E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Plestiodon skiltonianus (Baird and Girard, 1852)
Western Skink
Family: Scincidae
Species account author: Pamela Rutherford.

© Pamela Rutherford  Email the photographer   (Photo ID #14670)

E-Fauna BC Static Map
Distribution of Plestiodon skiltonianus in British Columbia
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Species Information

The Western Skink is a small lizard, with a typical cigar-shaped body and short legs that is possessed by most skinks. They can grow to almost 10 cm in body length and have tails that are up to 12 cm long (Rutherford, unpublished). They are brown in colour, with two pale stripes that run the length of the body on either side (Cook 1984). Breeding males develop bright orange chins during the breeding season in the spring; the colour fades through the summer (Gregory and Campbell 1984). The young have brighter stripes and a vivid, blue tail; the colours of both fade as the animals age.

Biology

Reproduction

Western Skinks are egg layers, laying one clutch per year of 2-6 eggs (COSEWIC 2002). In British Columbia, Mating takes place in May and June, egg laying in June and July, and hatching in August and early-September. Nests are typically located under rocks, and the chambers can extend several centimetres underground (Tanner 1957). Females remain with eggs until hatchling, likely to protect them from predators and to move them around the nest to optimize heat and moisture conditions for egg development (COSEWIC 2002, Rutherford, pers. obs.).
Diet

Western Skinks consume a variety of types of insects and their eggs (e.g. caterpillars, moths, beetles, grasshoppers, spiders, isopods, and crickets), although ants have never been found in their stomach contents (Tanner 1957). It is likely that invertebrates are consumed in available proportions, but food consumption in nature has not been studied. Newborn skinks likely eat smaller insects, although little is documented about their food habits, even in captivity (COSEWIC 2002).
Behaviour

Western Skinks spend much of their time in retreat sites and are uncommon in the open (Rutherford and Gregory 2003). Adult males are most easily located in early spring during the breeding season, and gravid females are easily located in late summer on a cooler day.
Seasonal Charactertistics

In British Columbia, Western Skinks emerge from hibernation in mid-April. Mating takes place shortly after emergence from hibernation from mid-April to late-May. Egg laying occurs in June and July, and young are born from mid-August to early-September. Animals enter hibernation in late-September (Rutherford 2002). The active period is extended in United States populations. At Creston, British Columbia, hibernation occurs in the summer habitat with no seasonal migration, although movement away from hibernation sites has been reported for some United States populations. They are site-faithful; individuals are typically recaptured within ten metres of a previous capture, both within a summer season and from year to Western Skink (Plestiodon skiltonianus)(Rutherford and Gregory 2003). Movements of greater than one hundred metres are rare.

Habitat


Western Skinks can be found in a wide range of habitats: dry woodland, grassland, along the banks of creeks, and in forest clearings (COSEWIC 2002). The presence of abundant cover is important for hiding and includes rocks, logs or herbaceous cover, although they appear to avoid heavy brush (Tanner 1957). Basking typically occurs in protected areas such as crevices or under rock cover (Rutherford and Gregory 2003). They are often found on forest edges or in forests but their association with forests is not clear. Hibernation requires access to rock crevices below the frostline.

Distribution


In Canada, Western Skinks occur in south-central British Columbia. They are found as far east as Kootenay Lake and as far west as Princeton, although there has been one recorded sighting in Courtney on Vancouver Island (McNicholl 1975). The North American range extends from British Columbia to the southern tip of Baja California, and from the Pacific coast in Oregon to western Montana, Idaho and Utah (Tanner 1988).

Conservation


The greatest immediate threats to Western Skinks are habitat loss and alteration. Their small geographic range, site-fidelity and dependency on rock and vegetative cover makes them vulnerable to modification of their localized habitat (COSEWIC 2002). Grasslands in southcentral British Columbia are perhaps the most threatened ecosystems in the province. Removal of rock for road construction and quarrying is another significant threat. They are disturbed by people moving near basking sites and this disturbance may be detrimental to nesting females. There is likely little road mortality, although roads may act as barriers. They are attractive to collectors, although their secretive behaviour may make it difficult for people to capture them (COSEWIC 2002).

Taxonomy


Plestiodon (formerly Eumeces) skiltonianus (Baird and Girard, 1852)—Western Skink): This species formerly belonged to the genus Eumeces; all North American members of this genus are now included in the genus Plestiodon (Smith 2005). Eumeces is reserved for North African species.

Subspecies taxonomy (Tanner 1988)

P. s. interparietalis (Tanner 1957)—Coronado Skink (North and Western Baja California, Southern San Diego County in California)

P. s. skiltonianus (Baird and Girard 1852)—Skilton’s Skink (Southcentral British Columbia, Washington, Western Montana, Northern Idaho, Oregon (except Northwestern corner), Northwestern Nevada, Northeastern and Western California to San Diego County)

P. s. utahensis (Tanner 1957)—Great Basin Skink (Southern Idaho, Nevada (except western edge), Utah, Northern Arizona)

Comments


Known predators of the Western Skink include: racers, rattlesnakes, garter snakes, rubber boas, shrikes, red-tailed hawks, and cats (COSEWIC 2002). Western Skinks use their tail as a decoy and are likely to drop (autotomize) their tail if captured. At Creston, British Columbia, almost 50% of skinks captured had autotomized their tail, at some point in the past (Rutherford, unpublished).

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS3S4BlueSC (Nov 2014)
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Synonyms and Alternate Names

Eumeces skiltonianus (Baird and Girard, 1852)

Additional Range and Status Information Links

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 18/11/2019 5:16:54 AM]
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