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Montana Field Guides

Western Skink - Plestiodon skiltonianus

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Species of Concern

Global Rank: G5
State Rank: S3

Agency Status
USFWS:
USFS:
BLM:
FWP Conservation Tier: 2

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General Description
The Western Skink has a shiny appearance because the body is covered in smooth and shiny, rounded scales. The dorsal coloration consists of brown, black, and golden-yellow or cream longitudinal stripes extending from the nose to the anterior portion of the tail. Younger individuals have brilliant blue tails that become progressively duller as they age. The belly is light gray to cream-colored, with a faint greenish-blue mottling. Males develop reddish-orange coloration on the chin and sides of the head during the breeding season. Adults are about 5.0 to 8.0 centimeters snout-vent length and up to 19 centimeters total length.

Diagnostic Characteristics
The Western Skink is the only lizard in Montana that appears to have a smooth and shiny body, and whose tail is blue in juveniles and young adults. Western Skinks lack a skin fold on the side of the body (present in Northern Alligator Lizards) and keeled scales (present in Greater Short-horned Lizards and Common Sagebrush Lizards). The distinct dorsal stripes of the Western Skink are not displayed by the other three species of Montana lizards. Only the Northern Alligator Lizard occurs in the range of the Western Skink in Montana.

General Distribution
Montana Range



Western Hemisphere Range

 


Summary of Observations Submitted for Montana
Number of Observations: 70

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

(Records associated with a range of dates are excluded from time charts)



Migration
No information is currently available for Montana. The species is non-migratory, but there are no data on home range sizes and movements.

Habitat
Little information is available. In Sanders County, Western Skinks were found in open ponderosa pine woodland in or near talus (Boundy 2001). Western Skinks were reported from Mineral, Missoula, and Ravalli counties in Agropyron spicatum-Poa sandbergii grasslands on southwest aspects (Ortega and Pearson 2001). These sites were described as gentle rolling terrain (less than 20% slope) with rocky areas imbedded, to rocky and steep terrain (average slope of 30%) with scattered ponderosa pine and Douglas-fir present. Many of the sites supported moderate to high densities of spotted knapweed (Centaurea maculosa).

Ecological Systems Associated with this Species
  • Details on Creation and Suggested Uses and Limitations
    How Associations Were Made
    We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
    1. Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point database associated with each ecological system;
    4. Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
    Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.  In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.  However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if point observations were associated with that system.  High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.  The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.  If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at bmaxell@mt.gov or (406) 444-3655.

    Suggested Uses and Limitations
    Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.  These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.  Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.  Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.  Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).  Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.

    Literature Cited
    • Adams, R.A.  2003.  Bats of the Rocky Mountain West; natural history, ecology, and conservation.  Boulder, CO: University Press of Colorado.  289 p.
    • Dobkin, D. S.  1992.  Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34.  Missoula, MT.
    • Foresman, K.R.  2001.  The wild mammals of Montana.  Special Publication No. 12.  Lawrence, KS: The American Society of Mammalogists.  278 p.
    • Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998.  Montana atlas of terrestrial vertebrates.  Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT.  1302 p.
    • Hutto, R.L. and J.S. Young.  1999.  Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32.  72 p.
    • Maxell, B.A.  2000.  Management of Montana’s amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species.  Report to U.S. Forest Service Region 1.  Missoula, MT: Wildlife Biology Program, University of Montana.  161 p.
    • Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath.  2004.  Amphibians and reptiles of Montana.  Missoula, MT: Mountain Press Publishing Company. 262 p.

Food Habits
Western Skinks feed primarily on insects and spiders, captives have eaten earthworms. Sometimes cannibalistic, with adults eating small juveniles (St. John 2002).

Ecology
This species of lizard is found up to 2150 meters elevation in the Pacific Northwest; record elevation in Montana is 1707 m (5600 ft) in Missoula County (Maxell et al. 2009). They are diurnal and may construct burrows up to 50 centimeters long (Nussbaum 1983).

Reproductive Characteristics
No information from Montana is currently available. Elsewhere Western Skink lays 2 to 10 eggs per clutch in a cavity under a rock or log; only a single clutch is produced per breeding season (St. John 2002, Maxell et al. 2009). Eggs are laid in June and July and hatch during late July to September; time from laying to hatching is about 30 days. Western Skink is the only native reptile in the Pacific Northwest that will stay with and guard their eggs until they hatch.

