| Summary: | The main objective of this study was to develop a model of the thermoregulatory control system which could be used to predict the responses of unrestrained foxes of different species to naturally occurring thermal stress. The studied species included the red fox (Vulpes vulpes), arctic fox (Alopex lagopus), and kit fox (Vulpes macrotis). The model was used to test hypothesis whether species of foxes occupying different habitats do or do not use the same thermoregulatory control system. First, infrared (IR) thermography was used to study the control of surface temperature in undisturbed foxes exposed to naturally occurring thermal stress. The resting metabolic rate (RMR) and evaporative water loss (EWL) in the red and arctic fox was measured as oxygen consumption at various ambient temperatures (T$\sb{\rm a}$) using metabolic chamber. Total heat flow from the animal's surface (Q$\sb{\rm t}$) was calculated using the surface temperature measurements. Second, red foxes were surgically implanted in the POAH with two thermodes to control the temperatures of this region. The temperature of the POAH (T$\sb{\rm poah}$) was monitored with an implanted thermocouple. Deep body temperature (T$\sb{\rm b}$), surface temperature, and metabolic rate (MR) were measured. The animals were exposed to various T$\sb{\rm a}$ in a temperature chamber. The most important thermoregulatory surfaces include the area of the dorsal head, face, nose, pinna, lower legs, and paws in the red and kit fox, and the face, nose, front of the pinna, lower legs, and paws in the arctic fox. Although the thermoregulatory effective surface areas represent only about 30% of the total surface area, the animals can lose more than 70% of the total radiative and convective heat loss through these areas. These surfaces are relatively large in the kit fox, small in the arctic fox, and intermediate in the red fox. MR increased during both heating and cooling of the POAH. Resting T$\sb{\rm poah}$ was lower than T$\sb{\rm b}$ at all temperatures which indicates ...
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