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Western Spotted Skunk - Spilogale gracilis
State Rank Reason (see State Rank above)
This species has rarely been observed and little data are available to assess the conservation status in Montana.
- Details on Status Ranking and Review
Western Spotted Skunk (Spilogale gracilis) Conservation Status Review
Review Date = 01/04/2012
Population Size
ScoreU - Unknown
CommentUnknown.
Range Extent
ScoreU - Unknown
CommentUnknown
Area of Occupancy
ScoreU - Unknown
CommentUnknown
Long-term Trend
ScoreE - Relatively Stable (±25% change)
CommentRiparian areas, rock outcrops and other habitats the species uses have probably been stable (+/-25%) since European arrival.
Short-term Trend
ScoreU - Unknown. Short-term trend in population, range, area occupied, and number and condition of occurrences unknown.
CommentNo data on trends available.
Threats
CommentThreats are largely unknown, but trapping, poisoning, and vehicle collisions may be the biggest threats to the species in Montana.
SeverityUnknown - Unknown
ScopeUnknown - Unknown
ImmediacyUnknown - Unknown
Intrinsic Vulnerability
ScoreC - Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance; or species has high dispersal capability such that extirpated populations soon become reestablished through natural recolonization (unaided by humans).
Environmental Specificity
ScoreC - Moderate. Generalist. Broad-scale or diverse (general) habitat(s) or other abiotic and/or biotic factors are used or required by the species but some key requirements are scarce in the generalized range of the species within the area of interest.
CommentSpecies uses a broad variety of habitats, but is often found near riparian areas and rock outcrops.
General Description
The Western Spotted Skunk is a small, relatively slender skunk with glossy black fur interrupted with distinct white stripes on the forward part of the body. The posterior part of the body has two interrupted white bands with one white spot on each side of the rump and two more at the base of the tail. The pattern of white lines and spots is individually unique. The top of the tail is black and the underside is extensively white. The tip of the tail is white. A white spot is present on the forehead and another in front of each ear. External measurements in males average 411 millimeters in total length, 122 millimeters for the tail and 50 millimeters for the hind foot. In females, external measurements average 387 millimeters in total length, 116 millimeters for the tail, and 47 millimeters for the hind foot. Males weigh about 630 grams, whereas females weigh about 450 grams (Foresman 2012).
Diagnostic Characteristics
The distinctive black and white pattern of spots and stripes and much smaller size of the Western Spotted Skunk distinguish them from the more common Stripped Skunk (Mephitis mephitis), which have two solid white stripes along the side of the body and are nearly twice as large.
The color pattern resembles that of the Eastern Spotted Skunk, but the white markings are more extensive. The black and white stripes on the upper back are nearly equal in width whereas in the Eastern Spotted Skunk the black areas are much more extensive than the white. The tip of the tail is white while the tail tips of Eastern Spotted Skunks are black. In addition to external characteristics, the breeding cycle of the spotted skunks are different (see Reproduction below).
Only Western Spotted Skunks and Striped Skunks are known to occur in Montana, however Eastern Spotted Skunks may also occur in the southeastern part of the state (Foresman 2012).
Species Range
Montana Range
Range Descriptions
Native
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations: 23
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Migration
Western Spotted Skunks are non-migratory.
Habitat
The habitat of the Western Spotted Skunk in Montana is not well known, but they have been found in arid, rocky and brushy canyons and hillsides. Information from other portions of its range suggest that when they are inactive or bearing young they occupy a den in rocks, burrows, hollow logs, brush piles, or under buildings.
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 (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- 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 2012, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
- 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 listed as associated with 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 listed as 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.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific 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 assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
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:
mtnhp.org/requests) 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. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- 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.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Grassland Systems
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Forest and Woodland Systems
Human Land Use
Shrubland, Steppe and Savanna Systems
Food Habits
Diets of Western Spotted Skunks in Montana have not been studied. Insects, rodents, small birds, and possibly bird eggs constitute most of their diet (Ingles 1965). Reptiles and amphibians are also taken (Leopold 1959), as are many types of fruits and berries.
Ecology
Ecological data is not available for this species in Montana. In general, den sites may be used by more than one individual, but adults are essentially solitary and nocturnal (Foresman 2012). Western Spotted Skunks may be locally common for a few years and then not seen for several more years (Pattie and Hoffmann 1992). Predators are not well known, but Great Horned Owls (Bubo virginianus) are probably the most important. Other sources of mortality include vehicles and deliberate killing by man, either by trapping or when they occur near human habitation. This species is probably best know for its habit of standing on its forelegs while arching its back and turning its hindquarters so that its anal glands are pointed at its antagonist when the animal feels threatened.
Reproductive Characteristics
No specific reproductive information for Montana is available, but information from other portions of its range suggests females come into estrus in September and most of them are bred by early October. Implantation of the embryo is delayed with the blastula stage of the embryo spending 180 to 200 days floating in the uterus of the female before becoming implanted. An average of four young are born in late April and May after a total gestation period of from 210 to 230 days. Young males may become sexually mature when only 3 or 4 months of age. Young leave the natal den about 1 month after birth and follow their mother until weaned at 7 weeks of age. Eastern Spotted Skunks do have delayed implantation. They mate between March and April and are reproductively isolated from the Western Spotted Skunk.
