s ground squirrels irreversibly unconscious in 3 minutes (P = 0.05).

Table 6. Location of strike, time intervals between trap firing and irreversible loss of corneal and palpebral reflexes and heartbeat of 9 juvenile Richardson’s ground squirrels in kill tests with the GT2006 trap, Hazenmore, summer 2009.

Location of strike Time of loss after trap firing (sec)

Behind or across the ears

Across the eyes Junction of skull and neck

Eye reflexes Heartbeat

6 1 2 10* - 132 48-232

*Animal was unconscious on arrival of researcher.

Time to capture ranged from 5 to 30 minutes, and the targeted animal was not always captured in the burrow opening where it had sought refuge. In 4 out of 9 tests, only 1 animal was captured. In 2 other tests, 2 and 3 animals were captured at the same time in different traps.

5.4.2 Multi-capture (pen) tap

5.4.2.1 Drop-door in PVC pipe

One pen trap set for 2 days in early April captured 7 Richardson’s ground squirrels. However, no captures occurred when the trap was set for 2 days in early May. Field observations showed that the animals entered the trap but were able to reopen the drop-door and escape.

5.4.2.2 Treadle door in PVC pipe

One day of testing in mid-May resulted in the capture of 1 adult and 1 juvenile. However, gophers were able to bring down the treadle from inside the trap, and escape.

5.4.2.3 Drop-door with locking treadle

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On May 21, only 1 ground squirrel was captured during a 10-h test. Ground squirrels investigated the door but hesitated to enter.

5.4.2.4 Drop-door mounted on the side of the pen trap

A first test conducted on 28 June resulted in the capture of 6 ground squirrels in 10 minutes. In a second test on 30 June, 4 ground squirrels were captured in 3 hours. Animals showed no reluctance in entering the trap, and did not escape. This type of door was therefore adopted for tests with strychnine baits.

5.4.2.4 Pen trap-strychnine tests

A total of 12 and 14 juvenile ground squirrels were captured and ear-tagged in study plots nos. 29 and 30 (Table 1). Because these animals were all captured within 2 days, natural mortality was considered to be nil. Over a 7-day period, pen traps with strychnine baits controlled 58.3% and 50% of the original marked populations (Table 1). Control levels achieved with pen traps was not significantly different (P > 0.05) from those obtained with 0.4% Nu-gro strychnine baits, 0.4% Maxim strychnine baits, and RTU 0.4% strychnine baits. There was no poisoning of non-target animals.

6.0 PREDATION 6.1 Objectives

1. Badger:

Gather data on the badger population inhabiting the pasture-annual crop complex, including the female mentioned above and her young;

Investigate movements and hunting activities of a female badger (no. 207) captured in 2008 and those of neighbouring adults in a pasture-annual crop complex;

Estimate the impact of this badger population on the local ground squirrel population; and

Gather data on food habits of badgers across landscapes to assess its role as a predator of Richardson’s ground squirrels.

2. Long-tailed Weasel:

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Investigate movements and hunting activities of long-tailed weasels inhabiting the female badger’s pasture-annual crop complex mentioned above; and

Gather data on food habits of long-tailed weasels across landscapes to assess its role as a predator of Richardson’s ground squirrels.

3. Coyote:

Gather data on food habits of coyotes across landscapes to assess its role as a predator of Richardson’s ground squirrels.

4. Red Fox (Vulpes vulpes)8

Gather data on food habits of red foxes across landscapes to assess its role as a predator of Richardson’s ground squirrels.

6.2 Study plots

Data were collected at or nearby study plots used in toxicant (Section 3.0) and vegetation (Section 4.0) studies. Data on the female badger no. 207 were collected north of Hazenmore.

6.3 Methods

6.3.1 Badger

Estimates of badger densities were carried out in study plots used for the assessment of toxicants (Section 3.0) and grounds surrounding the home range of female no. 207. The distribution of animals was determined through animal search where signs of activity had been noted, and encounters when traveling through fields with study plots.

Because female no. 207 used the same burrow during all summer, information on its movements was limited. Habitat selection and distribution of activities (as indicated by burrow systems) were investigated at stand and landscape level. The number of Richardson’s 8 This species was not part of the original 2009 research proposal. Alpha Wildlife initiated the collection of scats in 2008, and continued in 2009 in order to provide SARM with a better understanding of the effect of terrestrial predators on Richardson’s ground squirrels.

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ground squirrel and badger holes present in the 3 m x 400 m grassland strip encompassing female no. 207 den was compared to that of two 3 m x 400 m control strips, located 15 m east and west of the den. In a study of habitat selection by an unknown badger, the number of Richardson’s ground squirrel and badger holes in 2 hunting grounds was compared to that of 2 controls located 30 m away, on each side of the hunting grounds. The size of hunting grounds and control quadrats was standardized at 70 x 70 m.

Knowing female no. 207’s home range in fall 2009 (Proulx et al 2009b) and summer 2010 (this study), a landscape section including annual crops and contiguous pasture land was identified. Five 350-m equidistant transects, ranging from 920 to 1265 m in length, were laid out (using 70-m-long rope sections) across crops and pastures in an east-west direction. All Richardson’s ground squirrel burrow holes located within 30 cm of either side of the rope were tallied. The same procedure was repeated with an unknown adult badger located 4 km east of female no. 207. Four 200-m-equidistant and 1618-m-long transects were laid across the landscape where the badger had been observed. Transects crossed fallow, alfalfa, wheat, and pasture fields. The length of the transects and their equidistance varied from one study site to another due to the presence of human dwellings, the location of the fields and their accessibility. The proportion of inventory transects within each field type was used to determine the expected frequency of ground squirrel burrow holes per field type. Chi-square statistics with Yates correction (Zar 1999) were used to compare observed to expected frequencies of burrow hole intersects per field type (Proulx & O’Doherty 2006). If the chi-square analysis suggested an overall significant difference between the distributions of observed and expected frequencies, a G test for correlated proportions (Sokal & Rohlf 1981) was used to compare observed to expected frequencies for each field type (Proulx 2006, 2009). Analyses of variances (ANOVA) and Tukey tests were used to compare the average numbers of Richardson’s ground squirrel holes in different field types fields of different types (Zar 1999).

