Thermoregulation of the North American Mink during Rest and Activity in the Aquatic Environment

Abstract

Thermoregulation during swimming and resting in water was investigated for the North American mink (Mustela vision, Schreber) in summer and winter pelage by measuring total heat production, heat storage, and minimum thermal conductance. Swimming activity over the range of 0.13-0.60 m·s⁻¹ resulted in heat losses that exceeded metabolic heat production within 5 min of immersion. This imbalance, manifested as a decline in core body temperature (core Tb), resulted in negative levels of heat storage. Negative heat storage for mink was greatest at intermediate swimming speeds. Maximum levels were -14.28 W·kg⁻¹ at 0.29 m·s⁻¹ and -8.72 W·kg⁻¹ at 0.36 m·s⁻¹ for mink in summer and winter pelage, respectively. Thermal conductance determined from cooling curves of carcasses and a taxidermic mount increased linearly with water speed and was comparatively greater at all speeds for animals in summer pelage. Patterns of cooling for carcasses, the taxidermic mount, and swimming mink were similar. In combination with regional heterothermy and elevated heat production, insulation provided by an air layer pervading the fur will permit short bouts of swimming in which Tb is maintained by foraging mink.