Mammal Species of the World
S. gracilis inhabits the western half of the United States. Some taxonomists call the western spotted skunk a subspecies of S. gracilis and others consider it a separate species.(Whitaker 1980)
Biogeographic Regions: nearctic (Native )
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: Range extends from southern British Columbia, Montana, and northern Wyoming southward through most of the western United States and into Mexico and Central America (south to Costa Rica). Range barely enters the Great Plains.
The western spotted skunk looks much like the eastern spotted skunk except that the white areas are more extensive. Both are relatively small and slender. They are black with a white spot on their forehead and in front of each ear. They have a pair of dorsolateral white stripes on the anterior portion of their bodies beginning at the back of their head, a pair of lateral stripes confluent with the spots in front of the skunk's ears, and a ventrolateral pair which begins just behind the forelegs. These cut off at mid-body and the posterior portion of the skunk's body has two interrupted white bands, a white spot on each side of the rump and two more at the base of the tail. The underside of the tail is white for nearly half its length and the tip is extensively white. The ears are short and low on the sides of the head. They have five toes on each foot but the claws on the front feet are more than twice as long as those on the back feet, sharp, and recurved. Males average 423mm in length (134 of that being tail) and 565 g in weight. Females average 360 mm (129 tail) and 368 g (Davis and Schmidley 1994).
Other Physical Features: endothermic ; bilateral symmetry
Length: 450 cm
Weight: 630 grams
Size in North America
Average: 425 mm males; 383 mm females
Range: 350-581 mm males; 320-470 mm females
Average: 700 g males; 400 g females
Range: 500-900 gm males; 200-600 gm females
Habitat and Ecology
The western spotted skunk prefers rocky bluffs and brush-bordered canyon stream beds. They make dens in rocky outcrops or hollow logs in the wild; however, they often live in close association with people, frequently nesting in rock fences or even attics (Davis and Schmidley 1994).
Comments: Brushy canyons, rocky outcrops (rimrock) on hillsides and walls of canyons. In semi-arid brushlands in U.S., in wet tropical forests in Mexico. When inactive or bearing young, occupies den in rocks, burrow, hollow log, brush pile, or under building.
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Skunks are omnivores. They enjoy eggs (wild or domestic, especially turkey eggs), young rabbits (Davis and Schmidley 1994), fruit and berries (Skunks), mice, voles, roots, and even arthropods such as grasshoppers (Savage 1999), and scorpions (Davis and Schmidley 1994).
Comments: Insects, rodents, small birds, and possibly bird eggs constitute most of diet (Ingles 1965). Reptiles and amphibian s also taken (Leopold 1959), as are many types of fruits and berries.
Adults are essentially solitary.
Life History and Behavior
Perception Channels: tactile ; chemical
Comments: More nocturnal than is striped skunk, rarely seen abroad during daylight hours. Active throughout the year.
The testes of adult and young males begin enlarging in March, producing sperm in May, and reach their peak by September. Females come into heat around in September and breeding begins. Most are bred by October when the formation of sperm is halted and the testes begin to regress again. The blastula stage of the embryo is free floating in the uterus for the first 180-200 days before implanting. Gestation usually lasts 210-230 days and litters ranging from 2-5 young are born in late April or May (Davis and Schmidley 1994). Baby skunks are called kits (Savage 1999). Young females become sexually mature at about 4 or 5 months of age and the cycle begins again (Davis and Schmidley 1994).
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual
Females breed during late September-October. Implantation is delayed, total gestation period lasts 210-230 days. Litter size is 4-6. Young leave nest about 1 month after birth, follow mother until almost full grown. Sexually mature in 4-5 months.
IUCN Red List Assessment
Red List Category
Red List Criteria
Recently described as a separate species from the eastern spotted skunk because of differences in color pattern, cranial features, reproductive physiology, and breeding season; the western spotted skunk is neither endangered nor threatened. It is adapting readily to the new sources of food and habitats provided by civilization (Davis and Schmidley 1994).
US Federal List: no special status
IUCN Red List of Threatened Species: least concern
National NatureServe Conservation Status
Rounded National Status Rank: N4 - Apparently Secure
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Relevance to Humans and Ecosystems
The skunk in general may be seen as a pest because of its affinity for making dens in human property combined with the foul smell it is capable of emitting. The fear that skunks carry rabies has shown to be no more worrisome than any other wild animal (Savage 1999). It is also known to nest in attics and steal turkey eggs from farmers (Davis and Schmidley 1994).
Skunks help keep down populations of animals such as rodents and grasshoppers which can be harmful to a farmer's crops (Savage 1999). They also eat scorpions, which may be useful to people by keeping down the population of this poisonous arthropod, especially since these skunk prefers to live near developed areas (Davis and Schmidley 1994). People have also begun descenting skunks and keeping them as pets because they are quite friendly and can be kitty litter trained (Skunks).
Western spotted skunk
The western spotted skunk (Spilogale gracilis) is a spotted skunk of the west of North America
With a total length of 35–45 cm (14–18 in), the western spotted skunk is smaller than the striped skunk (Mephitis mephitis). Males, which weigh 336 to 734 g (11.9 to 25.9 oz), are significantly heavier than females, at 227 to 482 g (8.0 to 17.0 oz), but only about 6% longer, on average. The adult is boldly striped black and creamy white, with three longitudinal stripes on each side of the front part of the body, and three vertical stripes on the hind-parts. One pair of longitudinal stripes runs either side of the spine, with the second pair running over the shoulders, and extending forward onto the face. The third pair is lower over the shoulders, and curves downward at the middle of the body to form the first pair of vertical stripes. Behind this, the second pair of vertical stripes rise from the knees to the rump, while the final stripes are often little more than spots.
