Thermal ecology of Northern Water Snakes (Nerodia sipedon) in a northern wetland in central Michigan

John W Rowe; Tyler M Goerge; Chelsea E Martin; William P Mulligan

doi:10.1016/j.jtherbio.2022.103204

Thermal ecology of Northern Water Snakes (Nerodia sipedon) in a northern wetland in central Michigan

J Therm Biol. 2022 Apr:105:103204. doi: 10.1016/j.jtherbio.2022.103204. Epub 2022 Feb 4.

Authors

John W Rowe¹, Tyler M Goerge², Chelsea E Martin³, William P Mulligan⁴

Affiliations

¹ Biology Department, Alma College, 614 West Superior Street, Alma, MI, 48801, USA. Electronic address: rowe@alma.edu.
² Biology Department, Alma College, 614 West Superior Street, Alma, MI, 48801, USA; Department of Biological Sciences, Life Sciences Building 141, Ohio University, Athens, OH, 45701, USA.
³ Biology Department, Alma College, 614 West Superior Street, Alma, MI, 48801, USA; Earth and Biological Sciences, Loma Linda University, 11175 Campus Street, Loma Linda, CA, 92350, USA.
⁴ Biology Department, Alma College, 614 West Superior Street, Alma, MI, 48801, USA; Robert B. Annis Water Resources Institute, Grand Valley State University, 1 Campus Drive, Allendale, MI, 49401-9403, USA.

PMID: 35393045
DOI: 10.1016/j.jtherbio.2022.103204

Abstract

Semi-aquatic north-temperate reptiles experience challenging environmental conditions for thermoregulation on both seasonal and daily bases. We studied the thermal biology of north-temperate Northern Water Snakes (Nerodia sipedon) in central Michigan by remote radiotelemetry monitoring of snake body temperature (T_b) using surgically implanted thermally-sensitive radio-transmitters and by measuring operative temperatures (T_e) across a range of microhabitats using biophysical models. Our goals included evaluation of thermoregulatory capabilities at a locality that we viewed to be a fine-grained thermal environment, seasonal variations in patterns of thermoregulation, and the effects of sex on thermoregulation. During summer, snakes showed diel T_b cycling apparently using the open Sphagnum mat for late morning warming and shuttling among different microhabitats until early evening when a monotonic decline in T_b ensued and continued through the early morning hours. Snakes attained T_b within their laboratory-determined preferred body temperature range (T_set = 28-33 °C) mostly during late afternoon and with average percentages of T_b values for individual snakes within T_set range when permitted by operative temperatures (E_x) between 68 and 70% of the time depending on method of measurement. Relatively high investment in thermoregulation when thermal conditions were poor occurred only during September but declined thereafter as snakes prepared to overwinter. We did not detect differences in thermoregulation among reproductive females, non-reproductive females, and males. Relative to a population of N. sipedon at a higher latitude in Ontario our snakes showed a relatively high T_set range and thermoregulated more effectively, particularly during the daylight hours. It remains unclear how much inter-population variation in thermoregulation is due to potential adaptations to latitude, to habitat differences, or variations in methodologies.

Keywords: Nerodia; Snakes; Thermoregulation.

MeSH terms

Animals
Body Temperature Regulation / physiology
Colubridae*
Female
Male
Michigan
Seasons
Snakes
Wetlands