Metabolic and behavioral responses of muskrats (Ondatra zibethicus) to elevated CO2 in a simulated winter microhabitat

Abstract

Metabolic and behavioral responses to inspired CO2 were investigated in muskrats housed in a microhabitat designed to simulate winter field conditions. Mean daily rate of oxygen consumption [Formula: see text] declined from 1.46 mL O2∙g∙h−1 in animals breathing room air to 1.11–1.25 mL O2∙g∙h−1 in animals inhaling 4–10% CO2 in the simulated lodge. Daily patterns of [Formula: see text], abdominal body temperature (Tb), and foraging activity were minimally affected by chronic CO2 exposure, though muskrats breathing 9–10% CO2 made shorter voluntary dives. The ability of muskrats to rewarm following foraging activity was slightly depressed by hypercapnia. Abrupt exposure of resting animals to ambient CO2 levels of 10–16% often elicited avoidance reactions in the absence of any apparent change in [Formula: see text] or Tb. This study provides the first demonstration of behavioral and metabolic responses by muskrats to CO2 levels encountered in the winter microhabitat of this species.