The ears are short and rounded, while the face is marked with a white spot between the eyes, and a white patch below each ear. The animal has a conspicuously large, long-haired tail, measuring 10 to 16 cm (3.9 to 6.3 in). The hair on the tail is mostly black, but is white at the tip, and sometimes also on the upper surface. The claws on the fore-feet are longer, and more curved, than those on the hind feet.
As with other related species, western spotted skunks possess a pair of large musk glands that open just inside the anus, and which can spray their contents through muscular action. The musk is similar to that of striped skunks, but contains 2-phenylethanethiol as an additional component, and lacks some of the compounds produced by the other species. These differences are said to give western spotted skunk musk a more pungent odor, but not to spread as widely as that of striped skunks.
Distribution and habitat
Behavior and biology
Western spotted skunks are nocturnal omnivores, feeding on insects, small vertebrates, such as mice and lizards, and berries. Common insects eaten include beetles and caterpillars. Golden eagles are among their few predators. They spend the day in dens, and are usually solitary, although sometimes two or three females will share a single burrow.
When threatened, western spotted skunks display threat behavior, stamping their fore-feet before raising their hind parts in the air and showing their conspicuous warning coloration. While they can spray by standing on their forelegs and raising their hindlegs and tail in the air, they more commonlly do so with all four feet on the ground, bending their body around so that both their head and their tail face the attacker.
Western spotted skunks typically breed in September, although both sexes remain fertile for several months thereafter if they fail to breed early. After fertilisation, the embryo develops to the blastocyst stage, but then becomes dormant for several months before implanting in the uterine wall around April. Including this period of delayed implantation, gestation lasts 230 to 250 days, with the litter of two to five young being born in May. At birth, the young are blind and almost hairless, weighing around 11 g (0.39 oz). Western spotted skunks have lived for almost ten years in captivity.
Taxonomy and etymology
The western spotted skunk was first described by Clinton Hart Merriam in 1890; its specific name, gracilis, is derived from the Latin for "slender". Although it was thought for years to be conspecific with the eastern spotted skunk (S. putorius), the presence of delayed implantation in the western spotted skunk clearly sets it apart.
Seven subspecies are generally recognized:
- S. g. amphialus Dickey, 1929 - Channel Islands spotted skunk (Channel Islands of California)
- S. g. gracilis Merriam, 1890 - from south-eastern Washington to the extreme west of Oklahoma
- S. g. latifrons Merriam, 1890 - southwestern British Columbia to western Oregon
- S. g. leucoparia Merriam, 1890 - southern Arizona, New Mexico, and Texas, and northern Mexico
- S. g. lucasana Merriam, 1890 - southern Baja California
- S. g. martirensis Elliot, 1903 - northern and central Baja California
- S. g. phenax Merriam, 1890 - California
- Wozencraft, W. C. (2005). "Order Carnivora". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 623. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Cuarón, A.D., Reid, F. & Helgen, K. (2008). Spilogale gracilis. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 27 January 2009.
- Verts, B.J., Carraway, L.N. & Kinlaw, A. (2001). "Spilogale gracilis". Mammalian Species: Number 674: pp. 1–10. doi:10.1644/1545-1410(2001)674<0001:SG>2.0.CO;2.
- Baker, R.H. & Baker, M.W. (1975). "Montane habitat used by the spotted skunk (Spilogale putorius) in Mexico". Journal of Mammalogy 56 (3): 671–673. doi:10.2307/1379480.
- von Bloeker, J.C. (1937). "Mammal remains from detritus of raptorial birds in California". Journal of Mammalogy 18 (3): 360–361. doi:10.2307/1374214.
- Crooks, K.R. & Van Vuren, D. (1995). "Resource utilization by two insular endemic mammalian carnivores, the island fox and island spotted skunk". Oecologia 104 (3): 301–307. doi:10.1007/BF00328365.
- Mead, R.A. (1968). "Reproduction in western forms of the spotted skunk (genus Spilogale)". Journal of Mammalogy 49 (3): 373–390. doi:10.2307/1378196.
- Foreman, K.R. & Mead, R.A. (1973). "Duration of post-implantation in a western subspecies of the spotted skunk (Spilogale putorius)". Journal of Mammalogy 54 (2): 521–523. doi:10.2307/1379146.
- Constantine, D.G. (1968). "Gestation period in the spotted skunk". Journal of Mammalogy 42 (3): 421–422. doi:10.2307/1377064.
- Egoscue, H.J., Bittmein, J.G. & Petrovich, J.A. (1970). "Some fecundity and longevity records for captive small mammals". Journal of Mammalogy 51 (3): 622–623. doi:10.2307/1378407.
- ITIS Report. "ITIS Standard Report: Spilogale gracilis". Retrieved December 8, 2007.
- Smithsonian: National Museum of Natural History. "North American Mammals: Spilogale gracilis". Retrieved December 8, 2007.
Names and Taxonomy
Comments: This species has been included in S. putorius by some authors (e.g., Wozencraft, in Wilson and Reeder 1993). Mead (1968) argued that gracilis and possibly leucoparia, both of which were included in S. putorius by Van Gelder (1959) and Hall (1981), are reproductively isolated from eastern populations and therefore should be considered distinct species. Jones et al. (1992), Baker et al. (2003), and Wozencraft (in Wilson and Reeder 2005) recognized S. gracilis and S. putorius as separate species.
Based on patterns of mtDNA variation in Mustelidae, Dragoo and Honeycut (1997) recommended that skunks (Mephitis, Conepatus, Spilogale) and the stink badgers (Mydaus) be separated as a distinct family (Mephitidae). Wozencraft (in Wilson and Reder 2005) recognized Mephitidae.