Regulation of Seasonal Mating Behavior in Thamnophis sirtalis parietalis

At latitudes of about 50?-55? N in Manitoba, Canada, the red-sided garter snake (Thamnophis sirtalis parietalis) hibernates in concentrated aggregations of several thousand individuals and mates shortly following emergence in late April or early May. Mating is most intense when air temperatures are above 15 C, and lasts about 4 weeks. Mating activity of about 10 days duration can be induced in the laboratory by: 1) collecting snakes at the hibernaculum site in September, subjecting them to 5 C, OL24D for at least 4 months and then transferring them to 25 C, 12L12D; and 2) collecting snakes at the hibernaculum site in late April or early May, holding them at 5 C, OL24D, and transferring them to 25 C, 12L12D at any time until August. Food intake is completely inhibited for 3 days following the transfer, and then increases progressively in an inverse relationship to declining mating activity. A transfer from 5 C, OL24D to 5 C, 12L12D does not result in mating. On the basis of these experiments we hypothesize that the increase in body temperature experienced by the red-sided garter snake during emergence from hibernation induces the intense mating activity observed shortly following emergence.