The impact of badgers on ground squirrel populations was estimated solely9 on the basis of scats collected in 200810 and 2009. Scats were collected at burrows within and between toxicant study plots. Scat were dated, bagged, and kept frozen until processing. Scat analyses

9 Although we intended to capture badgers and implant transmitters to better understand their movements and assess the effect of their hunting activities on Richardson’s ground squirrel populations, we were unable to find badgers in safe locations, i.e., in fields where they would not be endangered by poison bait stations that producers disperse across fields to control ground squirrels. Most of the badgers present in spring had disappeared by early summer.

10 Due to time constraints, Proulx et al. (2009b) were not able to analyse all scats collected in 2008.

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were conducted at Alpha Wildlife Research & Management laboratory in Sherwood Park, Alberta. They were soaked overnight in mild water-bleach solution, washed through a sieve, and oven-dried at 75oC. Scats were analyzed according to Chandler (1916), Adorjan and Kolenosky (1969) and Moore et al. (1974). Comparisons of the frequencies (chi-square and Fisher tests; Siegel 1956) and mean volume per scat (Student’s t-test, Mann-Whitney U test, analysis of variance followed by the Tukey test; Siegel 1956, Zar 1999) of remains between different periods of the year were made (Proulx et al. 1987). Species richness in each habitat type was determined with the Shannon-Wiener function:

i

s

ii ppH 2

1log:

where s is the number of species, and pi is the proportion of total sample belonging to ith species (Krebs 1978).

A simple linear regression model was used to determine the relationship between some variables. Probability values ≤ 0.05 were considered statistically significant.

6.3.2 Long-tailed weasel, coyote and red fox

We were unable to investigate long-tailed weasel movements and hunting activities in no. 207 female badger’s pasture-annual crop complex due to the loss of animals to Rozol®+ poisoning11.

Scats of long-tailed weasel, coyote, and red fox that were collected in 20086 and 2009 were processed as per Section 6.3.1.

11 Our investigation of long-tailed weasels’ movements and hunting activities in no. 207 female badger’s pasture-annual crop complex was attempted in early July with the capture and radio-collaring of 2 weasels. Even though the pasture-annual crop complex was poison free, one male weasel died within 24 h of being collared. It was likely poisoned by Rozol®+. A neighbor had placed bait stations along the edges of the pasture-annual crop complex. A collared female disappeared during the same time period. In 2 study plots (nos. 3 and 11, Table 1) where the efficacy of Rozol® baits was tested, we captured 4 weasels. They all died within 48 h of being captured, <7 days after treating the study plot with Rozol® baits. All animals showed signs of internal bleeding.

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6.4 Results

6.4.1 Badger

6.4.1.1 Density of adult badgers in study plots

Observations on the distribution of badgers in study plots suggest a density of approximately 1 adult badger/quarter section (64 ha) in spring and summer (Table 7).

Table 7. Density of adult badgers in study plots, spring and summer 2009, southern Saskatchewan.

Time of Year

Number of badgers

Size of the area

Vegetation Location

Spring 1 1 quarter Section

Pure alfalfa and 70% alfalfa with crested wheat and brome

L. Thibault

Summer 3 3 quarter sections

Native grassland with crested wheat grass, sage, blueberry, rose (Rosa spp.).

O. Ballas

3 1 section

Native grassland dominated by crested wheat grass and buckbrush, and annual crops.

N. Mackenzie

G. Gross

6.4.1.2 Den site of female no. 207

The den was located within a 3-m-wide grassland strip that crossed a wheat field. Badger activities at the den could not be confirmed due to the animal’s shyness (it would seek refuge as soon as it heard a vehicle or saw human activity) and the height of the surrounding crop. There were 54 ground squirrel and 4 badger holes in a 3 m-wide x 400-m-long grassland strip encompassing the den. In one 3 m x 400 m control strip, only 10 ground squirrel holes were recorded. In the other control strip, 6 ground squirrel and 1 badger holes were found. Richardson’s ground squirrel and badger activity appeared to be greater in the grassland than in the wheat field.

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6.4.1.3 Habitat selection at landscape level

Female no. 207

Three types of vegetation cover were found within the landscape inhabited by female no. 207: grass and buckbrush were present in a coulee that was surrounded by wheat. A total of 158 Richardson’s ground squirrel holes were recorded along 5 survey transects (Table 8). The observed distribution of ground squirrel holes per vegetation type differed (2 = 50.2, df: 2, P < 0.001) from expected. Ground squirrel holes were significantly less frequent than expected in wheat (G = 4.7, df: 1, P < 0.05), but significantly more frequent in grass (G= 6.3, df:1, P < 0.02) and buckbrush (G= 6.64, df: 1, P < 0.02). Female no. 207 made a greater use of the coulee than the wheat fields, as it was found by Proulx et al. (2009b) in a study of the distribution of hunting grounds. In the coulee, however, the observed distribution of Richardson’s ground squirrel holes in grass and buckbrush was not significantly different (2= 50.2, df : 1, P > 0.05) from expected. Because hunting grounds were found in grass only (Proulx et al. 2009b), badger no. 207 appeared to select grass over buckbrush when hunting.

