Snakes in the Subarctic: Fall Phenology of the Red-Sided Garter Snake (Thamnophis sirtalis parietali

Balchan, Neil R.

Department of Biological Sciences

University of Manitoba

Winnipeg, MB R3T 2N2, Canada

Seasonal movements and accompanying behavioural changes are critical to a species’ ability to persist in a variable environment. Long distance migrations are frequently associated with birds, mammals, and fish, but they occur in additional taxa under necessitating circumstances. In Interlake Manitoba, the Red-sided Garter Snake (Thamnophis sirtalis parietalis) makes long-distance movements between summer foraging habitats and communal hibernacula, where winter congregations can number into the thousands. Suitable hibernacula serve as limiting factors in the far north, further strengthening the need to travel great distances to reach them. While the spring movements undertaken by snakes in this region are well studied, fall movements have remained largely unexplored. Basic aspects of fall movement ecology such as migration timing, time spent at the hibernaculum, and changes in body condition remain unstudied. I will explore fall movement ecology in a population of Interlake Manitoba garter snakes to characterize phenology over this period. I will track fall migration of the population to determine the time span of movements and distribution of individuals within this time span. I will study fall ecology at the hibernaculum, particularly snake numbers through time, sex and size biases through time, inter-den movement, and changes in body condition. Lastly, I will determine ingression timing into the hibernaculum and relate this information to corresponding environmental parameters. As fall events set the stage for hibernation success and spring reproduction, this period is a critical component of the snake’s annual cycle. Garter snakes represent a significant transfer of energy from aquatic to terrestrial systems, and are an important prey species in this region. Conservation of northern snake populations must consider species ecology throughout the year for effective management.