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Overview

Brief Summary

Description

"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."

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Mammal Species of the World
  • Original description: Merriam, C.H., 1890.  Results of a biological survey of the San Francisco Mountain region and desert of the Little Colorado in Arizona. North American Fauna,, 3:1-136.
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Distribution

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 )

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Range Description

The geographic range of the western spotted skunk extends from central Mexico through the western United States to British Columbia (Rosatte, 1987).
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occurs (regularly, as a native taxon) in multiple nations

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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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.

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Physical Description

Morphology

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

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Size

Length: 450 cm

Weight: 630 grams

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Size in North America

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
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Ecology

Habitat

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).

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Habitat and Ecology

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
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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.

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Migration

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.

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Trophic Strategy

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).

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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.

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General Ecology

Adults are essentially solitary.

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Life History and Behavior

Behavior

Perception Channels: tactile ; chemical

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Cyclicity

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

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Reproduction

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

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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.

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Conservation

Conservation Status

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

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Cuarón, A.D., Reid, F. & Helgen, K.

Reviewer/s
Duckworth, J.W. (Small Carnivore Red List Authority) & Schipper, J. (Global Mammal Assessment Team)

Contributor/s

Justification
This species is listed as Least Concern as they are widely distributed in a variety of habitats including human altered habitats. The species may be declining in parts of the United States but not at a rate fast enough to be threatened.
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National NatureServe Conservation Status

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

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Population

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
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Threats

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.
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Management

Conservation Actions

Conservation Actions
Spilogale g. amphialus is considered to be a subspecies of special concern by the state of California (Crooks, 1994).
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Relevance to Humans and Ecosystems

Benefits

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).

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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).

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Wikipedia

Western spotted skunk

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

Description[edit]

With a total length of 35–55 centimetres (14–22 in), the western spotted skunk is smaller than the striped skunk (Mephitis mephitis). The adult is boldly striped black and creamy white, mainly longitudinally, with a white spot on the head between the eyes, and a white patch below each ear. The ears are short and rounded. The animal has a conspicuously large, long haired black and white tail.

Distribution and habitat[edit]

Skeleton of Spilogale gracilis.

The western spotted skunk is found throughout the western United States, northern Mexico, and southwestern British Columbia.

Their habitat is mixed woodlands, open areas, and farmlands. They display deimatic (threat) behavior, raising their hind parts in the air and showing their conspicuous warning coloration to scare off predators. They spray by standing on their forelegs and raising their hindlegs and tail in the air.

Taxonomy and etymology[edit]

The western spotted skunk was first described by Clinton Hart Merriam in 1890;[3] its specific name, gracilis, is derived from the Latin for "slender".[4] 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.[5]

Subspecies[edit]

Seven subspecies are generally recognized:[1]

References[edit]

  1. ^ a b 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. 
  2. ^ Cuarón, A.D., Reid, F. & Helgen, K. (2008). Spilogale gracilis. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 27 January 2009.
  3. ^ ITIS Report. "ITIS Standard Report: Spilogale gracilis". Retrieved December 8, 2007. 
  4. ^ Verts, Carraway & Kinlaw. (2001) Mammalian Species: Spilogale gracilis. American Society of Mammalogists, 674: 1-10.
  5. ^ Smithsonian: National Museum of Natural History. "North American Mammals: Spilogale gracilis". Retrieved December 8, 2007. 
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Names and Taxonomy

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.

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