Unknown adult

Four types of cover were found within the landscape inhabited by an unknown adult badger: fallow, alfalfa, wheat, and pasture. A total of 288 Richardson’s ground squirrel holes were recorded along 4 survey transects (Table 8). The observed distribution of ground squirrel holes per vegetation type differed (2 = 77.1, df: 3, P < 0.0001) from expected. Ground squirrel holes were significantly less frequent than expected in wheat (G = 14.2, df: 1, P < 0.005), but significantly more frequent in fallow (G= 9.87, df:1, P < 0.01) and alfalfa (G= 9.23, df: 1, P < 0.01).

Two hunting grounds were found at the junction of the fallow-alfalfa fields, and in the alfalfa. The number of Richardson ground squirrel and badger holes was markedly higher in hunting grounds than in controls (Table 9). A significant relationship existed between the density of badger holes/ha and the density of Richardson’s ground squirrel holes/ha. The linear regression between densities was Y = 27.4 X + 31 (r = 0.93, P < 0.05) (Figure 6).

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Table 8. Distribution of Richardson’s ground squirrel burrow holes across landscapes inhabited by badgers, summer 2009.

Vegetation type Length (m)/% Number of Richardson’s ground squirrel burrow holes/%

Female no. 207

Wheat 5035 / 84.6 101 / 63.9

Grass 547 / 9.2 32 / 20.2

Buckbrush 370 / 6.2 25 / 15.8

Total 5952 / 100 158 / 100

Unknown adult

Fallow 768 / 11.9 65 / 22.6

Alfalfa 360 / 5.6 38 / 13.2

Wheat 2128 / 32.9 50 / 17.4

Pasture 3216 / 49.7 135 / 46.9

Total 6472 / 100 288 / 100

Table 9. Densities of ground squirrel and badger holes in 2 hunting grounds and respective control quadrats of an unknown adult badger, summer 2009.

Hunting ground no.

Number of Richardson’s ground squirrel holes

Number of badger holes

Hunting ground Control plots Hunting ground Control plots

1 54 14 14 0

26 0

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2 42 21 9 4

8 0

Figure 6. Relationship between the densities of badger and Richardson’s ground squirrel holes/ha, summer 2009.

6.4.1.4 Scat analyses

2008

Richardson’s ground squirrel remains decreased significantly (P < 0.02) in frequency from April-July to October-November. The August-September frequency of scats with ground squirrel remains was intermediary between spring-summer and fall (Table 10). The mean volume of Richardson’s ground squirrel was significantly larger (P < 0.05) in June-July (85.7 37.8%) than in October-November (16.9 37.3%). Although volumes of ground squirrel remains differed markedly during other periods (Table 10), differences were not significant (P > 0.05). Ground squirrels remains were most important in June-July. In October- November, small mammals and insects were frequent prey items. Also, the prey diversity index was markedly higher in fall than earlier in the year (Table 10).

2009

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Only a few scats were collected in 2009, and ground squirrel remains did not differ

(P > 0.05) in frequency and volume from April-May to June-July (Table 11). The diversity of prey items was slightly higher in April-May than in June-July (Table 11).

2008 vs. 2009

Richardson’s ground squirrel remains were similar (P > 0.05) in frequency in April-May of both years. However, the mean volume of ground squirrel remains in scats was significantly larger (t = 11.533, P < 0.05) in spring 2008 than in 2009. Ground squirrel remains were similar (P > 0.05) in frequency and volume in June-July of both years.

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Table 10. Frequencies and mean volumes (%) of food items in badger scats, spring-fall 2008.

Food item April-May*

n = 13

June-July*

n = 7

August-September*

n = 9

October-November*

n = 12


Mean volume - %


Mean volume - %


Mean

volume - %


Mean volume - %

MAMMALS


11 (84.6) 84.6 6 (85.7) 85.7 4 (36.4) 50 3 (23.1) 16.9

Sagebrush vole (Lemmiscus curtatus)

0 0 0 0 0 0 2 (11.1) 4.6

Deer mouse 0 0 0 0 0 0 1 (5.6) 7.5


(Reithrodontomys megalotis)

0 0 0 0 0 0 1 (5.6) 6.2

Badger** 1 (-) 1.5 1 (-) 1.6 1 (-) 0.1 4 (-) 11.2

White-tailed deer (Odocoileus virginianus)

0 0 0 0 0 0 1 (5.6) 7.7 (27.7)

BIRDS

Unidentified species

1 (7.7) 7.7 0 0 0 0 0 0

ARTHROPODS

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Insect 1 (7.7) 6.2 0 0 4 (36.4) 47.3 8 (44.4) 45.2

VEGETATION

Grass-type 0 0 1 (14.3) 12.7 3 (27.3) 2.5 1 (5.6) 2

MISCELLANEOUS

Unknown/

Pebbles

0 0 0 0 0 1 (5.6) 0.2


0.774 0.591 1.573 2.468

* Some scats contained more than one food item. ** Scats with few contents; badger was not considered a prey item.

Table 11. Frequencies and mean volumes (%) of food items in badger scats, spring-summer 2009.


n = 4

June-July*

n = 5


Mean volume - % Frequency (% of prey items)

Mean volume - %


3 (60.0) 50 4 (80.0) 80

Deer mouse 2 (40.0) 43.7 1 (20.0) 20

Badger** 1 (-) 6.3

Prey Diversity Index 0.971 0.722

* Some scats contained more than one food item. ** Badger was not considered a prey item.

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6.4.2 Long-tailed weasel

6.4.2.1 Density of long-tailed weasels in study plots

Observations on the distribution of long-tailed weasels in study plots and their immediate surroundings suggest a density of 1 weasel/quarter section (64 ha) in summer (Table 12). On the basis of visual observations, study plots with more than one capture were likely inhabited by a family.

Table 12. Distribution and density of long-tailed weasels in Ponteix and Hazenmore study plots.

Time of Year

Number of weasels

Size of the area

Vegetation Location

Summer >3 Quarter section

Seeded grassland dominated by crested wheat grass.

