Our new paper, led by MSc student Harry Kumbhani and building on fieldwork conducted by former MSc student Curtis Abney, explores how Eastern Garter Snakes (Figure 1) navigate the complex thermal landscapes of wetlands in southern Ontario. Using detailed operative temperature models, which were copper snake replicas equipped with temperature loggers, our team quantified how three adjacent habitat types (closed forest, mixed shrub, and open peat; Figure 2) differ in the thermal opportunities they provide. Although the open peat habitat consistently reached the warmest temperatures and offered the greatest access to the snakes’ preferred thermal range, it also exhibited extreme highs that frequently exceeded the species’ upper thermal tolerance. This created a paradox: the habitat with the highest apparent thermal quality was also the riskiest.

Despite expectations that snakes might favour the warmest habitat, we found that Eastern Garter Snakes were most abundant in the intermediate, mixed-shrub habitat, a pattern we describe as a “Goldilocks effect.” This middle habitat provided a balance of sun and shade, offering both basking opportunities and safe retreat sites, and avoided the thermal instability and overheating risk found in the open peat. The study suggests that thermal quality is more nuanced than simply being warm enough; stability, heterogeneity, and safety from extreme temperatures all shape how snakes use their environment. These findings highlight the importance of structurally diverse habitats for temperate reptiles and offer valuable insights into how changing landscapes may influence thermoregulation and habitat choice in the future.

Citation

Kumbhani, HAW, Abney, CR, Giacometti, D, and Tattersall, GJ. 2025. Operative temperatures of Eastern Garter Snakes (Thamnophis sirtalis sirtalis) reveal a Goldilocks effect for habitat use. Canadian Journal of Zoology, 103: 1-15. https://doi.org/10.1139/cjz-2025-0090