Western skink (Eumeces skiltonianus) COSEWIC assessment and status report: chapter 7

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Population Sizes and Trends

Population Density

Nothing is known of population densities of E. skiltonianus in British Columbia. At all but one site sampled in the Creston Valley Wildlife Management Area from 1996-1998, the skinks were caught much less frequently than were alligator lizards (Elgaria coerulea) and appeared to be less abundant (Pam Rutherford, pers. comm.). At one rocky site, however, the skinks were more numerous than alligator lizards. No estimates of population densities are available from the United States.

Population Distribution and Persistence

Tanner (1957) noted that the skinks are locally abundant in California and Utah. He attributed the local distribution pattern primarily to habitat suitability but also noted that, "field data suggest a definite tendency towards gregariousness in this species" (p. 89). The skinks appear to be similarly unequally distributed within their range in British Columbia. Distribution records are concentrated in the major valleys and their vicinities, including the Kootenay Lake, Lower Arrow Lake, Shuswap Lake, Okanagan, Slocan, and Similkameen River valleys (Fig. 2). Orchard (1980) noted that the species is locally abundant with concentrations centered in some areas, such as around Nelson and in the southern Okanagan. The skinks also appear to be locally distributed at smaller scales. For example, Pam Rutherford (pers. comm.) caught skinks only at a few of her study sites in the Creston Wildlife Management Area.

Recent distribution records (since 1990) exist only from the Creston and Grand Forks areas and from southern Okanagan. Notably, there are no recent records from the vicinity of Penticton in the west and from West Kootenays apart from the Creston area. The most recent record from near Salmon Arm is from 1987. The lack of recent records from the above areas may well reflect a lack of search effort rather than the disappearance of the species.

Population Trends

Population trends of E. skiltonianus in British Columbia are unknown. In the United States, populations have been reported to fluctuate widely from year to year (Fitch 1936, Smith 1946, Tanner 1957). Tanner (1957) attributed such fluctuations to vegetation succession that altered habitat suitability and to adverse weather conditions, such as droughts, that affected reproductive success in a given year.