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Edge-habitat Use by Northwestern Gartersnakes (Thamnophis ordinoides) in Saanich, British Columbia

Graham P. Dixon-MacCallum, Katie A.H. Bell, Patrick T. Gregory

Abstract


Understanding habitat requirements of species is fundamental for their conservation and urban parks can provide key habitat for species in otherwise disturbed settings. Northwestern Gartersnakes (Thamnophis ordinoides) are common in parks in Saanich, British Columbia, but their specific habitat requirements are poorly understood. Based on previous studies and thermoregulatory needs of snakes, we predicted that edges, particularly field margins, would be heavily used by active snakes. We therefore used surveys that focused on edges to find snakes and measured edge-habitat use by comparing habitat variables at locations where snakes were found to the same variables at nearby random locations. Habitat variables included composition and structure of vegetation, substrate temperature, aspect, and slope. Overall, litter depth, canopy cover, a lack of bare ground and woody vegetation were the most important habitat variables for determining where snakes were found. our results provide a preliminary assessment to improve our understanding of habitat use for this species. The abundance of snakes found while surveying edges supports our initial assumption that edges are important habitat features but more work is required using multiple survey methods to further test this hypothesis.


Keywords


Northwestern Gartersnake; Thamnophis ordinoides; urban wildlife; reptiles; transect surveys; matched-pairs logistic regression; British Columbia

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DOI: http://dx.doi.org/10.22621/cfn.v131i1.1751



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