,

A Survey of the Amphibians and Reptiles of the North Platte National Wildlife Refuge

John B. Iverson 25 November 2001

[in fulfillment of USFWS purchase order #6451 0-1-M008A]

Abstract: During the spring and summer of 2000 and 200 l , we surveyed the amphibians and reptiles on all of the seven units of the North Platte National Wildife Refuge and adjacent properties, using cover board arrays, drift fence arrays, fyke net trapping, frog call surveys, visual (binocular) surveys, road-cruising, and time-constrained walking surveys. We recorded four species of amphibians and twelve species of reptiles (at 51 locations) on the Refuge: one salamander, one toad, two frogs, four turtles, three lizards, and five snakes. An additional49 localities near the Refuge added only two species (one lizard and one snake) to the faunal list; these two species may be occasional residents of the Refuge. Another secretive species (a snake) was not captured during any of our field work, but is known in the county and likely also inhabits the Refuge. Four other species (1 toad, 3 lizards) have never been collected in Scotts Bluff County (including during our survey), but may occur as relicts in that county, and might be very rare inhabitants of the Refuge. The primary goal of active management of the Refuge for herps should be to increase the number of ephemeral wetlands.

The reptiles and amphibians of western Nebraska have been. fairly well surveyed on a regional scale (Hudson, 1942; Lynch, 1985), although most collections made in Scotts Bluff County have been incidental captures only. We initiated a survey of the amphibians and reptiles of the various units of the North Platte National Wildlife Refuge in the spring of 2000 and continued our survey through the end of May 200 l.

Methods

[was assisted in my field surveys in 2001 by Cameron Young (University of Georgia), David Young (West Inc., Cheyenne), Kirsten Hines (Florida International University), Colin Meeks (Earlham College), Steve Dinkelacker (Miami University of Ohio), and Saul Nava (University of Texas at El Paso). We spent 55 person-days on or immediately adjacent to Refuge property during the course of our work, on the following dates: 15-16 April, 23 April, 5-6 May, ll May, 17 May, 22 June, and 30 September 2000, and 26 April, 2 May, and 20-28 May 2001. We employed each of the following methods during our survey work:

Cover board arrays

During May of 2000 we distributed 103 total wooden (ca. 36" x 48") or metal (ca. 24" x 48") coverboards across all Refuge units (Fig. 1). These coverboards were checked during each subsequent visit as well as every other day during late May of 200 l. The coverboards remain in place to date and we anticipate continuing to check them in 2002 at our expense, in the hope of obtaining new records for the Refuge.

Fig. 1. Locations of drift fences (stars), coverboard arrays (xxx), and fyke net sites (F) on the North Platte NWR.

Drift fence arrays

Between 20 and 22 May 2001, we constructed 8 drift fence arrays, consisting of 50' of aluminum flashing buried in the ground in optimal herp habitat, with shaded wire funnel (live) traps placed on both sides at each end and along the middle of the fence. These fences were deployed until 28 May 2001 (50 total fence-days). To our surprise (given the success we have had with fences on the Crescent Lake NWR), we did not collect a single herp in these drift fences. This certainly reflects the low densities of herps found on this Refuge:

Fyke net trapping for turtles

Fyke nets consisting of 50' x 6' 1" mesh leads stretched between two carp-baited 3' diameter hoop (funnel) traps were deployed at the seven sites with the best turtle habitat on Winters Creek Lake

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and Lake Minatare in May of2001. Lack of shoreline habitat precluded our trapping in Lake Alice. We captured only six total turtles in 16 trap days (0.375/day), which is about l/30th the typical capture rate ( 10/day) in lakes at the same latitude in northern Indiana (Iverson, unpublished). The extremely )ow density of aquatic turtles on the Refuge is obvious.

Frog call surveys

During every visit to the Refuge we made note of locations and intensities of calling frogs and toads.

Visual (binocular) surveys

We regularly surveyed shorelines and emergent logs for the presence of basking turtles (and snakes). Normally a reliable method for verifying the presence of species such as the painted turtle, we observed basking turtles only at Stateline Island (west) and Winters Creek Lake (west).

Road-cruising

In addition to casual observations made of herps on the road during our regular field work, we also purposely drove the road at dusk on warm nights on several occasions in an effort to intercept herps exploiting the low light levels and warm temperatures. We drove approximately 1900 miles in Scotts Bluff County in May of 2001, either on or between the Refuge Units.

