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WOODLAND CARIBOU(Rangifer tarandus caribou)

Prepared for Millar Western Forest Products’Biodiversity Assessment Project

Prepared by:

P.E. Higgelke and H.L. MacLeod

KBM Forestry Consultants Inc.Thunder Bay, Ontario

May 2000

Source: Smith (1993)

Table of Contents

1.0 CONSERVATION AND THE EFFECT OF FOREST ACTIVITIES . 1

1.1 Introduction .............................................................................. 1

1.2 Effects of Forest Management Activities ................................... 2

2.0 HABITAT USE INFORMATION ................................................. 3

2.1 Food Requirements ................................................................... 3

2.2 Cover Requirements .................................................................. 3

2.3 Reproduction Requirements ..................................................... 4

2.4 Habitat Area Requirements ....................................................... 4

2.5 Landscape Configuration Requirements ................................... 5

2.6 Sensitivity to Human Disturbance ............................................. 5

3.0 MODEL ...................................................................................... 6

3.1 Envirogram ................................................................................ 6

3.2 Application Boundaries ............................................................. 6

3.3 Model Description ..................................................................... 9

3.4 Habitat Variable SIs ................................................................ 11

3.5 Computation ........................................................................... 16

4.0 EXTERNAL REVISION ............................................................18

5.0 LITERATURE CITED ...............................................................20

List of FiguresFigure 1. Present and historic Woodland Caribou distribution in Alberta (AE 1999). ................ 1

Figure 2. Envirogram of Woodland Caribou summer habitat based on available information forHSM development............................................................................................. 7

Figure 3. Envirogram of Woodland Caribou winter habitat based on available information for HSMdevelopment. ................................................................................................... 7

Figure 4. Envirogram of Woodland Caribou reproductive habitat based on available information forHSM development............................................................................................. 8

Figure 5. HSM structure for Woodland Caribou summer habitat in Millar Western’s FMA area. 9

Figure 6. HSM structure for Woodland Caribou winter habitat in Millar Western’s FMA area. 10

Figure 7. HSM structure for Woodland Caribou reproduction habitat in Millar Western’s FMA area.10

Figure 8. Woodland Caribou foraging habitat suitability in relation to lichen cover within MillarWestern’s FMA area. ....................................................................................... 11

Figure 9. Woodland Caribou foraging habitat suitability in relation to shrub cover within MillarWestern’s FMA area. Weighting: 0 - 3 m = 1, > 3 m = 0.2. .............................. 12

Figure 10. Woodland Caribou foraging habitat suitability in relation to sedge cover within MillarWestern’s FMA area. ....................................................................................... 12

Figure 11. Woodland Caribou foraging habitat suitability in relation to forb cover within MillarWestern’s FMA area. ....................................................................................... 13

Figure 12. Woodland Caribou foraging habitat suitability in relation to arboreal lichen cover withinMillar Western’s FMA area. ............................................................................... 13

Figure 13. Woodland Caribou cover habitat suitability in relation to developmental stage within MillarWestern’s FMA area. ....................................................................................... 14

Figure 14. Woodland Caribou cover habitat suitability in relation to tree species composition withinMillar Western’s FMA area. ............................................................................... 14

Figure 15. Woodland Caribou cover habitat suitability in relation to tree species composition withinMillar Western’s FMA area. ............................................................................... 15

Figure 16. Woodland Caribou hiding cover suitability in relation to proximity to road within MillarWestern’s FMA area. ....................................................................................... 15

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Woodland Caribou HSM

Higgelke and MacLeod

1.0 CONSERVATION AND THEEFFECT OF FORESTACTIVITIES

1.1 Introduction

In Alberta, the caribou (Rangifer taranduscaribou) occurs at low densities and has beenidentified as a vulnerable species (Bradshawet al. 1995; Rettie and Messier 1998). Theneed for increased attention to caribou wasmade clear when census results in 1990 re-vealed that caribou populations had declinedby 50 to 75% since 1970 (Edmonds 1988;Van Tighem 1990).

The historical range of the caribou extendedsouth and east from Alaska through the GreatLakes region to New England (Servheen andLyon 1989). Presently, however, it has beendrastically reduced in the United States withall caribou existing north of the Canadian bor-der except for one herd that continues toinhabit the Selkirk Mountains of Idaho (Figure1, Servheen and Lyon 1989). As this reduc-tion in range has occurred gradually since Eu-ropean settlement, it has been attributed tohuman activity (Edmonds 1988; Bradshaw etal. 1995; Rettie and Messier 1998).

