IDENTIFYING ECOHYDROLOGICAL CONTROLS ON THE SPATIOTEMPORAL VARIABILITY AND RESILIENCE OF EASTERN MASSASAUGA RATTLESNAKE (SISTRURUS CATENATUS) PEATLAND OVERWINTERING HABITAT

Abstract

Herpetofauna at their northern range limit must seek refuge from harsh winters by selecting suitable overwintering habitat. In the Eastern Georgian Bay region of Ontario, semi-aquatic reptiles such as the Eastern Massasauga rattlesnake (Sistrurus catenatus) often overwinter in raised peatland hummocks which can avoid prolonged periods of flooding while having great insulating properties and suitable moisture conditions due to proximity to the water table. However, climate change threatens the persistence of suitable overwintering conditions in hummock hibernacula due to changing winter weather conditions. We monitored overwintering conditions in 10 Eastern Georgian Bay peatlands for six winters from 2018–2024 by tracking the life or resilience zone - the space above the water table and below the 0 °C isotherm. We monitored micrometeorological variables to identify their influence on resilience zone dynamics and predicted how resilience zone dynamics would change under different climate change scenarios based on the IPCC’s shared socioeconomic pathways (SSPs). We predicted that both water tables and 0 °C isotherms would rise under SSP2-4.5 and SSP5-8.5, though some peatlands were predicted to experience a drop in water table position, and the degree of 0 °C isotherm rise differed by peatland. This highlights that some peatlands exhibit greater resilience against climate change compared to others which has implications for the future availability of suitable snake overwintering habitat. We also tested the influence of site-specific characteristics on overwintering conditions. At the microhabitat scale, hummock height and shrub cover were associated with resilience zone size and availability and at the macrohabitat scale, smaller peatlands with proportionally small watersheds and large outflows were associated with suitable overwintering conditions. This research contributes to our understanding of ecohydrological influences on massasauga overwintering conditions across spatial scales and highlights the importance of considering habitat ecohydrology for effective habitat conservation.