Time-constrained walking surveys

We spent considerable time surveying the ground as we walked to check coverboards, drift fences, and fyke nets. However, our most successful method by far involved timed walking surveys (usually four of us walking abreast, separated by 5 to 20 meters, scanning the ground, and turning any cover material on the ground, such as rocks, tree branches, or even trash). We used time­constrained surveys on every Refuge unit:

Stateline west (of Hwy) 21May 3 person-hours (5 snakes) 23May 9 person-hours (7 turtles) 25May 1 person-hour (zero)

Stateline east (of Hwy) 21May 6 person-hours (3 dead turtles) 25May 2 person-hours (zero)

Lake Alice 22May 6 person-hours (zero) 25May 10 person-hours (2lizards, 1 toad)

Winters Creek, west of Lake 21May 3 person-hours (zero) 24May 3 person-hours (zero)

Winters Creek, east of Lake 25May 2 person-hours (1 snake) Central Sage (NW Minatare) 21May 2 person-hours (zero)

23May 5 person-hours ( 1 box turtle) Lake Minatare (west unit) 24May 4 person-hours (1 snake, 1 lizard, 1 toad) Lake Minatare(eastunit) 22May 4 person-hours (zero)

26May 2 person-hours (zero) Lake Minatare (north cove) 21 May 2 person-hours (zero)

24May 2 person-hours (zero) North of Lake Alice 22May l person-hour (two box turtles)

(off refuge) 26May 12 person-hours (1 snake, 6 lizards, 1 turtle) 27May 20 person-hours ( 4 turtles, 6 snakes, 11

lizards, 1 toad)

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Species Lists

Only 16 of the 25 total possible species of reptiles and amphibians were recorded on the Refuge during our field work. Those species are in the following annotated lists which provide locations on and/or off the Refuge (all Scotts Bluff County, unless otherwise indicated). Precise latitudes/longitudes were obtained whenever possible via GPS; others (preceded by "ca." in the lists) were estimated using Street AtlasTM software.

Three lists of species are provided: 1) those species verified to occur on the Refuge (16); 2) those recorded immediately adjacent to, but not on the Refuge (2); and 3) those not recorded from the Refuge or nearby the Refuge, but expected to occur in the area (7). Maps of the known distributions of each species in Nebraska (from Lynch, 1985) and on the Refuge (based on our work) are provided (previous records marked with solid circles and new records from our work mrked with bold x's).

Species of reptiles and amphibians captured on the North Platte National Wildlife Refuge

Salamanders

Ambystoma tigrinum mavortium Barred Tiger salamander

On Refuge: Ephemeral wetland south of Winters Creek Lake (larvae; ca. 41 o 56.94N, 103° 31.26W)

22June 2000 Off Refuge: none

The Tiger Salamander is found throughout the State, although no previous records existed for Scotts Bluff County (Lynch, 1985). A small population breeds in the wetland south of Winter Creek Lake, but the location of adult (terrestrial) habitat is unclear given the proximity of the canal to the Southwest and the lake to the north. This wetland is the single most productive (and diverse) habitat for amphibians on the Refuge and should be left intact. However, the construction of additional ephemeral ponds (see General Recommendations) on the Refuge (and even the introduction of salamander larvae to them) would create insurance should something catastrophic happen to the current wetland. For tiger salamanders, the most optimum locations for placement of more ponds would be in the east Winters Creek unit, the central Sage unit north of Minatare and the low areas that already exist on the Stateline Unit.

Frogs and toads

Bufo woodhousii woodhousii Woodhouse's Toad

On Refuge: Minatare west, along Lake inland from dumping station (ca. 41° 55.97N, 103° 31.08W to

41° 56.19N, 103° 31.17W) 5 May 2000 Wetland SEofWinters Creek Lake (calling; ca. 41° 56.94N, 103° 31.26W) 5 May 2000 Winters Creek west, flooded field south of canal (calling; ca. 41 o 57.34N, 103° 32.03W)

5May2000

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Wetland SEofWinters Creek Lake (tadpoles; ca. 41° .56.94N, 103° 3l.26W) 22June 2000 Minatare west just west of CB 8 (ca. 41° 55.47N, 103° 30.90W) 24 May 2001 Minatare north, all along lake shoreline (ca. 41 o 56.29N, 103° 31.08W to 41° 5632N,

103° 31.01W) 26 May 2001 South border of Lake Alice south unit (41 o 58.792N, 103° 36.367) 25 May 2001

Off Refuge: Pools just south of Minatare west (2 toads; ca. 41° 55.31N, 103° 30.72W) 5 May 2000 North of Lake Alice at windmill at corral (ca. 41° 59.66N, 103° 35.75W) 22 May 2001 North of Lake Alice (42° 00.227N, 103° 36.081W) 27 May 2001 0.3 mi NW of Nebraska Fish and Game office, N of Minatare (41 o .56.143N, 103° 30.494W)

28May200l

This toad occurs across the entire state of Nebraska, having been recorded from nearly every county (Lynch, 1985). They can breed in temperate (ephemeral) wetlands as well as along the edges of permanent bodies of water. We recorded calling males all along the northwest margins of Lake Minatare, in the wetland southeast of Winters Creek Lake, and west of Winters Creek Lake. Good populations exist on the Refuge, but numbers could be enhanced with the construction of ephemeral wetlands designed to enhance tiger salamander populations (see Ambystoma tigrinum and General Recommendations).