In west-central Alberta, there are nine recog-nized caribou ranges: Calahoo, Narraway,Lingrell, Redrock/Prairie Creek, A la Peche,Little Smoky, North Jasper, South Jasper/WhiteGoat, and North Banff/Siffleur (Brown andHobson 1998). Of these groups, all but oneare referred to as Mountain Caribou as theyuse, for at least part of the year, mountain-ous terrain. The Little Smoky herd is the onlygroup that behaves as Woodland Caribouutilising fens, muskegs, and coniferous standswithin the boreal forest. Until recently, it wasthought that caribou did not exist within MillarWestern’s FMA area. Summer use of themost westerly portions of the FMA area hasnow been confirmed, however (Smith pers.comm. 1999). As the Little Smoky herd’srange is located only 100 km west ofWhitecourt, it can be assumed that any cari-bou inhabiting Millar Western’s FMA area willbehave, and select habitat, as Woodland Cari-bou.

Figure 1. Present and historic Woodland Caribou distribution in Alberta (AE 1999).



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The habitat requirements of caribou in Albertahave not yet been quantified to a great ex-tent (Smith pers. comm. 1999). In particular,a recent report prepared for the ResearchSubcommittee of the West-central AlbertaCaribou Standing Committee has stated thatthree questions are in need of answer: Whatdo caribou need in terms of habitat require-ments? How do caribou respond to humanactivity and changing landscapes? How arecaribou populations changing over time (Brownand Hobson 1998)? At the present time, nu-merous research projects are underway inan effort to learn more about this species.This HSM will, therefore, require continual ad-justment as new information becomes avail-able.

1.2 Effects of ForestManagement Activities

When timber harvesting occurs within caribouwintering areas, the capability of the stand tointercept incoming snow is reduced. There-fore, clearcutting of a stand eliminates its in-terception capability. Although caribou are tol-erant of deep snow, they may choose toforage where snow is shallower and may avoidsnow with a crusted surface that does notsupport their weight in order to conserve en-ergy. Therefore, the true value of winter for-est cover is its capability to intercept snowand temper the freeze/thaw cycles that leadto snow hardening. In addition, the produc-tivity of lichens, the caribou’s major winterfood source, is thought to be negatively im-pacted by timber harvesting (Cumming 1992).Smith et al. (1998) found that caribou ap-pear to avoid clearcuts and tend to moveaway from harvested areas.

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2.0 HABITAT USE INFORMATION

2.1 Food Requirements

With respect to its feeding habits, the caribouis considered a ‘grazer’. Its foraging require-ments differ with the seasons.

During spring and summer, the WoodlandCaribou feeds on nutritious forbs, leaves ofdeciduous shrubs, sedges, lichens, and fungi(Duquette 1985; Thomas et al. 1996; Rettieet al. 1997). These materials are readily avail-able at this time and caribou are not normallyrequired to travel long distances in search ofsuitable foods (Edmonds 1988; Stuart-Smithet al. 1997).

During winter, the caribou’s metabolic rate isreduced to only 75% of the summer rateand food energy is used more for body weightmaintenance than for growth (Duquette1985). The animal, therefore, seeks high car-bohydrate, low protein foods composed pre-dominantly of arboreal and terrestrial lichenswith supplements of sedges (Duquette 1985;Thomas et al. 1996). It is predominantly the‘reindeer lichens’ of the genus Cladina thatare consumed by the caribou (Cumming1992).

Though lichens have the ability to grow undera range of environmental conditions, they arepoor competitors and are quickly replaced bymosses and vascular plants in nutrient-rich,moist environments (Harris 1996). They are,therefore, most abundant in older coniferousstands (80 to 120 years old, Brown andHobson 1998), with less than 50% canopyclosure and thin mineral soils (Duquette 1985).Slope and aspect are also related to lichendensity as Cladina spp. are able to reach theirgreatest abundance on dry, upper slopes andsouth-facing exposures (Harris 1996).

The caribou is well adapted for snow. Theanimal must dig through accumulated snowto access its food resources using an actiontermed ‘cratering’ (Cumming 1992). It is ableto smell lichens and can crater successfully

through 100 cm of snow. Where snow depthis excessive, however, caribou will quickly turnto arboreal lichens (Smith pers. comm. 1999).Therefore, foraging habitat includes areas ofhigh terrestrial and arboreal lichen productiv-ity as well as shrub and herbaceous vegeta-tion availability. Since energy conservation isbest achieved when less cratering is requiredto reach lichens, forest stands that provideeffective snow interception are beneficial(Smith pers. comm. 1999).