O. Ballas

1 Quarter Section

Seeded grassland dominated by crested wheat grass and alfalfa field.

O. Ballas

C. Knox

2

Quarter Section

Native grassland dominated by crested wheat grass and buckbrush, and annual crops.

N. MacKenzie


2008

Latrines

In June 2008, Proulx et al. (2009b) found that the average number of juvenile ground

squirrels (7 2.2 juveniles; range of 4 to 9) captured in 4 study plots (nos. 10, 13, 15 and 16)

with latrines was significantly lower (P < 0.005) than that of study plots (12.5 3.3 juveniles; range of 10 to 20) without latrines. On the basis of the analysis of a limited number

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of scats collected at latrines, Proulx et al. (2009b) showed that ground squirrels were the main prey of weasels in these study plots. The following corresponds to the analysis of all scats that had been collected at these 4 latrines in 2008.

Richardson’s ground squirrel remains were similar in frequency and volume in April-May and June-July 2008 in study plot no. 13 (Table 13). However, prey items were more diversified in summer (Table 13). There was no difference (2 = 6.3, df: 3, P > 0.05) in the frequency of ground squirrel remains in the summer scats of the latrines of study plots nos. 10, 13, 15 and 16. Mean volumes of ground squirrel remains in scats were similar (F3,113 = 2.054, P > 0.05) among study plots, and ranged from 71.9% to 94%. Other prey items were mainly small mammals and vegetation (Table 13).

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Table 13. Frequencies and mean volumes (%) of food items in long-tailed weasel scats from 4 study plots with latrines, 2008.

Food item

Study Plots

No. 13

No. 10

No. 15

No. 16

April-May*

n = 21

June-July*

n = 36

June-July*

n = 16

June-July*

n = 47

June-July*

n = 16


Mean volume - %


Mean volume - %


Mean

volume - %


Mean volume - %


Mean

volume - %

MAMMALS


15 (62.5) 65.5 34 (89.5) 87.5 12 (66.7) 71.9 44 (88.0) 94 15 (88.2) 89.1

Sagebrush vole

3 (12.5) 11.9 2 (5.3) 5.3 0 0 0 0 0 0

Deer mouse 3 (12.5) 10.7 1 (0.1) 2.0 0 0 1 (2.0) 2.1 0 0

Meadow vole (Microtus pennsylvanicu

0 0 0 0 4 (22.2) 21.9 0 0 0 0

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s)


0 0 1 (0.1) 2.6 0 0 0 0 1 (5.9) 6.2

ARTHROPODS

Insect 0 0 0 0 0 0 1 (2.0) 0.1 0 0

VEGETATION

Grass-type 3 (12.5) 11.9 1 (0.1) 2.6 2 (11.1) 6.2 4 (8.0) 3.8 1 (5.9) 4.7


1.549 0.398 1.224 0.680 0.642


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All scats

A total of 197 scats were collected from April to September 2008. The frequency of Richardson’s ground squirrel remains in scats was similar (P > 0.05) in April-May and June-July, but was significantly lower (P < 0.001) in August-September (Table 14). The highest prey diversity index was in August-September; the lowest was in April-May (Table 14). The mean volume of Richardson’s ground squirrel remains differed significantly (F2,193 = 24.599, P < 0.005) among periods. It was significantly larger (P < 0.05) in June-July (80.9 38.6%) than in April-May (60.8 46.0%) and August-September (23.1 42.9%). The April-May mean volume was also significantly (P < 0.05) higher than in August-September. Other prey included small mammals, insects and vegetation (Table 14).

Table 14. Frequencies and mean volumes (%) of food items in long-tailed weasel scats, spring-summer 2008.


n = 35

June-July*

n = 135

August-September*

n = 26


Mean volume - %


Mean volume - %


Mean

volume - %

MAMMALS


26 (59.1) 60.8 114 (79.7) 80.9 7 (25.0) 23.1

Sagebrush vole 5 (11.4) 11.4 6 (4.2) 4.4 9 (32.1) 34.6

Deer mouse 3 (6.8) 6.4 3 (2.1) 2.0 4 (14.3) 15.3

Meadow vole 1 (2.3) 2.9 4 (2.8) 3.0 0 0


0 0 3 (2.1) 2.2 0 0

BIRDS

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0 0 1 (0.7) 0.8 1 (3.6) 3.9

ARTHROPODS

Insect 0 0 2 (1.4) 0.8 6 (21.4) 19.3

VEGETATION

Grass-type 9 (20.5) 18.5 10 (7.0) 5.9 1 (3.6) 3.8


1.663 1.236 2.249


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2009

In April-May, all scats were found in the same portion of a Ponteix crested wheat field nearby a road with Rozol® bait stations. Only vegetation leftovers were found in the scats. In June-July, scats were collected in a Hazenmore pasture and in other crested wheat and alfalfa-crested wheat fields in Ponteix. Richardson’s ground squirrel remains differed

(P > 0.05) in frequency and volume between periods (Table 15). Prey index diversity was nil in spring, and 1.222 in June-July.

Table 15. Frequencies and mean volumes (%) of food items in long-tailed weasel scats, spring-summer 2009.


n = 15

June-July*

n = 18


Mean volume - % Frequency (% of prey items)

Mean volume - %)

MAMMALS


0 (0) 0 12 (63.2) 66.7

Deer mouse 0 (0) 0 4 (21.2) 22.2

West harvest Mouse 0 (0) 0 1 (5.3) 0.3

VEGETATION

Grass-like 15 (100) 100 2 (10.5) 10.8

Prey Diversity Index 0 1.222


2008 vs. 2009

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There was a significant difference (P < 0.005) in the frequency of Richardson’s ground squirrel remains in April-May of 2008 and 2009. In June-July, however, Richardson’s ground squirrel remains were similar (P > 0.05) in frequency (2 = 3.4, df: 1, P > 0.05) and volume (t = 1.420, P > 0.05) during both years.