Pseudacris t riseriata macula1a Boreal Chorus Frog

On Refuge: Northwest shore Lake Minatare (calling males; ca. 41 o 55.97N, 103 o 3l.08W) 23 April 2000 Wetland SEofWinters Creek Lake (calling males; ca 41° 56.94N, 103°31.26W) 23 April 2000 Wetland SE of Winters Creek Lake (calling males; ca. 41° .56.94N, 103° 31.26W) 5 May 2000 Winters Creek west, flooded field south of canal (calling males; ca. 41 o 57.34N, 103° 32.03W)

5May2000 Winters Creek east, southeast shore of Lake (calling males; ca. 41 o 57.11N, 103° 31.13W)

5May2000 Stateline west, cattail ditch on west of Hwy near gate (calling males; ca. 41 o 59.39N,

104° 02.86W) 22 June 2000 Winters Creek west, ponds near storage building (calling males; ca. 41 o 57.45N, 103° 31.93W)

24May 2001 Off Refuge: none

This tiny frog also occurs throughout the State, but is known from only a single locality in Scotts Bluff County (at Scottsbluff; Lynch, 1985). It breeds in marshes, ephemeral ponds, and in roadside ditches. We recorded calling males in April- June (in particular on warm nights, but also on overcast days), primarily between Lake Minatare and Winters Creek Lake. Breeding populations (where they occur) are substantial , but would benefit from the construction of additional ephemeral ponds (see Ambystoma tigrinum; General Recommendations).

Rana catesbiana Bullfrog

On Refuge: Stateline west in west pond (tadpoles and adult; 41° 59.341N, 104° 03.114W) 23 May 2001

Off Refuge: none

The natural range in Nebraska is uncertain since bullfrogs (adults and larvae) have been carried all over the state by fishermen as well as Game and Parks Commission personnel. Today they occur nearly throughout the state except for Sandhills regions distant from rivers. The only previous

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record for Scotts Bluff County is from 3 mi. SE of Henry (Hudson, 1942) near the North Platte River in the northwestern corner of the county (Lynch, 1985). We observed bullfrog tadpoles in abundance in the spring-fed pond at the west end of the west Stateline Unit Despite its occurrence at only one site on the Refuge, this "weedy" species requires no management.

Turtles

Che lydra serpent ina serpent ina Common Snapping Turtle

On Refuge: Stateline west, Platte River bank on north shore (predated nests, eggs retained (41 ° 5938N,

104° 03.09) 22 June 2000 Stateline east, east pond (3 dead; ca. 41° 59.06N, 104° 02.20W) 21 May 2001 Stateline west, west pond (2 animals; 41° 59.341N, 104° 03.114) 25 May 2001

Off Refuge: none

This distinctive turtle occurs throughout Nebraska, although no records are available for Scotts Bluff County (Lynch, 1985). The species can be found in nearly any body of water; they prefer permanent water but will migrate to temporary ponds to exploit food resources and warmer temperatures therein. We found snapping turtles to occur in the greatest concentration on the west Stateline unit. We also found three dead snappers in a small, apparently permanent pool at the east end ofthe Stateline unit. We suspect that those turtles were winter-kilJed, as the maximum depth of the pond appeared to be only a little over a half meter. Depredated snapping turtle nests were also common along the south bank of the North Platte River (north boundary of the west Stateline unit). Surprisingly no snapping turtles were captured on any of the other NPNWR units, perhaps because of the high population of nest predators (raccoons), the abundance offishennan (who typically kill them), the herds of grazing cattle that trample and collapse nests (e.g., at Lake Alice), and the general dirth of shoreline emergent vegetation due to water level fluctuations (eliminating developmental habitat). Snapping turtles most certainly occur in other units but their numbers must be very low.

Chrysemys picta bellii Western Painted Turtle

On Refuge: Winters Creek west in canal (2 hatchlings; ca. 41° 57.39N, 103° 32.01W) 21 May 2001 Winters Creek west in ponds east of storage building (5 adults; ca. 41 o 57.44N, 103° 31.93W)

24May2001 Stateline west, in west pond (4 adults; 41 o 59.341N, 104° 03.114W) 25 May 2001

Off Refuge: none

Although the painted turtle certainly occurs statewide, no previous records are available for Scotts Bluff or Morrill Counties (Lynch, 1985). This species prefers permanent water with abundant shoreline vegetation (emergent and submergent) and hence is not common anywhere on the Refuge. We did capture specimens in the west pond of the west Stateline Unit as well as in the backwaters associated with the western shore of Winters Creek Lake. The presence of this species is generally easy to confirm by using binoculars to scan logs near the shoreline for basking individuals. Such surveys in Lake Alice, Lake Minatare, and Winters Creek Lake resulted in no additional sightings. The low density of this species on the Refuge is certainly due to the general lack of appropriate shoreline habitats.

