critical temperature of the Arctic fox is at in the winter and in the summer. It was commonly believed that the Arctic fox had a lower critical temperature below . However, some scientists have concluded that this statistic is not accurate since it was never tested using the proper equipment. About 22% of the total body surface area of the Arctic fox dissipates heat readily compared to red foxes at 33%. The regions that have the greatest heat loss are the nose, ears, legs, and feet, which is useful in the summer for thermal heat regulation. Also, the Arctic fox has a beneficial mechanism in their nose for evaporative cooling like dogs, which keeps the brain cool during the summer and exercise. The thermal conductivity of Arctic fox fur in the summer and winter is the same; however, the thermal conductance of the Arctic fox in the winter is lower than the summer since fur thickness increases by 140%. In the summer, the thermal conductance of the Arctic foxes body is 114% higher than the winter, but their body core temperature is constant year-round. One way that Arctic foxes regulate their body temperature is by utilizing a countercurrent heat exchange in the blood of their legs. Arctic foxes can constantly keep their feet above the tissue freezing point () when standing on cold substrates without losing mobility or feeling pain. They do this by increasing vasodilation and blood flow to a capillary rete in the pad surface, which is in direct contact with the snow rather than the entire foot. They selectively vasoconstrict blood vessels in the center of the foot pad, which conserves energy and minimizes heat loss. Arctic foxes maintain the temperature in their paws independently from the core temperature. If the core temperature drops, the pad of the foot will remain constantly above the tissue freezing point. Size The average head-and-body length of the male is , with a range of , while the female averages with a range of . In some regions, no difference in size is seen between males and females. The tail is about long in both sexes. The height at the shoulder is . On average males weigh , with a range of , while females average , with a range of . Taxonomy Vulpes lagopus is a 'true fox' belonging to the genus Vulpes of the fox tribe Vulpini, which consists