Forced Hibernation: Biologist's Toolkit

by ANNE YAGI

Anne is studying winter hibernation in gartersnakes and Massasauga rattlers. Her toolkit for species-at-risk recovery includes "forced hibernation" to improve overwinter survival of young snakes. Ξ Ontario, Canada

Temperate snakes spend more than half their life cycle sequestered underground within their hibernacula or den site.

The neonatal life stage is highly vulnerable to harsh overwintering conditions in many reptile species.

Using a population of wetland adapted snakes living in a partially-degraded habitat, we set out to determine where neonatal snakes are most likely to survive various winter conditions.

Over three winters, we used a “forced hibernation” technique, placing juvenile and neonatal Eastern Gartersnakes (Thamnophis s. sirtalis) and neonatal Massasauga Rattlesnakes (Sistrurus c. catenatus) into artificial vertical subterranean burrows.

The first two winters resulted in 97% survival of all gartersnakes (1 died via shrew predation), and the third year resulted in an overall 95% survival rate (1 Massasauga died by unknown causes).

Our results support our theory that successful snake hibernation requires the continuous presence of a “life zone” that does not flood or freeze completely.

Reptiles require environmental cues such as temperature and moisture gradients to locate suitable habitats to complete their annual life cycle.

Anthropogenically altered habitats including partially mined peatlands, agricultural fields, and road surfaces, mimic these cues and attract such temperaturedependent animals (i.e. ectotherms).

However, these altered habitats can act as an ecological trap where such habitats can leave individuals exposed to predators and unfavorable abiotic conditions like extreme thermal fluctuations, ultimately causing an increase in mortality risk.

Ecological trap theory suggests that the continued presence of a trap will drive populations to extinction. I have collected evidence supporting this theory since 1998, including results from radio telemetry and mark-recapture studies, thermal selection studies, assessments of wintering habitat conditions, and continuous mortality observations after wildfires and all types of winters.

The implications of ecological trap theory are particularly important at my study site, a partially-mined peatland, which has a resident reptile community that includes 5 species at risk.

The next phase of this project is to determine refugia needs for turtles and implement forced hibernation for various snake species until the ecological traps are mitigated and the species-at-risk populations are recovering.

Anne Yagi is a biologist based in Ontario, Canada. Her longterm research on subterranean ecology of reptiles is a collaboration with Dr. Glenn Tattersall and Dr. R. Jon Planck. Connect with Anne on Research Gate, LinkedIn, and her website www.8trees.ca

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