Arctic Fox

The Arctic fox is a mammal belonging to the Canidae family. They live in all arctic tundra habitats and sea ice in and around surrounding islands. They have a thick fur coat with hollow hair shafts that trap the warm air and keeps their body temperature at 104°F (40°C) and a tail that acts as a blanket to wrap around their body while they sleep. The Arctic foxes diet consists of small rodents like lemmings however they are omnivores and will eat whatever is available in times of need including polar bear excrement. If food is scarce the Arctic fox will dig a den and can slow its metabolism and heart rate for up to two weeks. Once their “hibernation” is complete they will emerge ready to hunt again. The Arctic fox is a very small mammal weighing 6–10 lb (~2.7–4.5 kg) and is the size of a cat. Their white fur provides excellent camouflage into their arctic environments during the winter months, as the snow melts a pigment called melanin provides the fox with its brown coat during the summer months. Their small compact bodies, unique fur coat, and varied diet allows the species to survive in the most extreme winters on the planet. A couple months before the end of winter the foxes will begin to mate, they get into pairs and live in dens for the 51–57 days of gestation. Arctic foxes give birth to a litter of about 7–10 pups and the pair stays together to raise the litter until fall when the family unit breaks up.

Arctic fox were occasionally eaten by Inuit and later became an important economic resource once trading posts were established. In the 1960’s the Arctic fox was an important resource and the Inuit would trade their pelts/fur and tails as neck warmers for cash from trading companies such as the Hudson Bay Trading Company. Inuit only used fox meat as an emergency source of meat when food was scarce. Inuit would follow the Arctic fox in order to help them locate food hidden deep beneath the snow. The Arctic fox is steeped in Indigenous folklore, the Dene first nations have a story in which the Arctic fox saves the people from starvation during barren times by following a raven and bringing the people caribou to feed on.

Arctic foxes have been listed as "least concern" by the IUCN red list; their current population trend is stable. Their world population is in the number of hundreds of thousands and fluctuates based on the amount of food (lemmings) during a season. The largest threat to the Arctic fox population was the overhunting due to fur trading, with the decline of the fur trade over the years the threat of over exploitation has diminished and populations are now stable. The biggest threat to the Arctic fox now is scarcity of prey and disease.

This highly adaptable arctic predator with a pan-Arctic distribution has been the subject of significant genomic scrutiny, in part because in some locations it is vulnerable to extirpation, or has been in the past (e.g., the Fennoscandinavian population); is, in some locations farmed and a source of income; and because Arctic terrestrial mammals are of keen interest for those with a penchant for studying evolution in the arena of the Arctic. As a result, whole genome sequences have been produced, including at the level of individual chromosomes (chromosomal-level genome sequencing).

Whole genome scans can reveal remarkable stories in which single genes can have a large impact on an animal’s physical form. A genome-wide association study (in which whole genomes are scanned for association with biological traits and/or environmental variables) identified a single gene – called MC1R – responsible for the coat colour in this species (including the ‘blue’ form that does not adopt a white pelage in the winter, instead retaining a dull grey or charcoal coat; the ‘white’ form represents > 90% of all arctic foxes). The difference in colour is due to different forms of the MC1R gene (called alleles), so that a when rare blue fur colour variation is present in an individual that animal always develops the blue colouration (in Mendelian genetics, this is termed a ‘dominant allele’). Most Arctic foxes have two copies of the white ‘recessive allele’. This study is a rare example of almost perfect Mendelian inheritance of a trait based on a single gene governing the expression of a discrete biological trait (fur colour). That the ‘blue’ form is relatively rare despite the dominance of the blue MC1R allele is possibly associated with blue foxes being less ‘fit’ (less liable to pass on their genes to the next generation) than white ones in locations where the white form has an advantage in winter (through increased ability to hide from both predators and prey).

The Arctic fox, although amenable to breeding in captive scenarios (e.g., farming), can suffer from the erosion of genomic variation over the generations from the result of a limited number of breeding individuals contributing to the gene pool. Genomics has revealed that in both intensively farmed populations and in insular populations (island inhabitants) in Fennoscandinavia, foxes have become very inbred resulting in individuals sharing large tracts of identical genetic variation (called ‘runs of homozygosity’). Such individuals are at risk of increased heritable diseases and reduced reproductive potential. However, transplanting more outbred foxes into the breeding population can be a means of providing genetic rescue. This has been shown to work for highly inbred populations of arctic foxes, where offspring are shown to recover some genetic variation compared to their inbred parent or grandparents.

The arctic fox, inhabiting a pivotal role in arctic conservation genomics, provides a window into applying genetic data from genomes in a way that that can have real impacts on the management of contemporary populations and on our understanding of the processes influencing the genetics and evolution of Arctic mammals.