The ecology of Western Painted Turtles (Chrysemys Picta Belli) in a Northern Canadian Reservoir

Impoundment of water by hydroelectric reservoirs and resulting fluctuations in water levels (drawdown zone) may have significant impacts on the surrounding ecosystems. For herpetofauna that live in cold climates, such human-induced alterations may amplify the difficulties in coping with the environment. My study explored the ecology of an extreme northern population (Revelstoke, British Columbia, Canada) of western painted turtles (WPT; Chrysemys picta bellii) inhabiting a reservoir that constantly fluctuates due to hydroelectric operations. The potential challenges this environment poses include inundation of nesting sites, increased winter mortality due to water level changes, and changes in the availability of aquatic habitat. I used radio telemetry and mark-recapture to identify where turtles were nesting and overwintering, and to assess demographics and turtle behaviour in relation to the changing water levels. My data suggest that adults and juveniles of both sexes used and overwintered in the drawdown zone. Nest inundation as a result of reservoir operations did not appear to be a significant threat to the animals as all detected nests lay above the high-water mark. Similarly, no incidents of turtle mortality were directly attributable to reservoir operations. Changes in water levels did affect habitat availability: areas in which turtles were located during early spring were subsequently lost as water levels rose, while flooding in other areas created seasonal, suitable habitat for turtles that otherwise was not accessible. Modelling turtle response to water levels, water temperature, and season suggested that changes in water levels did not significantly impact behaviour as measured. Appropriate management for this species and other semi-aquatic species that reside within drawdown zones is complex, given the reliance on both terrestrial and aquatic habitat, the life cycles of the species, movement, changing water levels, and subzero winter temperatures. This research provides a baseline for understanding the ecology of turtles in dynamic northern environments.