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Western Spotted Skunk

Spilogale gracilis

Summary 2

The western spotted skunk (Spilogale gracilis) is a spotted skunk of the west of North America.

Behaviour 3

Perception Channels: tactile ; chemical

Conservation actions 4

Conservation Actions

Spilogale g. amphialus is considered to be a subspecies of special concern by the state of California (Crooks, 1994).

Conservation status 5

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

Cyclicity 6

Comments: More nocturnal than is striped skunk, rarely seen abroad during daylight hours. Active throughout the year.

Description 7

"Eastern and Western Spotted Skunks were for years thought to be one and the same species, but they differ in an important detail of the reproductive process. In the Western Spotted Skunk, a very long period of delayed implantation occurs. The fertilized eggs begin to develop, then stop growing at a very early stage and float freely in the uterus. When they ""implant,"" attaching to the uterine wall, growth begins again. Breeding occurs in September or October and the fertilized eggs remain on hold for 6-7 months. In March or April, development resumes, and two to six kits are born about a month later, coinciding with a plentiful food supply. The skunks are carnivorous, feeding on mice and other small mammals, insects, lizards, birds, and carrion. They also eat some vegetable matter."

Links:
Mammal Species of the World

Distribution 8

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 )

Distribution 9

occurs (regularly, as a native taxon) in multiple nations

Ecology 10

Adults are essentially solitary.

Habitat 11

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).

Habitat 12

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.

Habitat and ecology 13

Habitat and Ecology

The spotted skunk has been recorded in a big spectrum of habitats varying from open lowlands to mountainous areas (Baker and Baker, 1975), streams to rocky places, beaches to human buildings and other disturbed areas, chaparral among others (Rosatte, 1987; Verts et al., 2001). The species has been found at elevations of 2,500 m in California (Orr, 1943). Doty and Dowler (2006) reported that M. mephitis and S. gracilis coexist in habitats of west-central Texas that provide sufficient cover for S. gracilis. Its an omnivorous species, feeding primarily on insects and small mammals (Ewer, 1973; Kurten and Anderson, 1980) and carrion, berries, fruits and other (Bailey, 1936; Clark and Stromberg, 1987; Maser et al. 1981).

Systems
  • Terrestrial

Migration 14

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.

Morphology 15

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

Population 16

Population

Populations of western spotted skunks have been known to fluctuate in numbers and the animal is generally not common on the United States plains (Polder, 1968; Choate et al., 1974). Few studies have been published on the home range, population density, and mortality of spotted skunks (Howard and Marsh, 1982). Crabb (1948) found that the western spotted skunk in Iowa maintained a home range of 64.8 ha at densities of 2.2 individuals/km2.

Population Trend
Decreasing

Range description 17

The geographic range of the western spotted skunk extends from central Mexico through the western United States to British Columbia (Rosatte, 1987).

Reproduction 18

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

Size in north america 19

Sexual Dimorphism: Males are 7%-10% larger than females.

Length:
Average: 425 mm males; 383 mm females
Range: 350-581 mm males; 320-470 mm females

Weight:
Average: 700 g males; 400 g females
Range: 500-900 gm males; 200-600 gm females

Taxonomy 20

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.

Threats 21

Major Threats

Humans have been the main cause of mortality for spotted skunks, especially as a result of automobile roadkills. Spotted skunks are also trapped, shot, and poisoned during predator control tactics (Rosatte, 1987). The pelts of both eastern and western spotted skunks represent an insignificant fraction of the modern fur trade. Pesticides present a significant threat over portions of the range.

Trophic strategy 22

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).

Trophic strategy 23

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.

Uses 24

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).

Uses 25

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).

Sources and Credits

  1. (c) Kim Cabrera, some rights reserved (CC BY-NC-ND), uploaded by Kim Cabrera
  2. Adapted by Kim Cabrera from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Spilogale_gracilis
  3. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31424020
  4. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31269424
  5. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31424024
  6. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28935203
  7. (c) Smithsonian Institution, some rights reserved (CC BY), http://eol.org/data_objects/16146988
  8. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31424016
  9. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28935197
  10. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28935199
  11. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31424017
  12. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28935201
  13. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31269422
  14. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28935200
  15. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31424018
  16. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31269421
  17. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31269420
  18. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31424019
  19. (c) Smithsonian Institution, some rights reserved (CC BY), http://eol.org/data_objects/6625673
  20. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28935190
  21. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31269423
  22. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31424021
  23. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28935202
  24. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31424023
  25. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31424022

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