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Terrapene ornata ornata Ornate Box Turtle

On Refuge: Central Sage unit, south quarter (ca. 41° 56.48N, 103° 30.70W) 23 May 2001 100 meters E of entrance to Lake Alice on Refuge boundary (41° 58.624N, 103° 35.819W)

27 May 2001 Off Refuge:

1.5 mi. E, 4.8 mi. N Baxter (41 o 57.182' N, 103° 26.424'W) 22 May 2001 Just north of Lake Alice north unit (ca. 41° 59.47N, 103° 35.81W) 22 May 2001 South side of bluffs north of Lake Alice (41 ° 59.575N, 103° 35.502W) 26 May 2001 Just north of Lake Alice north unit (41° 59.702N, 103° 35.885W) 27 May 2001 Just north of Lake Alice north unit (41 ° 59.860N, 103° 35.905W) 27 May 2001 Just north of Lake Alice north unit (41 o 59.949N, 103° 35.997W) 27 May 2001 Just north of Lake Alice north unit (41 o 59.742N, 103° 35.860W) 27 May 2001

This terrestrial turtle occurs nearly statewise, except in the extreme eastern and northeastern parts of the State. No previous records are available for Scotts Bluff County, although this species is known from very near the eastern edge of that county in the North Platte River Valley in Morrill County (Lynch, 1985). Box turtles were located during walking transects north and south of Lake Alice, and in the central Minatare Lake unit, but not by other means (drift fences, road cruising, etc.). Populations on the Refuge are clearly very reduced, probably because of the small size of most of the habitats (relative to the large activity range of these turtles) as well as the many roads and canals that separate shoreline habitats from upland habitats (resulting in roadkills). The best current habitat on the Refuge lies in the Central Sage Unit north of Lake Minatare. Production here would likely increase if temporary ponds were created in the drainage valleys of the uplands there. These ponds would allow turtles to remain within the unit to obtain free-standing water, rather than attempt to make the hazardous migration to Lake Minatare.

Apalone spinifera hartwegi Western Spiny Softshell Turtle

On Refuge: Stateline east, North Platte River, just below (east) Hwy bridge (ca. 41° 59.47N, 104° 02.82W)

22June 2000 Stateline west, North Platte River, 200 meters E of Wyoming border (3 juveniles and 1 adult

female; ca. 41° 59.43N, 104° 03.04W) 23 May 2001 Stateline west, North Platte River, 100 meters E. of Wyoming border(female; ca. 41° 59.41N,

104° 03.11W) 23 May 2001 Stateline west, North Platte River, 10 meters E. of Wyoming border (juvenile; ca. 41 o 59.40N,

104° 03.17W) 23 May 2001 Off Refuge:

Wyoming, Goshen County, ca. 75 meters above coffer dam (juvenile and adult male; ca. 41 o 59.38N, 104° 03.20W) 23 May 2001

This species is associated primarily with rivers and streams in eastern and southern Nebraska. The nearest records to the NPNWR are from along the North Platte River in Garden County (Lynch, 1985). We found evidence of softshells only at the Stateline Unit, where they were abundant in the main channel of the North Platte River that forms the north boundary of that Unit. In five person-hours in May 2001, we coJlected seven individuals by hand along the shorelines of the river as they lay buried in substrate 5 to 50 em below the water surface. Depredated nests were also found along the same northern boundary on the western Stateline unit. It is possible that softshells also occur along canals or in the lakes of the eastern Refuge units, but if so, their

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numbers must be very low. Because they regularly bask on sunny days, their presence is normally easily confirmed with binocular surveys.

Lizards

Holbrookia maculata maculata Northern Earless Lizard

On Refuge: Lake Alice north. on fence post (41 o 59300N, 103° 36.061W) 25 May 2001

Off Refuge: none

This species occurs primarily on sandy soils with sparse vegetation and in Nebraska is distributed primarily from the Platte River Valley northward. A single previous record is available for Scotts BLuff County (7 mi. northeast of Mitchell; Hudson, 1942; Lynch, 1985). Despite intensive walking surveys of the Refuge and adjacent habitats, we collected only a single freshly killed individual from atop a fence post north of Lake Alice. The lizard had apparently been predated by a bird (e.g., a shrike or kingbird) and left on the post. The sandy environment around the shoreline of Lake Alice would seem to be optimal habitat for this lizard, yet we could not find a single live individual. Our only hypothesis for this is that the great (and rapid) fluctuations in water level may drown them in their nests, retreat burrows, and/or hibernation burrows.

