Environmental and energetic constraints on effective thermal disease coping mechanisms in pitvipers
Lind, Craig M.
School of Natural Science and Mathematics
Stockton University
Galloway, New Jersey USA
Agugliaro, Joseph
Department of Biological Sciences
Fairleigh Dickinson University
Madison, New Jersey USA
Ortega, Jason
Biological Sciences Department University of Arkansas – Fort Smith
Fort Smith, Arkansas USA
Farrell, Terence M.
Department of Biology
Stetson University
DeLand, Florida USA
Emerging and opportunistic mycoses threaten North American pitviper populations. As ectothermic, low-energy specialists, the thermal coping strategies (e.g. fever) used by pitvipers are constrained by available environmental temperatures and the energetic costs associated with behavioral thermoregulation. Constraints on effective thermal coping strategies are poorly understood but may underly patterns of disease risk and outcomes for populations. We have studied thermal coping strategies in Pygmy Rattlesnakes (Sistrurus miliarius) afflicted with ophidiomycosis and held in outdoor mesocosms in Central FL. Outdoor mesocosms allowed us to quantify thermal coping strategies in operative thermal environments that exhibit natural daily and seasonal variation. We used thermal reaction norms for resting metabolic rate and innate immune performance to quantify the energetic cost and immune benefit of host thermal coping strategies in winter and summer. In both seasons, snakes afflicted with ophidiomycosis exhibited behavioral fever. The energetic costs of fever were sensitive to daily weather patterns and varied seasonally. The cost of fever was higher as a percentage of the resting energy budget in winter compared to summer. Modeled effects of host body temperature on innate immune performance also exhibited daily and seasonal variation. Immune performance was higher and less sensitive to fever in summer compared to winter. Together, environmental and energetic constraints on thermal coping mechanisms may explain seasonal patterns of disease prevalence/severity and body condition in Pygmy Rattlesnakes and other pitvipers.