Movement And Habitat Use Of The Great Basin Spadefoot Spea Intermontana At Its Northern Range Limit PDF Download

The distribution of resources determines space use and habitat selection by snakes. Particularly in northern areas, the proximity of overwintering den sites to summering habitat likely influences space use. The resources driving seasonal movements among habitats may vary among populations and thus, space and habitat requirements may also vary. In addition, human modification may affect resource use by altering available habitats and resources. Although previous studies have reported differences in spatial ecology among populations, the driving factors of this variation remain to be addressed for many species. Bullsnakes (Pituophis catenifer sayi) reach their northern range limits in southern Saskatchewan, where they are currently listed as Data Deficient by the Committee on the Status of Endangered Wildlife in Canada. Many studies have focused on core range areas, while northern studies have focused on one population in the Frenchman River Valley, Saskatchewan. The habitat and space requirements identified in these previous studies, however, may not be relevant to all bullsnake populations. I examined bullsnake space and habitat use among independent populations in three river valleys (Frenchman River, South Saskatchewan River, and Big Muddy Valleys) in Saskatchewan, with varying habitat types (natural and anthropogenic) and availability. I tracked bullsnakes using radio-telemetry, estimated home range areas and movement patterns, and measured third and fourth order habitat selection. The objectives of my research were (1) to examine the extent to which habitat selection and space use may vary among populations and (2) to identify important habitat features in common among snakes from different populations. Saskatchewan bullsnakes demonstrated variable space use and movement patterns among populations, exceeding space use requirements previously observed in southern areas. One population (Big Muddy Valley), on average, used 2.7 to 3 times less space, travelled 2.3 to 2.7 times shorter distances from overwintering sites, and had greater home range overlap than snakes from the other populations (Frenchman and South Saskatchewan River Valleys). This suggests that bullsnakes in the Big Muddy Valley had a closer spatial association between seasonal habitats. Bullsnakes appear to be flexible in terms of their third order habitat selection. Native habitats were used as expected across all valleys, but human-modified habitats were used at different frequencies across populations. These differences in habitat selection among populations are most likely due to differences in habitat availability among landscapes. Fourth habitat selection, however, was similar among populations, with bullsnakes selecting for sites typically within 1 m of a refuge site (including burrows, cement pads, and rock piles). It appears that bullsnakes occupy variable-sized home ranges and move variable distances. Bullsnakes also appear to be flexible in terms of how they meet resource requirements across their geographic range via habitat selection at a broad spatial scale. My study did find, however, that at a fine spatial scale refuge sites are an important habitat feature for bullsnakes. Conservation and management strategies are typically broad and are implemented as if populations of the same species have similar habitat requirements. However, my results indicate that this is not the case. As such, management plans may not be applicable to all populations.