6.4.3 Coyote


2008

Richardson’s ground squirrel remains decreased in frequency from April-July to October-November (Table 16). There was no difference (P > 0.05) between the frequency of scats with ground squirrel remains in April-May and June-July. Richardson’s ground squirrel remains were more often (P < 0.02) present in the June-July scats than in the August-September and October-November scats. Both April-May and October-November had a relatively high prey diversity index, and there was no difference (P > 0.05) between frequencies of scats with ground squirrel remains. The frequency of Richardson’s ground squirrel remains was similar (P > 0.05) in August-September and October-November.

The mean volume of Richardson’s ground squirrel remains decreased significantly (F3,46 = 8.705, P < 0.05) from spring to fall. The largest ground squirrel mean volume was in June-July, followed in order of decreasing importance by April-May (P > 0.05), October-November (P < 0.05), and August-September (P < 0.05). Mean volumes were similar (P > 0.05) in August-September and October-November.

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Table 16. Frequencies and mean volumes (%) of food items in coyote scats, spring-fall 2008.


n = 10

June-July*

n = 6

August-September*

n = 21

October-November*

n = 13


Mean volume - %


Mean volume - %


Mean

volume - %


Mean volume - %

MAMMALS


4 (23.5) 40.0 4 (50.0) 55.0 0 0 1 (4.3) 3.9

Northern grasshopper mouse (Onychomys leucogaster)

0 0 1 (12.5) 0.8 0 0 3 (13.0) 1.5

Deer mouse 1 (5.9) 10.0 0 0 3 (10.7) 10.5 1 (4.3) 0.8

Norway rat 0 0 0 0 0 0 1 (4.3) 7.3


3 (17.6) 20.3 0 0 0 0 0 0

Badger 1 (5.9) 10.0 2 25.0 0 0 4 (17.4) 8.4

White-tailed deer

0 0 0 0 0 0 1 (4.3) 6.9

Pronghorn (Antilocarpa americana)

0 0 0 0 0 0 1 (4.3) 3.8

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Cattle

(Bos taurus)

1 (5.9) 9.5 0 0 1 (3.6) 0.5 1 (4.3) 7.7

ARTHROPODS

Insect 5 (29.4) 0.5 1 (12.5) 15.8 20 (71.4) 80.1 9 (39.1) 51.9

VEGETATION

Grass-type 2 (11.8) 9.7 0 0 4 (14.3) 8.8 1 (4.3) 7.6

MISCELLANEOUS

Pebbles** 0 0 0 1 (3.6) 0.1 1 (4.3) 0.2


2.538 1.750 1.266 2.717

* Some scats contained more than one food item. ** Not considered a prey item.

2009

Only 6 scats were collected in April-May, and they did not contain remains of Richardson’s ground squirrels (Table 17) Prey were diversified.

A total of 57 scats were collected at a coyote den in July 2009. Richardson’s ground squirrel remains were dominant, followed in importance by small mammals (Table 17). Prey diversity index was estimated at 1.263.

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Table 17. Frequencies and relative volumes (%) of food items in coyote scats, spring-summer 2009.


n = 6

June-July*

n = 57

Frequency

(% of prey items)

Mean volume - % Frequency

(% of prey items)

Mean volume - %


0 0 43 (72.9) 74.0

Deer mouse 1 (14.3) 5.0 7 (11.9) 12.3

Western harvest mouse 1 (14.3) 11.7 5 (8.5) 8.8

Badger 1 (14.3) 16.6 0 0

White-tailed deer 1 (14.3) 16.6 0 0

Cattle 1 (14.3) 16.6 0 0

Insect 2 (28.6) 33.3 0 0

Vegetation 4 (6.8) 4.9

Prey Diversity Index 2.523 1.263


2008 vs. 2009

There was no significant difference (P > 0.005) in the frequency and mean volume of Richardson’s ground squirrel remains in April-May of 2008 and 2009.

6.4.4 Red fox

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In 2008 and 2009, investigations of red fox food habits focused on dens only. In 2008, despite extensive search, only 2 dens were found. In 2009, red foxes were more abundant, and 8 dens (1 in spring, 7 in summer) were found.

2008

Mankota den – Richardson’s ground squirrel remains were similar (P > 0.05) in frequency and volume in spring and summer (Table 18). During both periods, ground squirrel remains represented 50% of prey items. The prey diversity index was 1.844 in April-May, and 1.906 in June-July.

Kincaid den – Only June-July scats were collected at this den. Food habits were diversified but ground squirrel remains were dominant (Table 18).

Mankota vs. Kincaid dens – There was no significant difference (P > 0.005) in frequency and mean volume of Richardson’s ground squirrel remains in June-July scats of Mankota and Kincaid. Prey diversity index was slightly lower in Kincaid scats (Table 18).

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Table 18. Frequencies and mean volumes (%) of food items in red fox scats, spring-summer 2008.

Mankota Den Kincaid Den


n = 6

June-July*

n = 41

August-September*

n = 41


Mean volume - %


Mean volume - %


Mean

volume - %

MAMMALS


3 (42.9) 50 30 (63.8) 68.8 35 (71.4) 76.3

Red-backed vole

(Clethrionomys gapperi)

0 0 1 (2.1) 2.4 0 0

Deer mouse 2 (28.6) 17.5 6 (12.8) 14.6 4 (8.2) 6.6


1 (14.3) 16.7 2 (4.3) 2.9 3 (6.1) 5.0

Badger 0 0 1 (2.1) 1.2 0 0

Mule deer (Odocoileus hemionus)

0 0 1 (2.1) 2.4 0 0

BIRDS


0 0 2 (4.3) 0.7 2 (4.1) 4.9

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ARTHROPODS

Insects 3 (6.4) 5.6 2 (4.1) 4.6

VEGETATION

Grass-type 0 0 1 (2.1) 1.2 3 (6.1) 2.7


1.844 1.906 1.513


2009

Mankota den – Thirteen scats were found in April-May only; the den became inactive in June. Ground squirrel remains were present in only 5 (38.5%) of scats. Prey index diversity was 1.826 (Table 19).

