Massassauga Rattlesnake Overwintering Lifezone

/ gtattersall

Congratulations to lab member, Anne Yagi on publishing a life’s work of research on the overwintering lifezone of the Eastern Massassauga rattlesnake! The final proofs have been sent back to the publisher and we are anxiously awaiting it to make it to press:

Summary of the study here, with links to the paper below.

Temperate snakes occupy overwintering sites for most of their annual life cycle. Microhabitat characteristics of the hibernaculum are largely undescribed yet are paramount in ensuring snake overwintering survival.

We hypothesized that snakes survive hibernation within a vertical subterranean space that we termed a “life zone”, that is aerobic, flood, and frost-free throughout winter and did this by studying an isolated, endangered population of Massasaugas (Sistrurus catenatus) inhabiting an anthropogenically-altered peatland and monitored the subterranean habitat during a period of environmental stochasticity.

Lifezone concept (Credit: A Yagi)

Initial radio telemetry confirmed that snakes moved between altered and natural habitats during the active season and showed hibernation site fidelity to either habitat. We used a grid of groundwater wells, and frost tubes installed in each hibernation area to measure lifezone characteristics over 11 consecutive winters.

The lifezone within the impacted area was periodically reduced to zero during a flood-freeze cycle, while the lifezone in the natural area was maintained.

Sample figure from the paper showing year by year changes in the winter lifezone size (cm = depth or size underground that remains frost and flood free). Mined sites refer to an anthropogenically disturbed site where surface peat extraction had historically occurred. Unmined site is a peat bog. Flood events refer to a period of time when large regions of the site experienced sustained surface flooding.

Soil-depth and flood status best predicted lifezone size. Thermal buffering and groundwater dissolved oxygen increased with lifezone size, and annual Massasauga encounters were significantly correlated with lifezone size.

This analysis suggests a population decline occurred when lifezone size was reduced by flooding. Our data give support to the importance and maintenance of a lifezone for successful snake hibernation.

Our methods apply to subterranean hibernation habitats that are at risk of environmental stochasticity, causing flooding, freezing, or hypoxia, and speak to the issues regarding management of sensitive watersheds inhabitated by species-at-risk.

Measuring the lifezone.
Snake well installation in the field to test the overwintering lifezone.

Citation

Yagi, A, Planck, RJ, Yagi, KT, and Tattersall GJ. 2020. A long-term study on Massasaugas (Sistrurus catenatus) inhabiting a partially-mined peatland: presenting a standardized method to characterize snake overwintering habitat. Journal of Herpetology. 54: 235-244. https://journalofherpetology.org/doi/full/10.1670/18-143

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