Most cold-tolerant canid

The most cold-tolerant canid is the Arctic fox (Vulpes lagopus), native to the Arctic regions of Europe, Asia and North America, including Iceland, northern Norway, Russia, Canada, Alaska and Greenland. Here, it can withstand environmental temperatures as low as -70°C (-94°F); under humane experimental conditions, captive specimens have even withstood temperatures as low as -80°C (-112°F). It is able to survive such extremes of cold due to a suite of morphological and physiological adaptations, including an extra-dense, multi-layered pelage, short limbs and muzzle that release less body heat that longer limbs and muzzle would do, plus the ability to reduce blood flow into its feet and toes, thereby preventing them from becoming frostbitten.

Although the Arctic fox is most commonly thought of as being pure white in fur colour, in reality this is only true of its winter coat, which enables it to blend in with the surrounding winter snow as camouflage from larger predators and serves as disguise when pursuing its own prey. During the summer, however, its coat changes colour, becoming brown dorsally and grey laterally. In addition, about 1% of Arctic foxes never develop their species' typical white winter coat, remaining bluish-brown all year long due to the expression of a rare mutant gene form – these aberrant Arctic foxes are known as "blue foxes".