2.2 Cover Requirements

Hiding Cover

The caribou uses a strategy different thanother cervids for predator evasion. Elk,moose, and deer in west-central Alberta pre-fer to hide within dense forest cover, whereasthe caribou tend to disperse at low densitiesover the range. Though the hunting successof the caribou’s major predator, the wolf, isreduced by this method, caribou populationsare still strongly influenced by predation (Brownand Hobson 1998). In fact, wolves have beenassociated with up to 22% of annual adultmortality of the Little Smoky herd during aperiod when recruitment rate was 15%(Edmonds 1988).

Forest Cover

Caribou in west-central Alberta have beenknown to successfully feed and move throughsnow of significant depth (Smith pers. comm.1999) and it is uncommon for them to be-come stressed by cold temperatures (Brownpers. comm. 1999). Therefore, the animalsdo not generally select habitat for thermalregulation. Instead, they will choose homeranges based on food supply. As previouslymentioned, in mature coniferous stands(spruce or pine) with less than 50% canopyclosure, abundant lichens are available(Duquette 1985; Brown and Hobson 1998).



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Though muskeg environments may also beused, forested areas are preferred when snowis sufficiently deep or crusted to influence thecaribou in open areas (Brown and Hobson1998).

The Little Smoky caribou herd is known touse similar cover habitat types year-round.In summer, the animals may seek shelterfrom heat, provided by the shady conditionsof coniferous stands (Smith pers. comm.1999). In winter, these stands also temperthe snow pack. In early winter, before snowdepth and hardness begins to impact the cari-bou, they may preferentially use muskeg habi-tats.

Studies in west-central Alberta have revealedthat mixed-coniferous stands of spruce and/or pine and muskeg environments are usedin the following proportions in all seasons:

♦ Mixed-coniferous (spruce and pine) = 16to 40% of observations;

♦ Relatively pure pine stands = 19 to 51%of observations; and

♦ Muskeg habitat = 13 to 31% of obser-vations.

2.3 Reproduction Requirements

The fall migration of the caribou occurs inmid-September, just prior to the breeding sea-son. In west-central Alberta, the rut occursfrom mid-September to mid-October and ismost often associated with open muskeg en-vironments (Edmonds 1988).

Between mid-April and mid-May, pregnantfemale caribou begin their journey from thewintering range to a selected calving site thatis often within 100 m of muskeg (Edmonds1988; Smith pers. comm. 1999). Calving sitesare usually located in isolation from other cari-bou (Boonstra and Sinclair 1984; Edmonds1988). The attraction to open muskeg areasis probably related to the caribou’s height-ened ability to perceive incoming predators(Edmonds 1988). Muskeg with open water isparticularly desirable as the caribou and its

calves are offered the opportunity to quicklyescape from predators (Duquette 1985;Edmonds 1988).

The cow and its calves may remain withinthe calving site for several weeks (Duquette1985). As the nutritional requirement of themother and calves is high during this time,the calving site should be located close to aplentiful supply of lichens (Servheen and Lyon1989). Like most ungulates, caribou time theircalving efforts with the onset of green-up sothat protein-rich herbaceous and shrubby veg-etation is available for consumption during lac-tation. In spring, these food items first be-come available near muskeg, well sites orcutlines, and on south-facing slopes (Smithpers. comm. 1999). Calving sites are gener-ally located near or within the summer range(Duquette 1985; Edmonds 1988).

2.4 Habitat Area Requirements

The total range of the Little Smoky Herd,inhabiting the forests along the Little SmokyRiver just west of the Millar Western FMAarea, is 2,800 km2 (Alberta Natural Re-sources Service unpubl. data). This esti-mate includes both summer and winterhabitat for a herd of approximately 60 to100 individuals. The winter and summerranges of Woodland Caribou tend to overlapsignificantly with their centres generally lessthan 12 km apart (Brown and Hobson1998). Mean winter and summer rangesizes for individual radio-collared caribou inthe Little Smoky herd are 168 km2 and 24km2 (N = 17) respectively (Alberta NaturalResources Service unpubl. data). Theseindividual home ranges overlap to formseasonal herd ranges (Darby and Pruitt1984; Edmonds 1988).

