Some Aspects of the Ecology of the Eastern Garter Snake (Thamnophis sirtalis sirtalis) in a Semi-Disturbed Habitat in West-Central Illinois

Abstract

Certain aspects of the ecology of a population of Thamnophis sirtalis sirtalis including population density, selection of cover objects, and sexual dimorphism and geographic variation in tail length proportions were studied on the campus of Western Illinois University in McDonough County, Illinois. The habitat of this area can be classified as semi-disturbed due to its heavy use by the university and students. Despite this degree of disturbance, a relatively successful population of garter snakes seems to exist based on population density estimates. Garter snakes showed a high association for cover objects, which may have been used for thermoregulation during warm and cool periods. Sexual dimorphism in tail length proportions (tail length/total length ratios) is present in this subspecies as reported previously in the literature. Geographic variation in tail length proportions exists for both males and females with three midwest and western races (T. s. parietalis, T. s. pickeringi, and T. s. concinnus) previously studied having longer tail length/total length mean ratios than T. s. sirtalis inhabiting west-central Illinois. One of these (T. s. concinnus) had a statistically highly significant difference in ratios from T. s. sirtalis for both males and females.