Western skink (Eumeces skiltonianus) COSEWIC assessment and status report: chapter 3

Species Information

Species Description

The Western Skink, Eumeces skiltonianus (Baird and Girard), is a medium-sized lizard (up to 83 mm in snout-vent length) with smooth, shiny scales, a pointed head, and short legs characteristic of skinks (Gregory and Campbell 1984, Tanner 1988). Four longitudinal, light-coloured stripes extend from the head to the base of the tail. The stripes contrast with the dark-coloured, brown dorsum and grey or black sides (Stebbins 1954, Storm and Leonard 1995). The tail is blue, often vividly coloured in juveniles. Apart from fading in brightness, the colouration of adults is similar to that of young (Tanner 1957, Stebbins 1985). Reddish patches may be present on the chin and sides of the head of breeding adults of both sexes but is brighter in males (Stebbins 1954, Gregory and Campbell 1984).

Taxonomy

The family Scincidae is a large group of lizards (about 85 genera and over 1000 species) with a worldwide distribution (Cook 1984). Three species occur in Canada: Eumeces fasciatus, E. septentrionalis, and E. skiltonianus. Eumeces skiltonianus is closely related to E. gilberti in southwestern United States (Rodgers and Fitch 1947, Tanner 1957). Four subspecies of E. skiltonianus are recognized: skiltonianus, utahensis, interparietalis, and lagunensis (Tanner 1988).  The range of E. s. skiltonianus extends northward into south-central British Columbia.  [Editor’s note: The Society for the Study of Amphibians and Reptiles (SSAR) Committee on Standard English and Scientific Names identifies “Skilton’s skink” as a common name for E. s. skiltonianus (Crother 2000).]

Research

The natural history of E. skiltonianus is poorly known, particularly for populations at the northern portion of the species' geographical distribution. The most comprehensive ecological studies are those of Tanner (1943, 1957) in Utah. Rogers and Memmler (1943) and Punzo (1982) reported on reproduction of the species in California. Vitt and Pianka (1994), and Farley and coworkers (Farley and Emshwiller 1996, Farley 1997, Farley and Ko 1997) examined the efficiency and mechanics of locomotion. Brattstrom (1965), and Cunningham (1966) reported on thermal preferences. Rogers and Fitch (1947), and Tanner (1957) examined systematics of western Eumeces. Tanner (1988) provided a summary of distribution and available literature on the species. Other summary accounts are in Van Denburgh (1922), Smith (1946), Stebbins (1954, 1972, 1966, 1985), Nussbaum et al. (1983), and Storm and Leonard (1995); summaries with emphasis on British Columbia are in Carl (1944), Cook (1984), and Gregory and Campbell (1984).

In addition to published literature, information available for this report consisted of distribution records based on museum specimens and inventory reports.  Recent distribution records from the Okanagan were available from data bases compiled as part of various inventory projects and from personal files of Mike Sarrell. Distribution records and some preliminary data from an ongoing study on reproductive biology of lizards in the Creston Wildlife Management area were also available (Ph.D. dissertation work by Pam Rutherford, Department of Biology, University of Victoria).

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