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2.5 Landscape ConfigurationRequirements

A review of west-central Alberta’s caribou re-search has shown that the Woodland Caribouuses spruce and/or pine forests and treedmuskegs as foraging and cover habitatsthroughout the year. Though dense conifer-ous forests may be more important in yearswith significant snowfall, open muskegs maybe preferentially, but not exclusively, usedduring milder portions of the winter. In west-central Alberta, mature coniferous forest isthe most commonly used habitat in late win-ter regardless of snow conditions (AlbertaNatural Resources Service unpubl. data).Thus, both open muskeg and mature conif-erous forest should be available within thehome range, giving the animals the opportu-nity to inhabit the type appropriate to thecurrent environmental conditions.

During the calving season, caribou in the LittleSmoky herd often choose calving sites withinor in proximity to (< 100 m) muskeg habitat,although dispersal to isolated locations withina variety of habitat types also appears to bea calving strategy (Alberta Natural ResourcesService unpubl. data).

Functional habitat will include both appropriateseasonal ranges and suitable paths of travelbetween them. During winter, the caribou pre-fers to follow the easiest path of travel andoften moves along frozen rivers, lakes, orwetlands (Darby and Pruitt 1984; Duquette1985). Caribou generally have strong fidelityto their traditional travel routes between sum-mer and winter ranges. Typical distances be-tween summer and winter ranges are lessthen 12 km for Woodland Caribou of the LittleSmoky herd (Brown and Hobson 1998).

2.6 Sensitivity to HumanDisturbance

When experiencing perpetual disturbance byhuman activity, the caribou may avoid orabandon optimal or traditional habitats in favourof less suitable ones and may even reducethe home range size of the herd (Bradshawet al. 1997). Noise disturbance has been foundto disrupt the feeding behaviour of the cari-bou. Though it may return in time to thepreviously occupied location, it has been ob-served to be driven away by loud sounds(Bradshaw et al. 1997). Research has shownthat caribou home ranges, particularly thecalving grounds are at maximum distance fromroads and human population centres(Cumming 1992).

Road and railway accidents are importantcauses of mortality and can severely impacta population that is already of low density(Cumming 1992). Hunting of caribou is nolonger permitted in Alberta but poaching mayhave serious impacts on small isolated herds(Cumming 1992).



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3.0 MODEL

3.1 Envirogram

It will be necessary to create three separatemodels for Woodland Caribou since the ani-mals require significantly different habitat ele-ments during the spring/summer (called sum-mer below), rutting/calving (called reproduc-tion), and severe winter seasons (called win-ter below).

Three elements have been identified as criti-cal components of Woodland Caribou habitatduring all seasons – the ability to obtain ap-propriate food resources; to minimise distur-bance by human activity; and to find suitablecover from inclement environmental condi-tions (Figures 2 to 4). The forest featuresimportant to the animals’ success in achiev-ing these endeavours are shown in theenvirograms below.

Summer Habitat

During summer, caribou take advantage ofample lichen, herbaceous vegetation, andshrub resources as forage. Additionally, cari-bou may benefit from the option of movinginto coniferous forests with a relatively closedcanopy for shelter from environmental con-ditions. Habitat suitability is also influenced byproximity to roads (Figure 2).

Winter Habitat

During winter, plentiful lichens and ground veg-etation are necessary. Since forbs and de-ciduous shrubs are not as readily available inlate fall and early winter, the caribou feedmore heavily on lichens with supplements ofsedges. Cover requirements are similar year-round (variables are identical to those shownabove (Figure 3).

Reproductive Habitat

While calving, female caribou prefer to locatethemselves in proximity to muskeg habitatsurrounded by ample food resources.

3.2 Application Boundaries

Season: Three separate modelshave been created forWoodland Caribou habitat –summer, winter, and repro-duction.

Habitat Area: Home range size used forhome range smoothing is2,400 ha for summer habi-tat and 16,800 ha for win-ter habitat.

Model Output: The model assigns seasonalSI values to each 25 m pixelof forested habitat.

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Figure 3. Envirogram of Woodland Caribou winter habitat based on available infor-mation for HSM development.

Figure 2. Envirogram of Woodland Caribou summer habitat based on available infor-mation for HSM development.

