UBC Theses and Dissertations
Spatial ecology and life history of the great basin gophersnake (pituophis catenifer destericola) in British Columbia's Okanagan valley White, Kathleen Edith
The range of a species often extends across a diverse landscape, necessitating that individuals make different movement and habitat decisions, despite consistent food and shelter requirements. Great Basin gophersnakes (Pituophis catenifer deserticola) are threatened in Canada, where they occur at the northern extent of their range in southern interior river valleys of British Columbia such as the Okanagan Valley. I followed 39 radio-transmittered adult gophersnakes at four sites in the Okanagan, to obtain information on life history, movement and range patterns, and habitat use. Habitat selection and movement patterns exhibited by gophersnakes differed between study sites, sexes, and months, indicating that snake choice varies depending on resources and life history traits. Despite these fine-grain differences, males moved more than females in the spring. In addition to this, females moved more than males in the summer and fall. Differences in movement and range were apparent among the study sites. Habitat selection differed by study site, however rock-outcrops were consistently selected overall. Microhabitat selection varied, but retreat sites including logs, rocks, and holes in the ground, were consistently located closer than random. Hibernation sites in the south Okanagan were in rock features, while in the north Okanagan a good proportion were in rodent burrows in hillsides. Hibernation site fidelity was low, and annual reproduction was common. Oviposition sites were on south-facing slopes of moderate grade with little to moderate grass cover. Three ecdysis periods were observed when most or all transmitter-equipped snakes shed their skin. These findings will be very valuable to species conservation goals in British Columbia when developing guidelines on the habitats and sizes of areas to protect. With an iii understanding of the movement and ranges patterns exhibited by individuals, the area required to sustain a healthy population of gophersnakes can be determined. Knowledge of the habitats and microhabitats gophersnakes select makes it possible to identify and protect important areas at sites known to contain gophersnakes, including the Vaseux, Ripley, and Vernon study sites. Characterization of hibernation and oviposition sites allows surveys to identify these areas in locations that may support gophersnakes. Finally, identification of the timing of various important life history behaviours means human disturbance can be avoided during mating and oviposition periods, especially on sites such as Vernon, where land is used for multiple purposes.
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