Orientation Abilities and Mechanisms in Nonmigratory Populations of Garter Snakes (Thamnophis sirtalis and T. ordinoides)

I tested the navigational abilities in nonmigratory populations of garter snakes (Thamnophis sirtalis and T. ordinoides) from Spectacle Lake Provincial Park on Vancouver Island, British Columbia, Canada. Displacement studies were carried out from 1986-88 to determine the level of orientational abilities present in each species and to examine potential orientation cues. Snakes were displaced from their home range and tested in an arena under a variety of conditions. The results demonstrated that nonmigratory T. sirtalis possessed advanced navigational abilities. Advanced abilities may be absent in T. ordinoides. Thamnophis sirtalis demonstrated time-compensated solar orientation as determined by 6-h phase-delayed tests. Pheromone trails produced by gravid females, but not by males, may also provide an orientation guide for T. sirtalis under some conditions. Thamnophis ordinoides did not respond in a discernible way to either solar or pheromonal cues. The findings of this study were compared with similar tests performed on a migratory population of T. sirtalis. Navigational skills vary little between migrating and nonmigrating populations of the same species but may be poorly developed in nonmigratory species.