Specific Uses General Uses Habitat Use Species

WoodlandCaribou(summer)

Forb cover (%)

Sedge cover (%)

Ground lichen cover(%)

Groundvegetation

Stand age (mature toold)

Lichen availability

Canopy closure(< 50%)

Food resources

Protection frompoachers and

accidents

Tree speciescomposition

Distance from road(m)

Shrub cover (%)

Protection fromenvironmental

conditions

Cover

Arboreal lichen cover


WoodlandCaribou

(winter)

Sedge cover (%)


Groundvegetation

Stand age (mature toold)

Lichen availability

Canopy closure(< 50%)

Food resources


accidents

Tree speciescomposition


Protection fromenvironmental

conditions

Cover




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Figure 4. Envirogram of Woodland Caribou reproductive habitat based on availableinformation for HSM development.


WoodlandCaribou

(reproduction)

Sedge cover (%)

Forb cover (%)


Groundvegetation

Lichen availability

Food resources


accidents

Muskeg


Shrub cover (%)

Cover


Suitable covercharacteristics

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3.3 Model Description

The HSMs for Woodland Caribou seasonalhabitats follow the structures described in theenvirograms (Figures 5 to 7). As each ele-ment is critical and needed at the same time,no compensation is allowed between the sea-sonal elements. Distance from roads is usedas a part of the cover habitat suitability equa-tions for all seasons.

Summer Habitat

The SIfood during summer, SIfood(summer), con-sists of the variables lichen, forb, shrub, andsedge cover. SIcover is the same in both sum-mer and winter. It includes the variables standage, tree species composition, and canopyclosure. Suitability is reduced with proximityto roads (Figure 5).

Figure 5. HSM structure for Woodland Caribou summer habitat in Millar Western’sFMA area.

Winter Habitat

SIfood for winter consists of variables indicat-ing the percentage of forest floor coveredwith lichens, the coverage of arboreal lichens,and sedge cover (Figure 6).

Reproductive Habitat

SIfood for the calving season is identical to thatof summer habitat. SIcover (reproduction) includesthe variables of presence of muskeg and dis-tance from roads (Figure 7).

Variable Description Variables Suitability Index Equation

Lichen cover (%)

Forb cover (%)

Shrub cover (%)

Sedge cover (%)

Stand age (years)

Canopy closure (%)

Tree species composition

Distance from roads (m)

Sf1

Sf4

Sf3

Sf2

SIfood(summer) = Sf1 + Sf2 + Sf3 + Sf4 + Sf5;

where SIfood(summer) ≤≤≤≤ 1

SIcover = (Sc1 * Sc2 * Sc3)1/3 - [0.5(1-Sh1)];

where SIcover ≥≥≥≥ 0

Sh1

Sc1

Sc2

Sc3

Arboreal lichen cover Sf5



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Figure 6. HSM structure for Woodland Caribou winter habitat in Millar Western’s FMAarea.

Figure 7. HSM structure for Woodland Caribou reproduction habitat in MillarWestern’s FMA area.


Lichen cover (%)

Sedge cover (%)

Stand age (years)

Canopy closure (%)

Tree species composition


Sf1

Sf3

SIfood(winter)= Sf1 + 0.25Sf3 + Sf5;

where SIfood(winter) ≤≤≤≤ 1

SIcover = (Sc1 * Sc2 * Sc3)1/3 - [0.5(1-Sh1)];

where SIcover ≥≥≥≥ 0

Sh1

Sc1

Sc2

Sc3



Lichen cover (%)

Forb cover (%)

Shrub cover (%)

Sedge cover (%)

Presence of muskeg


Sf1

Sf4

Sf3

Sf2

SIfood(summer) = Sf1 + Sf2 + Sf3 + Sf4 + Sf5;

where SIfood(summer) ≤≤≤≤ 1

SIcover(reproduction) = Sc4 - [0.5(1-Sh1)];

where SIcover(reproduction) ≥≥≥≥ 0Sh1

Sc4


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Figure 8. Woodland Caribou foraging habitat suitability in relation to lichen coverwithin Millar Western’s FMA area.

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10 12

Lichen cover (%)

Sf1

3.4 Habitat Variable SIs

Food

Foods used by the Woodland Caribou through-out the year include ground lichens (Sf1),shrubs (Sf2), sedges (Sf3), forbs (Sf4), andarboreal lichens (Sf5). Suitability increases lin-early with greater representation of all of thesevegetation types. Maximum suitability isreached at 10% for ground lichens (Figure8), 25% for shrubs (Figure 9), 10% for sedges(Figure 10), and 15% for forbs (Figure 11).In addition, a stand that has been given anarboreal lichen cover rating of high is consid-ered optimal caribou foraging habitat (Figure12).

