During midwinter, foxes lead a mostly solitary existence except when congregating at the carcasses of marine mammals, caribou, or reindeer. Arctic foxes attain sexual maturity at 9 to 10 months, but many die in their first year. In summer, arctic foxes feed primarily on small mammals, including lemmings and tundra voles. Foxes denning near rocky cliffs along the seacoast often depend heavily on nesting seabirds such as auklets, puffins, and murres. When food is plentiful, it is sometimes cached among boulders and in dens for later use.
Arctic foxes are omnivorous.
They sometimes eat berries, eggs, and scavenged remains of other animals. Many foxes venture out onto the sea ice during winter to eat the remains of seals killed by polar bears. Arctic foxes may move long distances over sea ice. A fox tagged along the coast of Russia was captured near Wainwright, Alaska, a year later. In areas where lemmings and voles are the most important summer prey, numbers of foxes often rise and fall with cyclic changes of their prey.