Sceloporus undulatus garmani Northern Prairie Lizard

On Refuge: South shore of Lake Alice (41 ° 58.851N, 103° 36.229W) 22 June 2000 Minatare west, west of CB8 (ca. 41° 55.42N, 103° 30.80W) 24 May 2001 Lake Alice north, 50 meters W of canal crossover off NE comer Lake Alice along fenceline

(41° 59.170N, 103° 35.809W) 25 May 2001 Off Refuge:

North of Lake Alice at windmill at corral (ca. 41 o 59.66N, 103° 35.75W) 22 May 2001 North of Lake Alice, halfway between Lake and Bluffs (ca. 41 o 59.51N, 103° 35.76W)

22May2001 North of Lake Alice, base of bluffs (41° 59.62SN, 103° 35.33SW) 26 May 2001 North of Lake Alice, in rocky bluffs (41 ° 59.796N, 103° 35.308W) 26 May 2001 North of Lake Alice, in rocky bluffs (42° 00.060N, 103° 36.014W) 26 May 2001

This is perhaps the most common lizard in the western half of Nebraska (Lynch, 1985), frequently seen on fence posts, and on Sandhills in association with clumps of yucca. On the Refuge we found this species to be surprisingly rare.

Eumeces multivirgatus multivirgatus Northern Many-lined Skink

On Refuge: Minatare east (CB 6; 41 o 56.018N, 103° 28.265) 26 April 2001

Off Refuge: none

In Nebraska these very secretive lizards are known from a number of widely dispersed localities in the northern half of the state. No records are available from Scotts Bluff, Morrill, or Banner Counties. We captured only two specimens during our field work, both under the same cover board on the top of the ridge in the East Minatare Unit in April 2001. This species is to be

8

expected on every Refuge Unit, but it spends nearly all of its life underground. As an example of the difficulty there can be in capturing specimens of this species, 20 years of drift fence trapping on the CLNWR has produced only three specimens (all having fallen in pitfall traps).

Snakes

Co Iuber constrictor jlaviventris Eastern Yellow-bellied Racer

On Refuge: Winters Creek west, 100m south of storage building (ca. 41° 57.41N, 103° 32.00W)

11 May 2000 Minatare east, near CB aray (41 o 55.893N, 103° 28.350W) 20 May 2001 Stateline west (ca. 41 o 59.37N, 104° 02.95W) 21 May 2001 Minatare west, under CB 8 (ca. 41° 55.47N, 103° 30.86W) 24 May 2001

Off Refuge: 1.0 mi. N Hwy 26 on road to Lake Minatare Dam (ca. 41° 49.78N, 103° 30.07W) 11 May 2000 NW of Winters Creek Lake, on road between Little Lake Alice and Winters Creek west ( 41 o

57.634N, 103° 33.428W) 26 May 2001

This diurnal snake is a generalist and occurs in nearly every habitat in Nebraska except open water. However, it has been recorded at only one location in Scotts Bluff County (7 mi. NE of Morrill; Hudson, 1942; Lynch, 1985). This is the second most common snake on the Refuge and almost certainly exists on every unit.

Pituophis catenifer sayi Bull snake

On Refuge: Minatare west, Hwy at turnaround at parking area (ca. 41 o 56.04N, 103° 31.24W) 11 May 2000 Stateline west (ca. 41° 59.37N, 104° 02.95W) 21 May 2001 Stateline west (3 animals; ca. 41 o 59.38N, 104° 03.00W) 21 May 2001 Stateline west, west shore of pond (41 o 59.351N, 104° 03.123W) 23 May 2001 SW of Winters Creek Lake along canal between Lake and Canal (41 ° 57.092N, 103° 31.664W)

Off Refuge: Canal RoadoffSW comer Winters Creek Lake (ca. 41° 57.13N, 103° 31.83W) 21 May 2001 4.4 mi. W Mintle (41 ° 56.602N, 103° 45.909) 23 May 2001 Scottsbluff,jct. East 33rd Street and Sugar Factory Road (ca. 41 o 52.80N, 103° 38.20W)

23 May 2001 0.2 mi. N Hwy 26 (at Minatare) on road to Lake Minatare (ca. 41° 49.11N, 103° 29.83W)

23 May 2001 Sugar Factory Road, 3.7 mi. N Hwy 26(41° 55.103N, 103° 38.294) 24 May 2001 1.0 mi. SE Henry on Hwy 26 (41° 59.326N, 104° 01.903 25 May 2001 Just N Minatare west unit in NE Game and Parks campground (2 animals; 41° 56.451N,

103° 30.993W) 26 May 2001 Along Highline Canal, due east of Little Lake Alice (41° 58.064N, 103 33.865W) 26 May 2001 North of Lake Alice (41° 59.725N, 103° 35.WW) 27 May 2001

Ranging across the entire state of Nebraska, this is the largest and most commonly observed snake in western Nebraska, and is to be expected on every unit of the Refuge. Although no voucher records previously existed for Scotts Bluff County, we observed them frequently both on and off the Refuge, and even witnessed courtship on two occasions (21 and 26 May 2001).