Management
No special management activities for Western Skinks are defined at this time. Incidental survey data indicate that Western Skinks may be locally abundant in some areas of low elevation conifer forest and grassland in Montana (Ortega and Pearson 2001), even though the range of this species in the state is restricted to the far western counties. Systematic surveys of appropriate habitats for this lizard are highly desirable to establish habitat associations and preferences, periods of activity, food habits, and relative abundances in Montana. Some populations may be vulnerable to habitat fragmentation from fire, logging, rural development.

References
  • Literature Cited AboveLegend:   View WorldCat Record   View Online Publication
    • Boundy, J. 2001. Herpetofaunal surveys in the Clark Fork Valley region, Montana. Herpetological Natural History 8: 15-26.
    • Maxell, B. A., P. Hendricks, M.T. Gates, and S. Lenard. 2009. Montana amphibian and reptile status assessment, literature review, and conservation plan, June 2009. Montana Natural Heritage Program. Helena, MT. 643 p.
    • Nussbaum, R. A., E. D. Brodie, Jr., and R. M. Storm. 1983. Amphibians and reptiles of the Pacific Northwest. University of Idaho Press. Moscow, ID. 332 p.
    • Ortega, Y.K. and D.E. Pearson. 2001. Occurences of the western skink (Eumeces skiltonianus) in grasslands of western Montana. Northwestern Naturalist 82(3):125-126.
    • St. John, A. D. 2002. Reptiles of the northwest: California to Alaska, Rockies to the coast. Lone Pine Publishing, Renton, WA. 272 p.
  • Additional ReferencesLegend:   View WorldCat Record   View Online Publication
    Do you know of a citation we're missing?
    • [NDTI] Northrop, Devine, and Tarbell Incorporated. 1994. Cabinet Gorge and Noxon Rapids hydroelectric developments 1993 wildlife study. Northrop, Devine, and Tarbell Incorporated, Portland, ME. 197 p.
    • Black, J.H. and R. Timken. 1976. Endangered and threatened amphibians and reptiles in Montana. p 36–37. In R.E. Ashton, Jr. (chair). Endangered and threatened amphibians and reptiles in the United States. Society for the Study of Amphibians and Reptiles Herpetological Circular 5: 1-65.
    • Brunson, R.B. 1955. Check list of the amphibians and reptiles of Montana. Proceedings of the Montana Academy of Sciences 15: 27-29.
    • Carlson, J. (Coordinator, Montana Animal Species of Concern Committee). 2003. Montana Animal Species of Concern. Helena, MT: Montana Natural Heritage Program and Montana Fish, Wildlife, and Parks. In Press. 12p.
    • Coues, E. and H. Yarrow. 1878. Notes on the herpetology of Dakota and Montana. Bulletin of the U.S. Geological Geographic Survey of the Territories 4: 259-291.
    • Crother, B.I. (ed.) 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico. SSAR Herpetological Circular No. 37:1-84.
    • Farley, C.T. and M. Emshwiller. 1996. Efficiency of uphill locomotion in nocturnal and diurnal lizards. Journal of Experimental Biology 199(3): 587-592.
    • Farley, C.T. and M.G. Emshwiller. 1993. Does maximum power output limit running speed? American Zoologist 33(5): 141A.
    • Fowlie, W.J. 1973. Occurrence of the western skink, Eumeces skiltonianus, along the Mojave River, Victorville, San Bernardino County, California. Herpeton 7(1):1-3.
    • Franz, R. 1971. Notes on the distribution and ecology of the herpetofauna of northwestern Montana. Bulletin of the Maryland Herpetological Society 7: 1-10.
    • Germaine, S.S. and H.L. Germaine. 2003. Lizard distributions and reproductive success in a ponderosa pine forest. Journal of Herpetology 37(4):645-652.
    • Goldberg, S.R. 2005. Reproductive cycle of the western skink, Eumeces skiltonianus (Sauria: Scincidae) in southern California. Texas Journal of Science 57(3):295-301.
    • Grismer, L.L. 1996. Geographic variation, taxonomy, and distribution of Eumeces skiltonianus and E. lagunensis (Squamata: Scincidae) in Baja California, Mexico. Amphibia-Reptilia 17(4): 361-375.
    • Hendricks, P. 1997. Lee Metcalf National Wildlife Refuge preliminary amphibian and reptile investigations: 1996. Montana Natural Heritage Program, Helena, MT. 21 p.
    • Hendricks, P. and J. D. Reichel. 1996. Amphibian and reptile survey of the Bitterroot National Forest: 1995. Montana Natural Heritage Program. Helena, MT. 95 p.
