An Infrared Thermographic Study of Surface Temperature in Relation to External Thermal Stress in Three Species of Foxes: The Red Fox (<i>Vulpes vulpes</i>), Arctic Fox (<i>Alopex lagopus</i>), and Kit Fox (<i>Vulpes macrotis</i>)

Abstract

Temperatures of different body surface regions of unrestrained adult red, arctic, and kit foxes exposed to ambient temperatures (Ta) ranging from -25° to 33° C were measured by infrared (IR) thermography. Foxes are able to regulate heat exchange with their environment by controlling the temperature of the body surface. At Ta's well below zero, they are able to maintain all exposed surfaces above the freezing point by vasodilation and increased blood flow into these surface areas. The important thermoregulatory surfaces include the area of the face, nose, dorsal head, pinna, lower legs, and paws in red and kit foxes, and the face, nose, front of the pinna, lower legs, and paws in arctic foxes. All these thermoregulatory effective surface areas are covered with relatively short fur during all seasons. The lower legs and paws are the most effective surfaces. The surfaces involved in active heat loss seem to be nearly the same in all foxes. However, there are significant interspecific differences in the relative size of these surfaces, which are relatively large in kit foxes, small in arctic foxes, and intermediate in red foxes. Foxes use the nose for evaporative cooling, and it is probably a part of a brain-cooling mechanism similar to that described in dogs.