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Montana Animal Field Guide

Montana Field Guides

Western Spotted Skunk - Spilogale gracilis

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Potential Species of Concern

Global Rank: G5
State Rank: SU

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


 

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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).

General Distribution
Montana Range

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Western Hemisphere Range

 


Summary of Observations Submitted for Montana
Number of Observations: 21

(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
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 (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
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
  • Additional ReferencesLegend:   View WorldCat Record   View Online Publication
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    • 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, editors. 1982. Wild mammals of North America: biology, management, and economics. Johns Hopkins University Press, Baltimore, Maryland.
    • Dragoo, J. W., and R. L. Honeycutt. 1997. Systematics of mustelid-like carnivores. Journal of Mammalogy 78:426-443.
    • Flath, D. 1978. Written Communication of Western Spotted Skunk observation and specimen collection to Montana Natural Heritage Program, Helena, MT.
    • Flath, Dennis L., 1979, Nongame species of special interest or concern: Mammals, birds, reptiles, amphibians, fishes. January 1979.
    • Foresman, K. R. 2001. The wild mammals of Montana. American Society of Mammologists, Special Publication Number 12. Lawrence, KS. 278 p.
    • Hall, E. R. 1981. The mammals of North America, volumes I and II. John Wiley & Sons, New York, NY. 1181 p.
    • Hoffmann, R. S. and D. L. Pattie. 1968. A guide to Montana mammals: identification, habitat, distribution, and abundance. University of Montana, Missoula. 133 p.
    • Ingles, L. G. 1965. Mammals of the Pacific states. Stanford University Press, Stanford, California. 506 p.
    • Jellison, W. L. 1945. Spotted skunk and feral nutria in Montana. J. Mammal. 26. 432 pp.
    • Jellison, W.C. 1931. Little spotted skunk (Spilogale gracilis saxatilis), recorded for Montana. Journal of Mammalogy. V12. Page 314.
    • 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.
    • Leopold, A. S. 1959. Wildlife of Mexico. University of California Press, Berkeley.
    • Mead, R. A. 1968. Reproduction in western forms of the spotted skunk (genus SPILOGALE). J. Mamm. 49:373-390.
    • Pattie, D. L. and R.S. Hoffmann. 1992. Mammals of the North American Parks and Prairies. Self published.
    • 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). Bull. Am. Mus. Nat. Hist. 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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Citation for data on this website:
Western Spotted Skunk — Spilogale gracilis.  Montana Field Guide.  Montana Natural Heritage Program and Montana Fish, Wildlife and Parks.  Retrieved on October 1, 2014, from http://FieldGuide.mt.gov/speciesDetail.aspx?elcode=AMAJF05020
 
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