Management
Western Spotted Skunks are a Montana species of concern because of the limited number or records and limited distribution within the state. They are classified as a predator by Montana Fish, Wildlife and Parks for regulatory purposes. Harvest is not regulated and Montana Fish, Wildlife and Parks has recently requested information from trappers concerning take of this species to better define its range and status in Montana.
References
- Literature Cited AboveLegend:
View Online Publication
Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.- Ingles, L.G. 1965. Mammals of the Pacific states. Stanford University Press, Stanford, California. 506 pp.
- Leopold, A.S. 1959. Wildlife of Mexico. University of California Press, Berkeley.
- Pattie, D.L. and R.S. Hoffmann. 1992. Mammals of the North American Parks and Prairies. Self published.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Allen, A.W. 1987. The relationship between habitat and furbearers. Pages 164-179 in M. Novak, J.A. Baker, M.E. Obbard, and B. Malloch, eds. Wild Furbearer Management and Conservation in North America. Ontario Trappers Assn. and Ontario Ministry Nat. Res., Toronto, Ontario.
- Chapman, J.A., and G.A. Feldhamer. 1982. Wild mammals of North America: biology, management, and economics. Johns Hopkins University Press, Baltimore, Maryland.
- Deems, E.F., Jr. and D. Pursley (eds). 1978. North American furbearers: their management, research and harvest status in 1976. Int. Assoc. Fish and Wildlife Agencies and University of Maryland. 171 p.
- Dragoo, J. W., and R. L. Honeycutt. 1997. Systematics of mustelid-like carnivores. Journal of Mammalogy 78:426-443.
- Flath, D.L. 1979. Nongame species of special interest or concern: Mammals, birds, reptiles, amphibians, fishes. Wildlife Division, Montana Department of Fish and Game. Helena, MT.
- Foresman, K.R. 2001. The wild mammals of Montana. American Society of Mammalogists, Special Publication Number 12. Lawrence, KS. 278 pp.
- Hall, E.R. 1981. The mammals of North America, volumes I and II. John Wiley & Sons, New York, NY. 1181 pp.
- Hoffmann, R.S. and D.L. Pattie. 1968. A guide to Montana mammals: identification, habitat, distribution, and abundance. Missoula, MT: University of Montana. 133 p.
- Hoffmann, R.S., P.L. Wright, and F.E. Newby. 1969. The distribution of some mammals in Montana. I. Mammals other than bats. Journal of Mammalogy 50(3): 579-604.
- Jellison, W.C. 1931. Little spotted skunk (Spilogale gracilis saxatilis), recorded for Montana. Journal of Mammalogy. V12. Page 314.
- Jellison, W.L. 1945. General Notes: Spotted skunk and feral nutria in Montana. Journal of Mammalogy. 26(4): 432-443.
- Jones, J. K., Jr., R. S. Hoffman, D. W. Rice, C. Jones, R. J. Baker, and M. D. Engstrom. 1992. Revised checklist of North American mammals north of Mexico, 1991. Occasional Papers, The Museum, Texas Tech University, 146:1-23.
- Joslin, Gayle, and Heidi B. Youmans. 1999. Effects of recreation on Rocky Mountain wildlife: a review for Montana. [Montana]: Montana Chapter of the Wildlife Society.
- McDonough, M.M., A.W. Ferguson, R.C. Dowler, M.E. Gompper, and J.E. Maldonado. 2020. In Press Phylogenomic systematics of the spotted skunks (Carnivora, Mephitidae, Spilogale): Additional species diversity and Pleistocene climate change as a major driver of diversification. Molecular Phylogenetics and Evolution. 167:107266
- Mead, R.A. 1968. Reproduction in western forms of the spotted skunk (genus Spilogale). Journal of Mammalogy 49:373-390.
- Oechsli, L.M. 2000. Ex-urban development in the Rocky Mountain West: consequences for native vegetation, wildlife diversity, and land-use planning in Big Sky, Montana. M.Sc. Thesis. Montana State University, Bozeman. 73 p.
- Reid, F. 2006. Peterson Field Guide to Mammals of North America, 4th Edition. Houghton Mifflin Company: Boston and New York, 608 pp.
- Rust, H. J. 1946. Mammals of northern Idaho. J. Mammal. 27(4): 308-327.
- Thompson, L.S. 1982. Distribution of Montana amphibians, reptiles, and mammals. Bozeman: Montana Audubon Council. 24 pp.
- Van Gelder, R.G. 1959. A taxonomic revision of the spotted skunks (genus Spilogale). Bulletin of the American Museum of Natural History 117:229-392.
- Verts, B. J., L. N. Carraway, and A. Kinlaw. 2001. Spilogale gracilis. American Society of Mammalogists, Lawrence, KS. Mammalian Species No. 674:1-10.
- Verts, B.J. 1967. The biology of the striped skunk. Univ. Illinois Press, Urbana. vii+218 pp.
- Wilson, D. E., and D. M. Reeder (editors). 1993. Mammal Species of the World: a Taxonomic and Geographic Reference. Second Edition. Smithsonian Institution Press, Washington, DC. xviii + 1206 pp.
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