Mention Arctic land mammals and the image of large, well-insulated creatures comes to mind: polar bears, musk ox, caribou and the extinct woolly mammoth, to name a few. But the small Arctic fox, the most northern-living canine on our planet, has managed to thrive on the harsh, treeless tundra of the Arctic biome. Equipped with a compact body habitus, thick, dense fur, furred paws and changing coloration to blend with its environment, this hardy fox also has an exquisite sense of hearing for prey location, adapts well to an omniverous diet and produces large litters to sustain its population.
After breeding in late winter or early spring, the monogamous pair uses a large den network in which to raise its litter of 6 to 15 or more kits; the newborn fox will remain with their mother through the summer and, as with some other wild canines, a few yearlings often stay behind to assist with feeding and protecting their younger siblings. The diet of the Arctic fox is dominated by lemmings and other small mammals (including seal pups) but also includes berries, vegetation, carrion, birds, fish and the eggs of seabirds and waterfowl. When food is abundant, they will bury eggs or meat in the Arctic permafrost for consumption during the harsh months of winter.
Circumpolar in their distribution, the populations of Arctic fox are stable in most areas though they are endangered in Scandinavia due to overhunting. Having evolved late in the Pleistocene, about 250,000 years ago, they spread across northern oceans on the vast ice shelves of that Period and are the only mammal native to Iceland. Today, like many polar species, Arctic fox are threatened by global warming that is changing their habitat, altering their food supply and allowing dominant predators (such as red fox and gray wolves) to invade their territory.