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Thamnophis radix haydenii Western Plains Garter Snake

On Refuge: Winters creek west, canal (ca. 41° 57.38N, 103° 32.00W) 22 June 2000 Wetland SE of Winters Creek Lake (ca. 41° 56.94N, 103° 31.23W) 22June 2000 Winters Creek east near lake shore (ca. 41° 57.40N, 103° 31.39W) 25 May 2001 S. of canal off S. shore Winters Creek Lake (41 ° 56.969N, 103° 31.520W) 26 May 2001

Off Refuge:

This snake ranges across the entire state of Nebraska and is the most tolerant species of snake toward urbanization (often occurring in abundance in the middle of cities and towns). Three previous records are known from Scotts Bluff County (Hudson, 1942; Lynch, 1985) and despite our capturing them on only one Unit, the species no doubt occurs throughout the county and on every Refuge unit.

Thamnophis sirtalis parietalis Red-sided Garter Snake

On Refuge: Wetland SE of Winters Creek Lake (2 animals; ca. 41 o 56.95N, 103° 31.24W) 22 June 2000 State.Jine west, west bank of west pond (41 ° 59.351N, 104° 03.123W) 23 May 2001

Off Refuge: none

This snake is distributed across nearly the entire State, except perhaps for the extreme southwestem Panhandle. The species seems to be more closely tied to rivers and streams than the Plains garter snake. Three records are known from Scotts Bluff County (Lynch, 1985): two from along the North Platte River (near Scottsbluff and 3 mi. SE Henry) and one from 7 mi. NE Mitchell (Hudson, 1942). We obtained only two individuals of this usually common species, although it probably occurs on every Refuge Unit.

Crotalus viridis viridis Prairie Rattlesnake

On Refuge: Minatare East, 0.2 mi. south of end of pavement (ca. 41° 56.40N, 103° 28.23W) 5 May 2000 Minatare East, near middle of coverboard array (41° 55.893N, 103° 28.350W) 20 May 2001 Minatare East, 50' south of end of pavement (41 ° 56.492N, 103° 28.227W) 22 May 2001

Off Refuge: North of Lake Alice (41 o 59.82JN, 103° 35.905W) 27 May 2001 North of Lake Alice (42° 00.069N, 103° 35.973W) 27 May 2001 North of Lake Alice (42° 00.039N, 103° 35.973W) 27 May 2001 North of Lake Alice ( 42° 00. 1 96N, 103 o 36.065W) 27 May 2001 Sioux Co., north of Lake Alice (42° 00.302N, 103° 36.258W) 27 May 2001 North of Lake Alice (41 ° 59.900N, 103° 35.955W) 27 May 2001

The only poisonous snake in western Nebraska, this species was previously recorded in Scotts Bluff County from only a single locality (7 mi. NE Mitchell; Hudson, 1942; Lynch, 1985). The distribution of this species on the Refuge is determined in part by the proximity of adequate winter denning sites (e.g., prairie dog towns, or rocky outcrops with deep fizzures). We found them most commonly on the East Minatare Unit (because of the abandoned prairie dog burrow system there) and north of Lake Alice (because of the rocky ridge to the north). However, rattlesnakes will venture miles from their hibemacula and hence are probably occasional inhabitants of nearly

10

every unit. On most units numbers are no doubt much lower than they were historically (i.e. before humans and vehicles killed them so regularly).

Additional species of reptiles and amphibians recorded immediately adjacent to but not on the

North Platte National Wildlife Refuge (i.e., potential Refuge residents)

Lizards

Sceloporus graciosus graciosus

On Refuge: none Off Refuge:

Northern Sagebrush Lizard

North of Lake Alice, on rocky bluffs (3 animals; 41 o 59.625N, 103° 35.335W) 22 May 2001 North of Lake Alice, on rocky bluffs (41° 59.796N, 103° 35.308W) 26 May 2001 North of Lake Alice, on rocky bluffs (41° 59.786N, 103° 35.333W) 26 May 2001 North of Lake Alice, on rocky bluffs (41° 59.989N, 103° 35.164W) 26 May 2001 North of Lake Alice, on rocky bluffs (41 o 59.981N, 103° 35.076W) 26 May 2001 North of Lake Alice, on rocky bluffs (2 animals; 42° 00.094N, 103° 36.013W) 27 May 2001 North of Lake Alice, on rocky bluffs (42° 00.039N, 103° 35.973W) 27 May 2001 North of Lake Alice, on rocky bluffs (42° 00.240N, 103° 36.093W) 27 May 2001 Sioux Co., North of Lake Alice, on rocky bluffs (42° 00.315N, 103° 36.264W) 27 May 2001 Sioux Co., North of Lake Alice, on rocky bluffs (2 animals; 42° 00.340N, 103° 36.230W)

