Multi-Scale Patterns of Eastern Milksnake (Lampropeltis triangulum) Habitat Selection and Behavioural Responses to Habitat Fragmentation

Abstract

The decline of species with specific habitat needs can be attributed to human caused habitat destruction and fragmentation. This is particularly concerning for reptiles, as they are often unable to adapt to modified landscapes. The eastern milksnake (Lampropeltis triangulum) represents the rare case of a species at risk that has persisted both in disturbed and undisturbed landscapes throughout its historic Canadian range. However, a lack of contemporary occurrence data makes it difficult to assess the impact of perceived threats on the species, or devise effective conservation strategies. Here, I aim to quantify milksnake habitat selection and potential behavioural adaptation in response to human development at multiple spatial scales. Specifically, I address the questions 1) Do milksnakes modify behaviours (home range size, movement rates) in response to human modified landscapes? 2) Which habitats are milksnakes selecting for at the home range scale, and within the home range, which microhabitat features are selected for? And 3) How does landscape scale habitat fragmentation impact milksnake distribution? I used radio telemetry to track 17 individuals between 2015 and 2017 in Rouge National Urban Park, and used a large scale coverboard survey to generate occurrence records across the Credit Valley and Toronto Region Conservation Authority Management Areas. Using this data, I analyzed movement rates, assessed the degree of road avoidance, determined home range sizes, and compared these metrics to a natural site. I then analyzed home range scale habitat selection, and determined which microhabitats features are selected for within home ranges. Using occurrence data, I determined best predicted landscape scale habitat for milksnakes, and compared this to a generalist species. Results indicate that milksnakes are modifying behaviours in urban landscapes, as they have significantly higher movement rates and avoid road crossings. Milksnakes are also avoiding human modified landcover types (urban area and agriculture) at all scales. At the home range and microhabitat scales, milksnakes are selecting a variety of open habitats with abundant cover, while selection at the landscape scale favours large habitat patches. In order to conserve snake populations, I recommend that conservation of large natural areas and the establishment of corridors connecting them are prioritized.