High Thermal Quality Rookeries Facilitate High Thermoregulatory Accuracy in Pregnant Female Rattlesnakes

Authors

Haley A. Moniz, California Polytechnic State University, San Luis ObispoFollow
Jack Henry Buck, Dickinson CollegeFollow
Hayley L. Crowell, University of Michigan-Ann ArborFollow
Scott M. Goetz, United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center, Fort Collins, ColoradoFollow
Trevor D. Ruiz, California Polytechnic State University, San Luis ObispoFollow
Emily N. Taylor, California Polytechnic State University, San Luis ObispoFollow
Scott M. Bobacks, Dickinson CollegeFollow

Document Type

Article

Date of this Version

2024

Citation

Journal of Thermal Biology (2024) 124: 103948

doi: 10.1016/j.jtherbio.2024.103948

The raw and processed data required to reproduce the above findings are publicly archived on Zenodo (https://doi-org.libproxy.unl.edu/10.5281/zenodo.13177060), with code hosted on GitHub (https://github.com/ruizt/viridis).

Comments

United States government work

Abstract

Temperature is a primary factor influencing organismal development, and the fluctuating daily and seasonal thermal regimes of temperate climates may challenge the ability of viviparous reptiles to optimize body temperatures during gestation. Testing how viviparous reptiles navigate highly variable thermal conditions (e.g., relatively cold nights and/or highly fluctuating temperatures) is a powerful way to understand how they use microhabitats for thermoregulatory benefits. We assessed the thermal ecology of pregnant and non-pregnant female prairie rattlesnakes (Crotalus viridis) inhabiting a high-elevation, montane shrubland in northwest Colorado throughout their short summer active season, addressing the thermal consequences of microhabitat selection with a focus on thermoregulation of pregnant females at communal rookery sites. We deployed operative temperature models to collect data on the thermal quality of microhabitats used by the snakes, and calculated thermoregulatory accuracy of the snakes by comparing their field-active body temperatures with preferred body temperatures of snakes placed in a thermal gradient. Pregnant females inhabited rocky, hilltop rookeries that had higher thermal quality due to higher and less variable nighttime temperatures compared to microhabitats in the surrounding prairie. Pregnant females therefore thermoregulated more accurately than non-pregnant females. The difference was most pronounced during the night, when pregnant females at rookeries maintained higher body temperatures than non-pregnant snakes in the prairie. Our results support the hypothesis that one major reason female rattlesnakes at high latitudes and/or high elevations forgo migration and gestate at communal, rocky, hilltop rookeries is that, relative to prairie microhabitats, they provide better conditions for thermoregulation during pregnancy.