    • Maxell, B. A., J. K. Werner, P. Hendricks and D. L. Flath. 2003. Herpetology in Montana: a history, status summary, checklists, dichotomous keys, accounts for native, potentially native, and exotic species, and indexed bibliography. Society for Northwestern Vertebrate Biology, Northwest Fauna Number 5. Olympia, WA. 135 p.
    • Morrison, M.L., P.A. Aignerm, L.A. Nordstrom, and L.S. Hall. 1999. Habitat characteristics os sympatric Gilbert's and western skinks. Herpetological Review 30(1):18-20.
    • Peterson, C.R. and J.P. Shive. 2002. Herpetological survey of southcentral Idaho. Idaho Bureau of Land Management Technical Bulletin 02-3:1-97.
    • Punzo, F. 1982. Clutch and egg size in several species of lizards from the desert southwest. Journal of Herpetology 16(4):414-417.
    • Reichel, J. and D. Flath. 1995. Identification of Montana's amphibians and reptiles. Montana Outdoors 26(3):15-34.
    • Richmond, J.Q. and T.W. Reeder. 2002. Evidence for parallel ecological speciation in scincid lizards of the Eumeces skiltonianus species group (Squamata: Scincidae). Evolution 56(7): 1498-1513.
    • Rodgers, T. L. and W. L. Jellison. 1942. A collection of amphibians and reptiles from western Montana. Copeia (1):10-13.
    • Rodgers, T.L. and H.S. Fitch. 1947. Variation in the skinks (Reptilia: Lacertilia) of the skiltonianus group. University of California Publications in Zoology 48(4): 169-220.
    • Rutherford, P.L. and P.T. Gregory. 2003a. Habitat use and movement patterns of northern alligator lizards (Elgaria coerulea) and western skinks (Eumeces skiltonianus) in southeastern British Columbia. Journal of Herpetology 37: 98-106.
    • Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. 3rd Edition. Houghton Mifflin Company, Boston and New York. 533 p.
    • Storm, R. M., and W. P. Leonard (eds.). 1995. Reptiles of Washington and Oregon. Seattle Audubon Society. Seattle, WA. 176 pp.
    • Swaim, K.E. and S.M. McGinnis. 1992. Habitat associations of the Alameda whipsnake. Transactions of Western Section Wildland Society Vol. 28. p. 107-111.
    • Tanner, W.W. 1957. A taxonomic and ecological study of the western skink (Eumeces skiltonianus). Great Basin Naturalist 17(3-4): 59-94.
    • Tanner, W.W. 1988a. Eumeces skiltonianus (Baird and Girard). Western skink. Catalogue of American Amphibians and Reptiles No. 447: 1-4.
    • Taylor, E.H. 1935. A taxonomic study of the cosmopolitan scincoid lizards of the genus Eumeces with an account of the distribution and relationships of its species. The Kansas University Science Bulletin 23: 1-643.
    • Timken, R. No Date. Amphibians and reptiles of the Beaverhead National Forest. Western Montana College, Dillon, MT. 16 p.
    • Vitt, L.J., J.D. Congdon, and N.A. Dickson. 1977. Adaptive strategies and energetics of tail autotomy in lizards. Ecology 58(2): 326-337.
    • Werner, J. K., B. A. Maxell, P. Hendricks and D. L. Flath. 2004. Amphibians and Reptiles of Montana. Mountain Press Publishing Company: Missoula, MT, 262 pp.
    • Werner, J.K. and J.D. Reichel. 1994. Amphibian and reptile survey of the Kootenai National Forest: 1994. Montana Natural Heritage Program. Helena, MT. 104 p.
    • Werner, J.K. and J.D. Reichel. 1996. Amphibian and reptile monitoring/survey of the Kootenai National Forest: 1995. Montana Natural Heritage Program. Helena, MT. 115 pp.
    • Werner, J.K. and T. Plummer. 1995. Amphibian and reptile survey of the Flathead Indian Reservation 1993-1994. Salish Kootenai College, Pablo, MT. 55 pp.
    • Werner, J.K. and T. Plummer. 1995. Amphibian monitoring program on the Flathead Indian Reservation 1995. Salish Kootenai College, Pablo, MT. 46 p.
    • Werner, J.K., T. Plummer, and J. Weaslehead. 1998. Amphibians and reptiles of the Flathead Indian Reservation. Intermountain Journal of Sciences 4(1-2): 33-49.
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Citation for data on this website:
Western Skink — Plestiodon skiltonianus.  Montana Field Guide.  Montana Natural Heritage Program and Montana Fish, Wildlife and Parks.  Retrieved on April 20, 2014, from http://FieldGuide.mt.gov/detail_ARACH01110.aspx
 
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