27May2001 Sioux Co., North of Lake Alice, on rocky bluffs (42° 00.362N, 103° 36.313W) 27 May 2001 Sioux Co., North of Lake Alice, on rocky bluffs (42° 00.358N, 103° 36.271W) 27 May 2001 Sioux Co., North of Lake Alice, on rocky bluffs (42° 00.285N, 103° 36.240W) 27 May 2001 Morrill Co., 3 mi. N., 1.5 mi. W Broadwater (ca. 41 o 38.58N, 102° 52.78W) 24 May 2001

The sagebrush lizard was only added to the herpetofauna of the state in 1985 when Lynch reported specimens from two sites just north of Broadwater in Morrill County. Not only did we verify its presence in Morrill County, but we obtained many new records for Scotts Bluff County and even several new ones for Sioux County. Unfortunately, all of these new locations were just to the north of Refuge property. In Nebraska, the species seems to require rocky ridges, a habitat currently lacking on the Refuge. Any opportunity to expand the Refuge north of Lake Alice to and including the rocky bluffs there would make the greatest contribution to increasing herpetofaunal diversity of any other nearby property.

Snakes

Wmpropeltis triangulum mullistrata

On Refuge: none Off Refuge:

Pallid Milk Snake

North of Lake Alice, on rocky bluffs (41 o 59.992N, 103° 35.118W) 26 May 2001

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This very secretive and colorful species occurs throughout the state, although only a single record is available for the Panhandle in northwest Scotts Bluff County (2 mi. NE Morrill; Hudson, 1942; Lynch, 1985). We were unable to verify the existence of the species on the Refuge, although we did capture one in the rocky bluffs just north of Lake Alice, and it is probably a rare inhabitant of every Refuge unit.

Additional species of reptiles and amphibians not recorded on the North Platte National Wildlife Refuge

but expected to occur in the area

Frogs and Toads

Bufo cognatus Great Plains Toad

This species requires temporary bodies of water for breeding and is known from a single locality (at Morrill) in northwestern Scotts Bluff County (Hudson, 1942; Lynch, 1985). In general it is much Jess abundant than the Rocky Mountain Toad (Bufo woodhousii). The only possible breeding on the NPNWR would be in the wetland southeast of Winters Creek Lake or the few temporary ponds that form in the eastern interior of Stateline Island. The creation of additional temporary wetlands on the Refuge would benefit this species, although the species might have to be introduced from nearby populations.

Rana pipiens Northern Leopard Frog

In Nebraska, this species occurs in or north of the Platte River. One previous record from Scotts Bluff County is available, from 3 mi. SE of Henry (Hudson, 1942) along the Platte River in the northwestern part of the county (Lynch, 1985). This species breeds in both temporary and permanent wetlands. We cannot explain the apparent absence of this species from the Refuge, except to hypothesize that fluctuations in water level may strand the eggs or eliminate developmental habitat.

Spea bombifrons Plains Spadefoot Toad

This species ranges across the entire state of Nebraska, except for the southeastern comer. No records are available for Scotts Bluff County and only a single record (from near Bayard) is known for Morrill County (Lynch, 1985). This species requires ephemeral ponds that fill during heavy summer thunderstorms (just as does Bufo cognatus). We found no evidence of this species, probably because of the lack of ephemeral ponds adjacent to grassland habitats (used by adults).

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Lizards

Cnemidophorus sexlineatus viridis Prairie racerunner

The western known limit to the range of this species is along the North Platte River in western Morrill County (Lynch, 1985). When present, this is an obvious species, easily seen. Thus it is very unlikely that we would have missed this species. Optimal habitat already exists throughout the Refuge, in case this species ever colonizes the area.

Eumeces obsolerus Great Plains Skink.

This species has a wide range across the central Great Plains north to southern Nebraska. An isolated record exists for southeastern Morrill County dating from the 1930's (Lynch, 1985). We verified its occurrence in Morrill County with the collection of a single individual ca. 3 mi. north and 1.5mi. W of Broadwater [41° 38.483N, 102° 51$73W; 24May 2001] in southeastern Morrill County; however, we did not find it on the Refuge or in the rocky bluffs north of the Refuge. Nevertheless, it is possible that this very secretive species occurs near or on the Refuge.

Phrynosoma douglassi brevirostre Eastern Short-homed Lizard

In Nebraska this species occurs in rocky to gravelly habitats in the western Panhandle, both north and south of the North Platte. It has been recorded in extreme southwestern Sioux County, less than two miles from Stateline Island. Because of its preference for rocky soils, it is unlikely to be found on the Refuge, although it could occur on the rocky ridges and talus slopes north of the Lake Minatare and Lake Alice units.

Snakes

Heterodon nasicus nasicus Western Hognose Snake

The western hognose ranges across all of western Nebraska, particularly in areas of sandy soiL Previous records for Scotts Bluff County are known from Mitchell and from 7 mi. NE of Mitchell (Hudson, 1942; Lynch, 1985). Although we failed to observe this species on the Refuge, it probably occurs on every Unit.