All summer dens – Richardson’s ground squirrel remains were similar (P > 0.05) in frequency and volume among all dens (Table 19). Ground squirrel remains represented > 60% of prey items. The prey diversity index ranged from 1.164 to 1.967 (Table 19).

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Table 19. Frequencies and mean volumes (%) of food items in red fox scats in spring-summer 2009 dens.

Food item

Study Plots

Mankota Kincaid Hazenmore 1 Hazenmore 2 Hazenmore 3 Hazenmore 4 Aneroid Ponteix

April-May*

n = 13

June-July*

n = 21

June-July*

n = 64

June-July*

n = 17

June-July*

n = 47

June-July*

n = 53

June-July*

n = 28

June-July*

n = 86


Mean volume - %


Mean volume - %


Mean

volume - %


Mean volume - %


Mean

volume - %


Mean

volume - %


Mean

volume - %


Mean

volume - %

MAMMALS


5 (38.5) 38.5 13 (54.2) 61.0 50 (74.6) 78.1 14 (70.0) 82.2 36 (73.5) 76.6 37 (66.1) 69.8 17 (60.0) 60.7 60 (67.4) 69.4

Sagebrush vole

0 0 0 0 0 0 0 0 0 0 1 (1.8) 1.3 0 0

Deer mouse 3 (23.1) 23.1 2 (8.3) 7.4 6 (9.0) 9.1 1 (5.0) 5.9 7 (14.3) 14.9 5 (8.9) 8.3 7 (24.1) 22.9 25 (28.1) 28.9

Meadow vole

0 0 0 0 0 0

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4 (30.8) 30.8 1 (4.2) 4.8 4 (6.0) 6.3 2 (10.0) 9.4 2 (4.1) 4.3 2 (3.6) 3.8 2 (6.9) 7.2 1 (1.1) 1.2

White-tailed jackrabbit (Lepus townsendii)

0 0 0 0 0 0 0 0 0 0 1 (1.8) 1.9 0 0

Deer (Odocoileus spp.)

0 0 4 (16.7) 19.0 1 (1.5) 1.6 0 0 0 0 0 0 0 0

Pronghorn 0 0 1 (4.2) 4.8 0 0 0 0 0 0 0 0

Cattle 0 0 0 0 0 0 0 0 0 0 1 (1.8) 1.9 0 0

BIRDS


1 (7.7) 7.7 0 0 2 (3.0) 1.6 0 0 1 (2.0) 0.1 5 (8.9) 8.7 2 (6.9) 7.1

ARTHROPODS

Insect 0 0 0 0 1 (1.5) 1.6 2 (10.0) 0.2 0 0 2 (3.6) 3.8 0 0 2 (2.2) 0.2

VEGETATION

Grass-type 0 0 3 (12.5) 3.1 3 (4.5 1.8 1 (5.4) 2.4 3 (6.1) 4.2 2 (3.6) 0.6 1 (3.0) 2.1 1 (1.1) 0.3

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1.826 1.967 1.407 1.456 1.275 1.848 1.621 1.164

* Some scats contained one than one food item

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2008 vs. 2009

Richardson’s ground squirrel remains were similar in frequency (2 = 9.2, df: 8, P > 0.05) and volume (F8, 389 = 0.838, P > 0.05) among all June-July dens of 2008 and 2009. The mean volumes of 2008 and 2009 June-July scats were 72.6% and 71.6%, respectively.

7.0 DISCUSSION

The 2009 field work confirmed our assessment of toxicants in 2007 and 2008. While many Rodenticides are available on the market, some of them have more potential than others when they are used under favorable environmental conditions and site preparation.

Phostoxin® – This toxicant certainly has the potential to efficiently control Richardson’s ground squirrels, particularly in spring when soil moisture is higher. This is consistent with Salmon and Schmidt’s (1984) recommendations. However, it is essential to flag the ground squirrel burrow holes in order to ensure total treatment. When treatment is conducted in fields where burrow holes have not been flagged, time is lost trying to find openings. When holes are missed, ground squirrels may receive a sub-lethal dose of gas and escape. We found that it is better to treat fields early in the morning, just before sunrise, when ground squirrels are still sleeping. In the evening, some animals are still up and may not be treated. During warm temperatures, it is easier to work in the morning with protective equipment. Nevertheless, applying Phostoxin® pellets is time-consuming, and one must limit the treatment to small areas ( 1 ha) where ground squirrel concentrations are higher.

Chlorophacinone – Past studies reported conflicting results about the ability of chlorophacinone to control ground squirrel populations (O’Brien 1979, Johnson-Nistler et al. 2005). In the last two years, we have demonstrated that this anticoagulant (Rozol® and Ground Force®) was very effective to control Richardson’s ground squirrel populations. In grasslands, it consistently controlled > 70% of the animals, although it is better to use it in spring when there is less green vegetation. The 2008 study showed that the use of bait stations is less time-consuming than hole baiting, but it is more costly due to overfeeding of ground squirrels and non-target species. Hole baiting is very effective, and the 2009 spring tests showed that >70% control can be obtained at half concentrations. This is because one animal may use several holes. Hole baiting is creating small bait stations that animals visit and use over a 2-day period, before the second treatment. However, two problems are associated with chlorophacinone. First, this toxicant is not as effective when it is used in pure or mixed alfalfa fields. Plants rich in vitamin K (e.g., alfalfa)