Cover

Preferred forest cover is provided by standsof mature to old age (Sc1, Figure 13). Canopyclosure of 20 to 50% promotes optimal lichengrowth (Sc2, Figure 14). Figure 15 shows thatoptimal cover is provided by relatively purepine or spruce stands (Sc3). Cover for thecalving season is provided by muskeg envi-ronments. For variable Sc4, all pixels repre-senting muskeg habitat receive a suitabilityrating of 1 while all others are rated 0. Coverhabitat suitability is optimal at distances greaterthan 500 m from roads (Sh1, Figure 16).



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0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10 12

Sedge cover (%)

Sf3

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20 25 30

Shrub cover (%)

Sf2

Figure 9. Woodland Caribou foraging habitat suitability in relation to shrub coverwithin Millar Western’s FMA area. Weighting: 0 - 3 m = 1, > 3 m = 0.2.

Figure 10. Woodland Caribou foraging habitat suitability in relation to sedgecover within Millar Western’s FMA area.

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0

0.2

0.4

0.6

0.8

1

Low Medium High


Sf5

Figure 12. Woodland Caribou foraging habitat suitability in relation to arboreallichen cover within Millar Western’s FMA area.

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20

Forb cover (%)

Sf4

Figure 11. Woodland Caribou foraging habitat suitability in relation to forbcover within Millar Western’s FMA area.



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0

0.2

0.4

0.6

0.8

1

Clearcut Regenerating Young Immature Mature Old

Developmental stage

Sc1

0

0.2

0.4

0.6

0.8

1

0 10 20 30 40 50 60 70 80 90 100

Canopy closure (%)

Sc2

Figure 13. Woodland Caribou cover habitat suitability in relation to develop-mental stage within Millar Western’s FMA area.

Figure 14. Woodland Caribou cover habitat suitability in relation to tree spe-cies composition within Millar Western’s FMA area.

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Figure 16. Woodland Caribou hiding cover suitability in relation to proximity toroad within Millar Western’s FMA area.

0

0.2

0.4

0.6

0.8

1

0 100 200 300 400 500 600

Distance to roads (m)

Sh1

0

0.2

0.4

0.6

0.8

1

0 25 50 75 100

Spruce or pine (%)

Sc3

Figure 15. Woodland Caribou cover habitat suitability in relation to tree spe-cies composition within Millar Western’s FMA area.



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3.5 Computation

Our goal is to create HSMs that allow theuser to identify the potential impacts of pro-posed forest management strategies on cari-bou habitat. The Woodland Caribou has dif-ferent habitat requirements during each sea-son. For this reason, three HSMs have beendeveloped – summer, winter, and reproduc-tion. The results of the SIs for these sea-sons are displayed separately.

Prior to the assessment of the quality of apotential home range as seasonal habitat, theseasonal SIs for food and cover are evalu-ated for each pixel using the following equa-tions. Cover habitat suitability is reduced byproximity to roads. To take this into account,all roads are buffered to a distance of 500 m.The suitability ratings of all pixels within thebuffer are reduced according to the distance-dependent relationship shown in Figure 16. Allpixels outside of the buffer are given a suit-ability rating of 1 for this variable.

SIfood(summer) = Sf1 + Sf2 + Sf3 + Sf4 +Sf5 ;

where SIfood(summer) ≤ ≤ ≤ ≤ ≤ 1.

SIfood(winter) = Sf1 + 0.25Sf3 + Sf5 ;

where SIfood(winter) ≤ ≤ ≤ ≤ ≤ 1.

SIcover = (Sc1 * Sc2 * Sc3)1/3 – [0.5(1-

Sh1)];

where SIcover ≥≥≥≥≥ 0.

SIcover(reproduction) = Sc4 – [0.5(1-Sh1)];

where SIreproduction ≥≥≥≥≥ 0.

Caribou are thought to select both summerand winter habitat based on food supply.Therefore, the cover equation can be con-sidered a modifier of foraging habitat suitabil-ity. To take this into account, the summerand winter food equations are combined withthe cover equation in such a way that standsoffering suitable foraging opportunities are con-sidered slightly less suitable if they lack thedesired cover characteristics.

