Factors influencing resting metabolic rate and evaporative water loss rate in Pygmy Rattlesnakes (Sistrurus miliarius)

Agugliaro, Joseph

jaguglia@fdu.edu

Department of Biological Sciences

Fairleigh Dickinson University

Madison, New Jersey USA

Lind, Craig M.

Department of Natural Sciences and Mathematics

Stockton University

Galloway, New Jersey USA

Farrell, Terence M.

Department of Biology

Stetson University

DeLand, Florida USA

A central goal in physiological ecology is to understand the intrinsic and extrinsic factors that influence the allocation of available resources (such as energy and water) to competing physiological functions, and how the allocation “decisions” of individuals may in turn influence fitness and population persistence. Pygmy Rattlesnakes (Sistrurus miliarius) in central Florida are locally abundant and surface active year-round, making them well-suited for physiological sampling of field-acclimatized individuals in this context. Since winter 2017-2018, we have measured resting metabolic rate (RMR, as CO2 production rate) and total evaporative water loss rate (EWL) of over 200 S. miliarius via flow-through respirometry. Our work began by investigating the energetic and hydric consequences of an endemic mycotic disease (snake fungal disease or ophidiomycosis) naturally afflicting snakes in our study population. Ongoing sampling of RMR and EWL continues to shed light on a number of factors influencing the energy and water budgets of S. miliarius. We additionally report on progress made assessing the following: thermal sensitivity and allometric scaling of RMR; season variation in RMR and EWL; effects of reproductive and disease status on the cost of mounting an immune response to a bacterial antigen; the metabolic cost of pregnancy; and the repeatability of RMR. Our work demonstrates how measurements of the energy and water relations of pitvipers provide valuable information that may inform conservation efforts.