Arctic fox in a winter fur coat
Basic information about Arctic foxes
Average Weight: 3 to 8kg (6.5-17 lbs). Average Length: 75 to 110 cm long (2.3-3.5 feet) including a tail of around 30cm (12 inches), 20 to 30cm (9-12 inches) tall at the shoulder, females slightly smaller than males
Breeding Season: Arctic foxes form monogamous pairs through a breeding season (April to May) though often several females will live together in a large and complex den that can be many years old, even centuries. Typically they have litters of 5 to 8 but may be as many as 25, the most of any carnivore. Sometimes young non-breeding foxes will live in the den too and help to raise the pups from the following year.
Estimated world population: – Several hundred thousand, wide fluctuations as a result of varying prey numbers and a rapid ability to reproduce.
Diet: A wide range of foods, the main prey is lemmings, they will hunt and catch other small animals and will also scavenge food from beneath sea-bird colonies on cliffs and left overs from predators such as polar bears. They will take eggs where possible from tundra nesting birds, though are not entirely carnivorous also eating berries and seaweed when available.
A family of foxes can get through several dozen lemmings in a day. They will eat young ringed seals when they are vulnerable in the snow den shortly after they are born in the same manner that they attack lemmings beneath the snow, detecting them by sound and then jumping on and punching through the covering snow layer.
Conservation status: Least Concern.
Habitat and Distribution: The Arctic Fox lives its whole life above the northern tree line in the Arctic tundra, it has found its way to most Arctic islands and is the only mammal native to Iceland. It may be found on the sea-ice in winter as it extends its foraging range. The southern limit of the arctic fox is partially dictated by the presence of red foxes which out-compete arctic foxes in areas where tundra turns to shrubs and trees.
Predators: Polar bears, wolverines, red foxes and golden eagles. They have been and continue to be trapped for their thick winter coats in particular.
What are Arctic Foxes like? What adaptations do they have?
Distribution range of the Arctic Fox
They survive in some of the coldest places on earth which is no mean feat for such a relatively small animal, they have a number of anatomical, behavioural and physiological adaptations that allow them to do this successfully.
Arctic Fox Adaptations:
Relatively low surface area to volume ratio (anatomical) – Compared to other species of fox, arctic foxes have proportionally shorter legs, shorter necks and smaller ears. This means that there is less surface area to lose heat from compared to more slender southern foxes.
Thick camouflaged seasonal fur (anatomical): The coat of the arctic fox is always thick and highly insulating. They grow two rather distinct versions over the course of a year however. The summer coat is thinner and dark grey to a brown, the colour allowing it to be camouflaged against the darker background of rock and vegetation when the ice and snow of winter have melted. The luxurious winter coat is very thick making the fox look more rounded and is white so camouflaging it against an icy background.
Thick fur on the tail (anatomical) – The tail acts to provide extra insulation when it is needed. When the fox is active and generating heat it is out of the way, while when the fox curls up to sleep or to keep warm in extreme cold, the tail fur can brought into play for extra wrap around insulation.
Thick fur on the paws (anatomical) – to insulate them from snow and ice and also provide for grip on slippery surfaces. Thick layer of body fat (anatomical / physiological) – for insulation and food storage to help survive the winter when food supply may be intermittent.
Countercurrent heat exchanger in the paws (anatomical/physiological) – Along with many other animals including domestic dogs, there is a mechanism in the paws of arctic foxes that keeps them at a lower temperature than the body core so minimizing heat loss via this extremity that is in contact with the ground. Blood entering the paws is used to heat up blood that is leaving, this prevents the core from being cooled by heat loss at the extremities. Similar mechanisms are also found in the feet of birds such as ducks and penguins.
Shelter in burrows they dig into the snow during blizzards and very cold weather (behavioral) – A relatively quick and easy way of avoiding the worst of the weather by tunneling beneath the snow to avoid the biting wind and gain extra insulation from the snow. While the temperature in the snow hole is still below freezing, it can be much higher than outside the snow hole.
Large litter sizes in years with high prey populations (physiological) – The population size of arctic foxes is tied very closely to the population size of its prey which consists largely of lemmings. Lemmings can breed very quickly in good conditions though are short-lived, the ability of the arctic fox to keep up with their reproductive rate to some degree gives them the ability to take advantage of productive years before it is too late. Typically an arctic fox will have between 5 and 9 pups, but have been recorded as high as 25, the most for any carnivore.
Very keen sense of hearing (anatomical/physiological) – Though small, the ears of arctic foxes are pointed forwards and so are very directional. They can hear their main prey, lemmings, moving through tunnels they make in the snow allowing the fox to pounce on the area where the sound is coming from without needing to see the prey and with the prey unaware that the fox is about to pounce.