Adjusted SIfood(summer) = SIfood(summer) –[0.2(1-SIcover)];

where Adjusted SIfood(summer) ≥≥≥≥≥ 0.

Adjusted SIfood(winter) = SIfood(winter) –[0.2(1-SIcover)];

where Adjusted SIfood(winter) ≥≥≥≥≥ 0.

Female caribou with calves are most securewithin 100 m of muskeg habitat. Therefore,the suitability rating of food resources withinthis distance of muskeg should be improvedover that of more distant pixels. Similarly, thequality of cover habitat is enhanced by prox-imity to food resources. This can be ac-counted for using the following equations:

Adjusted SIfood(reproduction) =[SIfood(summer) * Window [Max

SIcover(reproduction)]1/2

100m]

Adjusted SIcover(reproduction) =[SIcover(reproduction) * Window [Max

SIfood(summer)]1/2

100m]

Summer

To assess the quality of each potential homerange as caribou summer habitat, the ad-justed SIfood(summer) ratings are averaged withina circular window of radius 2,775 m (2,419ha). The average values are applied to thecentre pixel as its SI rating. The circle thenmoves over 2,775 m (one full radius) andthe averages are again taken and applied tothe centre pixel.

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Winter

The suitability of a potential range as winterhabitat is assessed using the adjustedSIfood(winter) calculation. Food suitability ratingsare averaged within a circular window of ra-dius 7,300 m (16,742 ha) and average val-ues are applied to the centre pixel. The win-dow moves in such a way that its centres arelocated 7,300 m (one full radius) apart. Thismoving circle need not be centred at the samepoint as the summer range since migrationfrom summer to mild winter range is a com-mon behaviour of the caribou.

Reproduction

The suitability ratings for foraging and coverhabitats for the reproductive season are notsmoothed. Female caribou may elect to mi-grate long distances to utilise a preferred calv-ing site. Smoothing reproduction suitability rat-ings would cause the precise locations of thepotential calving sites to be lost.



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4.0 EXTERNAL REVISION

On June 16, 1999, Christoff Rohner, post-doctorate fellow working at the University ofAlberta on Woodland Caribou research, pro-vided a review of an early draft version ofthe caribou HSM. The following alteration wasmade based on his advice:

1) Rohner did not believe that rock outcropsor barren lands were important componentsof the Woodland Caribou predator evasionstrategy in west-central Alberta. This por-tion of the model was, therefore, removed.Subsequently, all other reviewers providedthe same comment.

Arlen Todd, wildlife biologist with Alberta Envi-ronment, Fisheries and Wildlife ManagementDivision in Whitecourt, Alberta provided histhoughts on the Woodland Caribou HSM onJune 23, 1999.

1) Along with editorial comments, Todd statedthat we had under-estimated the capabil-ity of the caribou to function in snow.

2) Though mentioned in the literature reviewthat caribou use pure spruce stands, themodel considered only pure pine, spruce/pine mixedwoods, and treed muskeg asappropriate forest cover habitats. This over-sight was corrected.

On June 24, 1999, the comments of KentBrown, caribou researcher in Alberta, weresent via email to KBM. The followingsummarises his comments:

1) We had indicated in the review that cari-bou may group together to lessen preda-tion pressure. Brown has informed us thatthe caribou in that area do not performthis behaviour.

2) The Selkirk caribou in Idaho are the mostresearched of all North American caribou.We had incorporated some habitat selec-tion data from this research into the modelfor caribou of west-central Alberta. Brownpointed out that the ecology of these two

herds is very different and this compari-son is not appropriate. This idea was con-firmed by the next reviewers, Kirby Smithand Jan Ficht (nee Edmonds).

3) Though the literature review stated thatlichens are most productive in forests withcanopy closure less than 50%, the signwas reversed and for modelling purposes,they were said to be most productive inrelatively closed canopy forests. This errorwas corrected.

4) Brown stated that the lower critical tem-perature of a caribou is -30 to -35 oC.Therefore, they are not seriously influencedby temperature in Alberta.

Kirby Smith and Jan Ficht (nee Edmonds) ofthe Alberta Natural Resources Service inEdson, Alberta reviewed a version of the cari-bou HSM and provided comments on June30, 1999. Through these comments, the fol-lowing changes were made:

1) These two researchers stated that com-pared to other members of the deer fam-ily, caribou are well adapted to snow. Al-though they prefer to move through shal-lower and less crusted snow, they are notcompletely restricted by the presence ofdeep snow. In addition, caribou can smelllichens and crater through up to 100 cmof snow. Where ground lichens are un-available, they will turn to arboreal lichens.

