Natural and artificial hibernacula use by three sympatric snake species

Species that persist at higher latitudes require specialized adaptations to survive decreased temperatures, inclement weather, and reduced resource availability during winter. As ectotherms, the internal temperature of snakes is determined by their external environment. Thus, within temperate ranges, snakes rely on hibernacula that meet the structural, thermal, and humidity conditions needed to survive overwinter. The apparent scarcity of snake hibernacula in cooler climes makes understanding the selection of this critical habitat feature significant for conservation. I used a community of three sympatric snake species to explore how habitat features relate to the number of each species at hibernacula and determine how these species vary in their selection of overwintering habitat. Little to no measured habitat metrics effectively explained the detected number of Great Basin Gophersnakes (Pituophis catenifer deserticola), Western Yellowbellied Racers (Coluber constrictor mormon) and Western Rattlesnakes (Crotalus oreganus oreganus) at hibernacula. Further, I reveal that although these species share the same landscape and, in some cases, hibernacula, they are not selecting habitat in the same way. This variation in habitat selection aligned with differences in detected egress behaviour. Given the apparent scarcity of denning sites, one can theorize the tremendous impact on snake populations when they are destroyed. Constructing artificial hibernacula is one proposed conservation or mitigation measure to combat this loss. In this study, I used the creation of two artificial hibernacula following a disturbance event to (i) collect the internal temperature and humidity of the hibernacula and the internal temperatures of snakes and (ii) monitor the adoption of the main artificial hibernacula by the original cohort of displaced snakes. Both artificial hibernacula provided a range of thermal and humidity conditions, with temperature generally increasing with depth and distance to the hibernacula mouth. Internal hibernacula readings buffered against and were largely independent of external temperature fluctuations (including during a low of -30.4°C). Temperatures of overwintering Great Basin Gophersnakes within the main artificial hibernacula were comparable to those in natural hibernacula. In particular, the artificial hibernacula provided thermal microsites conducive to the survival of gophersnakes at depths ranging from 2.6 to 3.1m. Despite relocation efforts and six translocated snakes overwintering the first year, no translocated snake naturally adopted or returned to the main hibernacula two years post-disturbance. However, two newly identified snakes overwintered in the main hibernacula in the second winter. Overall, my thesis highlights distinct interspecific variations in behaviour and hibernacula selection. Such variation indicates that conservation efforts and impact assessments that use hibernacula ‘models’ from well-studied species (e.g., Western Rattlesnakes) to extrapolate to other species may be ineffective. I recommend larger protection at the landscape level to avoid future disturbance of these hard-to-identify critical habitat features. In cases of disturbances, I show that artificial hibernacula can be built to be conducive to survival. However, we caution against using these structures as mitigation measures due to the low uptake of focal individuals, at least in the short term. Future research is needed to understand the use of these artificial structures over a longer period of time.