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counteract the effect of anticoagulants on ground squirrels (Arjo and Nolte 2004). In 2009, chlorophacinone was more effective than usual in alfalfa because plants were dying due to drier conditions. On the other hand, on average, Ground Force® appeared to be more effective than Rozol® in alfalfa fields, possibly because winter wheat is more attractive to ground squirrels than oats, and does not have enzymes that may interfere with the stability of chlorophacinone (Liphatech Inc., 2008, personal communication). Concerns with the use of anticoagulants relate to primary poisoning of non-target species (e.g., small mammals and granivore birds) and secondary poisoning of predators (e.g., birds of prey and terrestrial carnivores) (Proulx and MacKenzie 2009). When anticoagulants are used over large areas, as is the case in southwest Saskatchewan, loss of predators may occur across landscapes and have a long-term impact on ground squirrel management. For this reason, it is more appropriate to use anticoagulants in sites with larger concentrations of ground squirrels in order to stop their expansion and invasion of surrounding fields. It is essential that moribund animals be removed; these animals usually appear on surface 3 days after first field application.

Strychnine – After 3 years of research in southwest Saskatchewan (Proulx and Walsh 2007, Proulx et al. 2009a, and this study), there is no doubt that RTU baits are ineffective to control ground squirrel populations. In contrast, FM strychnine-treated oats were found effective in 2008, when we used a freshly produced strychnine solution. In 2007, when the product was 5 years-old, the efficacy of FM strychnine dropped significantly and control levels were similar to those obtained with RTU baits. When the strychnine solution was 1 year-old, its control efficacy dropped slightly. Overall, FM strychnine meets the acceptation criteria of this research program. However, one must wonder about the unreliability of the product once it has been stored over winter. Is strychnine, or the anise oil attractant, lost over time? More research with freshly produced strychnine needs to be conducted in the future to ascertain its ability to control 70% of ground squirrel populations. Work conducted in 2008 (Proulx et al. 2009a) and this year showed that it is not advantageous to change bait. Hulless oats are as attractive to ground squirrels as canary seeds (Proulx et al. 2009a), and more attractive than alfalfa pellets (this study). However, compliance analyses should be conducted to ensure that strychnine solutions are appropriate. One major problem associated with strychnine is its impact on non-target species, and its secondary persistence (Proulx and MacKenzie 2009). In order to minimize non-target poisoning, and the loss of predators (particularly birds of prey), it is essential to develop a delivery system that confines poisoned animals to an area that is not accessible by other wildlife species. This study showed that the use of a multi-capture pen trap would help greatly in reducing non-target species poisoning. Because the ground squirrels die in the trap, predators and scavengers cannot access them and be poisoned. Of course, the true efficacy of the pen trap still needs to be assessed with freshly produced strychnine baits, and over large areas. The current use of strychnine is time-consuming and labor-intensive as it requires that bait be deposited in

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burrow holes and covered with dirt. Such a protocol is almost impossible to implement over large areas. There is a need to render baits more attractant to ground squirrels, particularly if they are used in pen traps. Freshly produced strychnine, and the use of attractants and additives to increase bait acceptability and consumption, should be considered for the long-term use of this toxicant.

When we initiated toxicant investigations in 2007, farmers and government agencies had many questions about the efficacy of various toxicants. Due to limited time and resources, it was impossible to assess all toxicants over a short time period and in many sites. We decided to test poisons over time, using a few study plots every year, and under different environmental conditions. This was a successful approach as it allowed us to assess poisons under diverse temperatures and moisture regimes, in various crops, with different baits, and with different product generations. On an annual basis, because tests were conducted in a few study plots only, decisions to further investigate some poisons were based on limited statistical analyses and observations. However, after 3 years of research, complete datasets suggest that the right decisions were made year after year. This research program allowed us to assess limitations in the application of Phostoxin®, and advantages and risks associated with the use strychnine and anticoagulants. This research program also allowed us to develop an evaluation protocol based on capture-recapture of ground squirrels. The most difficult aspect of the research was to deal with natural predation during testing. In 2009 and 2010, high natural predation levels resulted from a concentration of predators in some study plots. For example, in 2009, one control study plot was inhabited by two badgers, one weasel family, nesting Swainson’s hawks (Buteo swainsoni), and 1 red fox. In 2010, 8 ferruginous hawks (Buteo regalis), 1 badger, 2 cats and 1 dog were seen daily in one control study plot. Although natural predation levels varied from year to year, it had to be taken into consideration to properly assess the true efficacy of toxicants to control ground squirrel populations.

Phostoxin®, Rozol®, Ground Force®, and FM Nu-gro strychnine should be used judiciously in order to be effective, to minimize non-target hazards, and to be cost-effective (see Witmer et al. 2007). Ramsay and Wilson (2000) discussed ecologically-based baiting strategies for rodents in agricultural systems.

7.2 Ground squirrel-Vegetation Height Relationship

Although the number of burrow openings is not an absolute estimate of Richardson’s ground squirrel densities, they are a reliable approximation of the size of populations, i.e., light or heavy infestations. Downey et al. (2006) found that ground squirrels selected against areas with tall grass (>30 cm). Our study showed that the presence of ground squirrels dropped

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significantly when vegetation reached a minimum height of only 15 cm. This is in agreement with Proulx and MacKenzie’s (2009) findings. Richardson’s ground squirrels prefer to establish their burrow systems in fields with shorter vegetation and good visibility (Yensen and Sherman 2003). At the management level, this suggests that, in drought-stricken zones such as the communities of southwest Saskatchewan (Liu et al. 2004, Barrow 2009), rotational grazing, the seeding of a mixture of improved species of grasses and legumes, and the maintenance of dense grass cover (Heath et al. 1973) will reduce ground squirrel colonization and produce high quality forage that is more resistant to drier environmental conditions.