2) We had written that caribou would seekmuskeg environments for predator avoid-ance since their abilities to detect incomingpredators are heightened in open environ-ments. Ficht and Smith stated that moreimportantly, caribou in west-central Albertadisperse into very low density populationstructures. This allows them to best avoidwolf predation.

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3) The importance of the food items readilyavailable during green-up in small clearings,muskegs, south-facing slopes, etc. wasunderstated.

4) Updated home range size estimates fromthe unpublished data of Alberta NaturalResources Service were provided by Fichtand Smith.

5) Though it had been previously suggestedthat caribou will move into ‘late winter cover’only during severe winter conditions, theunpublished data of the Natural ResourcesService indicate that mature coniferous for-est is the most commonly used habitatregardless of winter snow conditions.



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5.0 LITERATURE CITED

Boonstra, R. and A.R.E. Sinclair. 1984. Distri-bution and habitat use of caribou, Rangifertarandus caribou and moose, Alces alcesandersoni, in the Spatsizi Plateau Wilder-ness Area, British Columbia. Can. Field Nat.98: 12-21.

Bradshaw, C.J.A., D.M. Hebert, A.B. Rippinand S. Boutin. 1995. Winter peatland habi-tat selection by Woodland Caribou in north-eastern Alberta. Can. J. Zool. 73: 1567-1574.

Brown, W.K. Research Subcommittee of theWest-central Alberta Caribou StandingCommitte. 1999. Personal Communication.

Brown, W.K. and D.P. Hobson. 1998. Caribouin west-central Alberta – Information re-view and synthesis. Terrestrial and AquaticEnvironmental Managers Ltd. Unpubl. Rep.prep. for the Research Subcommittee ofthe West-central Alberta caribou standingcommittee, Calgary, AB.

Cumming, H.G. 1992. Woodland Caribou:Facts for forest managers. For. Chron.68(4): 481-491.

Darby, W.R. and W.O. Pruitt Jr. 1984. Habitatuse, movements and grouping behaviourof Woodland Caribou, Rangifer taranduscaribou, in southeastern Manitoba. Can.Field Nat. 98(2): 184-190.

Duquette, L.S. 1985. Draft: Habitat manage-ment guidelines for Woodland Caribou.

Edmonds, J.E. 1988. Population status, dis-tribution and movements of Woodland Cari-bou in west-central Alberta. J. Zool. 66:817-826.

Harris, A. 1996. Post-logging regeneration ofreindeer lichens (Cladina spp.) as relatedto Woodland Caribou winter habitat. Natu-ral Resources Canada, Canadian ForestService, OMNR, 33 pp.NWST TechnicalReport TR-69.

Rettie, W.J. and F. Messier. 1998. Dynamicsof Woodland Caribou populations at thesouthern limit of their range inSaskatchewan. Can. J. Zool. 76: 251-259.

Rettie, W.J., J.W. Sheard and F. Messier. 1997.Identification and description of forestedvegetation communities available to Wood-land Caribou: relating wildlife habitat to for-est cover data. For. Ecol. and Manage.93: 245-260.

Servheen, G. and L.J. Lyon. 1989. Habitatuse by Woodland Caribou in the SelkirkMountains. J. Wildl. Manage. 53(1): 230-237.

Smith, K.G. Area Wildlife Biologist, Whitecourt,AB. 1999. Personal communication.

Smith, H.C. 1993. Alberta Mammals: An At-las and Guide. Provincial Museum ofAlberta, Edmonton.

Smith, K.G., E.J. Frichot, D. Hobson and D.Hervieux. 1998. Woodland Caribou distri-bution on winter range in relation to clear-cut logging in west-central Alberta – Man-agement implications. Foothills Model For-est Tech. Rep.

Stuart-Smith, A.K., C.J.A. Bradshaw, S.Boutin, D.M. Hebert and A.B. Rippin. 1997.Woodland Caribou relative to landscapepatterns in northeastern Alberta. J. Wildl.Manage. 61: 622-633.

Thomas, D.C., E.J. Edmonds, and W.K.Brown. 1996. The diet of Woodland Cari-bou populations in west-central Alberta.Ranifer Spec. Iss. 9: 337-342.

Van Tighem, K. 1990. Grey ghosts. NatureCanada Fall: 22-27.

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