General Conclusions

The herpetofauna of the North Platte National Wildlife Refuge is surprisingly depauperate in terms of diversity and numbers. Only 16 of 25 potential species in the area were verified on the Refuge, and no really large populations of any species (except perhaps the Bullsnake) were found. This pattern is likely due to three main factors:

1) The extensive manipulations of water levels in permanent bodies of water on the Refuge precludes the development of shoreline (emergent) vegetation in most areas. The result is the near absence of developmental habitat for aquatic turtles and amphibians.

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2) The e)ttensive canal system is a major impediment to dispersal into many of the units. For example, Lake Alice is effectively isolated by the Highline Canal from the much more diverse native grassland and rocky bluff habitats to the north.

3) The fragmented nature of the NPNWR no doubt contributes to the low diversity and low population sizes of the reptiles and amphibians there. Not only are home ranges of several species larger than many of the Units, but numerous roads between and through those Units contribute to frequent road kills. However, the units themselves, though small, cover a diverse assemblage of habitats (especially the abandoned prairie dog town east of Lake Minatare, a sliver of native prairie north of Lake Alice, the excellent ephemeral wetland southeast of Winter's Creek Lake, and the riparian shrub/woodland on Stateline Island.

Recommendations

If managing the North Platte Refuge for amphibians and reptiles were to become a priority, I believe that the following recommendations would do the most good for increasing the numbers and diversity of the herps. Basically, any management strategy that increases amphibian breeding and developmental habitat will directly benefit the amphibian fauna as well as indirectly benefit the reptiles (because of the increased prey base of amphibians).

1. Absolutely insure that the wetland southeast of Winters Creek Lake remains undisturbed.

2. Construct dams for temporary ponds ("tanks") in the central Sage unit near the bottom of the natural drainage channels. Perhaps one of these basins could be constructed with equipment already on the Refuge as an experiment. At the very least it would provide additional habitat for waterfowl and shorebirds, while serving as a test of this management recommendation.

3. Excavate depressions to near the water table at the Stateline unit to create ephemeral ponds (water levels would fluctuate with rainfall levels).

4. Deepen the soggy swale west of Winters Creek Lake (just south of the channel) so that it holds water longer than it currently does.

5. Excavate new depressions on the unit east of Winter's Creek Lake as well as deepen the center of the marsh already there. Care must be taken in each of these cases to insure that the ponds are still shallow enough to dry up nearly every year or to freeze solid each winter (to keep fish out).

6. Reduce raccoon and skunk populations (the primary predators on herps).

7. Expand the Lake Alice Unit northward, with the purchase of land to include rocky bluffs to the north. If such an expansion were possible, additional ephemeral pond basins could easily be constructed at the foot of the drainage ravines leaving the ridge.

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Future work

We plan followup field work during at least May 2002 (at our expense) in the hope of recording additional species.

REFERENCES

Baxter, G. T. and M.D. Stone. 1989. Amphibians and reptiles of Wyoming. Bulletin of the Wyoming Game and Fish Department 16:1-137.

Collins, J. T. 1982. Amphibians and reptiles in Kansas. University of Kansas Museum of Natural History, Public Education Series 8: 1-3.56.

Conant, R. and J. T. Collins. 1992. A Field Guide to the Reptiles and Amphibians: Eastern North America. Houghton-Mifflin, Boston. 450 pp.

Hudson, G. E. The amphibians and reptiles of Nebraska. Nebraska Conservation Bulletin 24:1-146.

Lynch, J. D. 1985. Annotated Checklist of the Amphibians and Reptiles of Nebraska. Transactions of the Nebraska Academy of Sciences 13:33-57.

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tigrinum

Locality records for Ambystoma tigrinum

woodhousii

Locality records for Bufo woodhousii

triseriata

. Locality records for Pseudacris triseriata

To henry

11

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Rona cotesbeiono

Locality records for Rana catesbeiana

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serpentina

Locality records for Chelydra serpentina

pi eta

Locality records for Chrysemys picta

ornata

Locality records for Terrapene ornata

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t

To.ttenry

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Trionyx

spiniferus

Locality records for Trionyx spiniferus

maculata

Locality records for Holbrookia maculata

Locality records for Sceloporns undulatus

To Henry

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. Eumeces multivirgatus

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Locality records for Eumeces multivirgatus

constrictor

Locality records for Coluber constrictor

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catenifer

Locality

radix

Locality records for Thamnophis radix

sirt a/is

Locality records for Thamnophis sirtalis

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Locality records for Crotalus viridis

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graciosus

Locality records for Sceloporus graciosus .

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triangulum

Locality records for Lampropeltis triangu-lum

Bufo

cognatus

Locality records for Bufo cognatus

Locality records for Spea bombifrons ·

Rona pipiens

sexlineatus

lineatus

Locality records for Rana pipiens

Locality records for Cnemidophorus sex-

Eumeces obso/etus

. Locality records for Eumeces obsoletus

Locality records for Phrynosoma douglassi