Comparison of Body Temperatures Across Physiological States in Syntopic Snake Species (Thamnophis sirtalis and Nerodia sipedon) from Pennsylvania

Daniel F. Hughes^1,*, Pablo R. Delis², and Walter E. Meshaka Jr.³

¹Department of Animal Sciences and Department of Agriculture and Biological Engineering, University of Illinois at Urbana-Champaign, 1304 West Pennsylvania Avenue, Urbana, IL 61801. ²Department of Biology, Shippensburg University, 1871 Old Main Drive, Shippensburg, PA 17257. ³Section of Zoology and Botany, State Museum of Pennsylvania, 300 North Street, Harrisburg, PA 17120. *Corresponding author.

Northeastern Naturalist, Volume 26, Issue 4 (2019): 749–760

Abstract
Physiological states in snakes, such as digestion, gestation, and ecdysis, have been associated with different body temperatures (BT), yet few studies have examined these associations in a comparative context for wild-caught animals. We collected body and environmental temperatures for 2 natricine snake species—Thamnophis sirtalis (Common Gartersnake) and Nerodia sipedon (Common Watersnake)—from 4 artificial wetlands at the Letterkenny Army Depot, Franklin County, PA. We measured thermal data and associated microclimates from snakes captured under tin cover boards during monthly searches from Spring to Fall of 2012 (April–October). From 47 Common Gartersnakes and 20 Common Watersnakes, we found that most individuals of both species had a BT between 20 and 30 °C, which is consistent with data from other populations. Inter- and intraspecific comparisons of snake BTs in different physiological states revealed that Common Gartersnakes operated at higher temperatures than Common Watersnakes. Common Watersnakes thermoregulated within a generally narrower range of temperatures than Common Gartersnakes. The wide-ranging thermal ecology of the Common Gartersnake may facilitate its flexibility to occupy many habitats across an extensive geographic distribution and perhaps predispose it to greater adaptability in a changing thermal environment. We summarize our data on snake BTs and their associations with relevant environmental temperatures, discuss snake BT ranges across distinct physiological groups, and compare our results to those of other snake populations. Our findings provide a baseline to understand the degree to which operating snake temperatures, and consequently physiological processes, will change because of future warming in the Northeast.

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