7.3 Assessment & Development of Capture-efficient Trapping devices

Concerns about the welfare of trapped animals is a major concern for the public, environmental groups, and scientists (Schmidt and Bruner 1981, Proulx and Barrett 1989, Iossa et al. 2007). As there are few killing traps for ground squirrels available on the market, the assessment of the ability of the GT2006 traps was essential. This trap is humane and can quickly render unconscious Richardson’s ground squirrels struck in the head region. One must be patient when using it. Ground squirrels that sought refuge in their burrow system do not always come back immediately, and they do not always use the same opening to exit their burrow system. It is therefore necessary to use several traps at the same time to capture one individual. At landscape level, the use of the GT206 would require hundred of traps and the operation would be time-consuming and labor-intensive. We recommend that this trapping device be used for the control of ground squirrels in areas where chemical control is not a solution, and for small population concentrations.

Compared to the GT2006, the multi-capture pen trap is not labor-intensive. The trap remains functional capture after capture. When captive ground squirrels feed on strychnine bait, they die within the trap and have no impact on other wildlife. Tests with the pen trap and strychnine showed that control levels were similar to those obtained with strychnine placed in burrow openings. It is, however, less time-consuming. The development of the pen trap was not simple. It took into consideration the behavior of ground squirrels approaching foreign objects, and their ability to escape. An industrial version of the prototype trap should be produced and its capture efficiency should be evaluated with different attractants. The pen trap should also be tested with freshly produced strychnine baits to assess its ability to attract, capture and dispatch ground squirrels. Finally, it is important to determine how far apart traps should be set, and how often they should be moved, to effectively control ground squirrel populations over large areas.

7.3 Predation

The 2009 research program demonstrated once more that chemical control of ground squirrel populations may impact on the sustainability of predator communities. Where predators are abundant, and particularly where they have coevolved with the prey species, density-dependent or delayed density-dependent predation may impact on large fluctuations of rodent

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population densities (Witmer and Proulx 2010). Ferruginous hawks are specialist predators feeding almost exclusively on Richardson’s ground squirrels (Lokemoen and Duebbert 1976, Schmutz et al. 1980). Birds of prey may succumb to strychnine and anticoagulant poisoning (Proulx and MacKenzie 2009, Proulx et al. 2009a, and this study). This is also true for badgers, long-tailed weasels, and foxes (Proulx and MacKenzie 2009). Also, a decrease in predator populations certainly contributed to the expansion of ground squirrel populations during 2000-2009 in southwest Saskatchewan. Chemical control must therefore be judiciously used across landscapes.

This study showed that badger, long-tailed weasel, and red fox food habits consisted mainly of ground squirrels in spring and summer. Scat analyses showed that ground squirrels were an important prey in June-July. However, all predators changed their diet starting in August, when ground squirrels retired for the winter. Small mammals and insects then became more important. It is interesting to note that vegetation was a constant component of long-tailed weasel diets. In 2009, however, weasel scats contained vegetation only, a finding that we cannot explain. Coyotes did not appear to be as effective as the other terrestrial predators, but they may still have an impact on ground squirrel populations when they have their pups.

Our findings suggest that depredation of ground squirrels by red foxes may have been underestimated by wildlife managers. Red fox feeding habits vary markedly with annual and seasonal availability of food items. While reviews of diets usually list small mammals and insects as important food items, ground squirrels are not listed as main prey (Samuel and Nelson 1982, Cypher 2003). The red fox-ground squirrel relationship warrants further investigations. It is known that some red fox dens may be used over multiple generations (Stanley 1963) and may be enlarged each year (Pils and Martin 1978). Also, movement patterns within home ranges are strongly influenced by the distribution of food resources (Ables 1975). If red foxes become specialist predators of ground squirrels when they have their pups, then they could play an important role in the control of this species along field edges and fences. It appears that fox population densities were much higher in 2009 than in previous research years. This may be a delayed ground squirrel density-dependent population irruption, or the result of an apparent decrease in coyote numbers (Sargeant et al. 1987) due to control by local farmers.

Our findings on multi-scale habitat selection by badgers confirmed Proulx et al.’s (2009b) findings that badgers do not establish their home range and hunting grounds at random. Their distribution across landscapes indicates that they associate with larger concentrations of Richardson’s ground squirrels, and therefore aim to maximize their foraging activities. Multi-scale habitat selection was also found with other mustelids (Lofroth 1993, Weir and Harestad 2003). On the basis of this finding, we suggest that multi-scale habitat selection by badgers be further investigated with more animals in different environments.

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While estimated badger and weasel densities were similar in 2009 and 2010, more data on their distribution and numbers should be collected in landscapes where ground squirrels are not poisoned. Such information would be useful in the development of an Integrated Pest Management Program (Witmer and Proulx 2010).

8.0 ACKNOWLEDGEMENTS Advancing Canadian Agriculture & Agri-Food in Saskatchewan (ACAAFS) (as a Collective Outcome Project with AFC in Alberta), the Alberta Ministry of Agriculture & Rural Development (Agriculture Development Fund) and Saskatchewan Association of Rural Municipalities (SARM) provided funding for this work. We thank Nu-Gro Corporation, Maxim Chemical International Ltd., and Degesch America Inc. for providing toxicants. We are grateful to Scott Hartley from Saskatchewan Agriculture, Rick Jeffery from Pest Management Regulatory Agency (PMRA), and Dale Harvey from SARM for facilitating research logistics. We thank farmers L. Thibault, C. Lamb, F. Therrien, D. MacMillan, O. Balas, C. Knox, and G. Gross for allowing us to conduct this project on their farmlands. We also thank Kenneth Rice from PowerSource Performance Inc. for equipment maintenance.

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relationships among predators, prey and habitat use … · frequencies for each habitat class....

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