THERMOREGULATION IN THE MUSKRAT (ONDATRA-ZIBETHICUS) - USE OF REGIONAL HETEROTHERMIA

1. 1. Regional heterothermia, metabolic rates, and whole-body insulation were studied in six muskrats (Ondatra zibethicus), restrained in air and in water at temperatures of 20, 25, and 30°C. 2. 2. Appendicular temperatures were found to approach ambient temperature at all temperatures in water and at 20 and 25°C in air. 3. 3. In air at 30°C, appendicular temperatures increased above ambient temperature after an average colonic temperature of 39°C was attained. 4. 4. High peripheral temperatures, due to vasodilation, decrease whole-body insulation and allow for increased heat dissipation, while peripheral temperatures approaching ambient temperature, resulting from vasoconstriction or counter-current heat exchange, increase whole-body insulation thus maximizing heat conservation. 5. 5. The causative factor for the differential responses of muskrats in air and water was considered to be the higher thermal conductivity of water. © 1979.