Control of Male Sexual Behaviour in the Canadian Red-Sided Garter Snake

Abstract

The red-sided garter snake, Thamnophis sirtalis parietalis, ranges farther north than any other reptile in the Western Hemisphere. Collapsed caverns and breaks in the limestone strata over much of Western Canada provide suitable overwintering sites, called hibernacula or dens, where the snakes take refuge from the harsh Canadian winter. In Manitoba the seasonal changes in temperature are extreme. Winter temperatures are frequently −40°C or lower and snow cover may be continuous from late September through May. In the brief spring and summer, temperatures may climb as high as 40°C. No food or surface water is available at most den sites and fall and spring migrations over long distances to and from suitable summer feeding grounds are required. Mating and feeding are mutually exclusive activities in the red-sided garter snake. This exclusivity places a further constraint on the animals in the brief summer. Because the season for both growth and reproduction may be as brief as 3 months, and because reproduction is physically demanding on the adults, the timing or reproduction is critical.