Spatial ecology and habitat selection of two sympatric snake species in southwestern Saskatchewan

My research focused on the spatial ecology and habitat use of two sympatric snake species in a grassland community. The eastern yellow-bellied racer ( Coluber constrictor flaviventris) is a Threatened species in Canada, primarily because its range is restricted to a small area of the southern prairies. There have been no previous studies published on the eastern yellow-bellied racer in Canada. Thus, little is known about the ecology of this species at the northern extent of its geographic range. The bullsnake (Pituophis catenifer sayi) is sympatric with the eastern yellow-bellied racer over its Canadian range, and shares habitat and hibernacula. The geographic range of the bullsnake in Canada is broader than that of the racer, but little information is available on habitat requirements of this species. As a consequence, the bullsnake has a conservation status of "Data Deficient". I used radio-telemetry to examine movement patterns and habitat selection of racers and bullsnakes in southern Saskatchewan. Over two years I tracked 19 racers and 16 bullsnakes from 4 hibernacula in the Grasslands National Park area. At each location used by a snake, I quantified macrohabitat type and a suite of microhabitat features. I totalled the proportion of time spent on each macrohabitat type by each species and compared it to the proportion of that macrohabitat available. I incorporated microhabitat variables into multivariate habitat selection models. One hundred percent Minimum Convex Polygon home ranges were calculated for each individual, as well as the maximum dispersal distances and the average length of daily movements. I found that both species occupied larger home ranges and travelled farther than previously studied populations in more southerly locations in the United States. The average maximum distance traveled by racers was 2551.3 m from their den, while bullsnakes traveled an average maximum distance of 1708.8 m from their den. Racers used habitat near rivers 5 times more often than would be expected based on the availability of that macrohabitat, while bullsnakes selected lowland pasture 3 times more often and road areas 4 times more often than would be expected based on availability. At the microhabitat level of selection, both racers and bullsnakes selected to be at burrows (0 -- 1 m from a burrow) most frequently. Shrub cover and vegetation density also positively affected the probability of habitat use by racers. I conclude that the most important habitat for eastern yellow-bellied racers appears to be within 5 km of their den. Specifically they need riparian areas with many sites for refuge, including shrubby vegetation cover and burrows. Bullsnakes rely on habitat within 4 km of their den sites, using burrows in lowland pastures and road areas.