The Arctic Fox Alopex lagopus

By PhD Magnus Tannerfeldt

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The species

The arctic fox, also called the polar fox or the white fox, is a characteristic species of the Arctic. It is a small (3-5 kg) circumpolar, tundra-living canid. In many areas, it is the most abundant mammalian predator, affecting the breeding success of migrating birds and possibly also lemming cycles. It is itself the victim of predation, mainly from red fox Vulpes vulpes, wolf Canis lupus, wolverine Gulo gulo and golden eagle Aquila chrysaëtos. To the indigenous peoples, it is a source of fur, meat and mythology.

Arctic foxes are opportunistic and eat almost anything that is digestible. They feed on berries, seaweed, insects and larvae, birds and their eggs, fish, seal placentas, small mammals and carcasses of large mammals (Chesemore 1968, Hersteinsson and Macdonald 1982, 1996, Birks and Penford 1990). In the arctic fox’s Holarctic range, productivity is generally low but food resources can be extremely abundant in small patches and during short time periods. The dominant pattern in resource availability is determined by rodent fluctuations. In continental areas, the main prey species in summer are lemmings, Lemmus and Dicrostonyx spp., voles, Microtus and Clethrionomys spp., and carcasses of reindeer Rangifer tarandus. In winter, ptarmigans Lagopus mutus and L. lagopus are also important as food resources (Mac-pherson 1969, Kaikusalo and Angerbjörn 1995). Lemmings and voles have a cyclical pattern of abundance and changes in arctic fox numbers can be drastic between good and bad years. In some years, food for arctic foxes is abundant, large litters are common and the population size increases rapidly, only to crash one or two years later. These population cycles are typically repeated every 4 years. In ice-free coastal areas, arctic fox populations are instead sustained on more stable summer food resources. At bird cliffs and along shore lines, food is abundant during the months of arctic fox reproduction and population densities are relatively constant between years (Hersteinsson and Macdonald 1982, 1996).

Arctic fox dens are situated in frost-free ground, often low mounds or eskers in the open tundra, or in rock piles. The dens have 4–250 entrances and a system of tunnels covering about 30 square meters. Some dens have been used for centuries by generations of foxes. Arctic foxes can start breeding in their first year of life and are considered to be essentially monogamous, although they can increase group size at high population densities (Zetterberg 1953, Chesemore 1975, Hersteinsson 1992, Kruchenkova and Formozov 1995). Territories are maintained during the breeding season or sometimes all year round, with size and shape determined by food availability (Hersteinsson 1984, Angerbjörn et al. 1998). Young foxes that stay in their parent’s home range are usually not allowed to breed (Hersteinsson 1984, Frafjord 1991).

Mating usually occurs in April – May, and the young are born after a gestation time of 52 days. Reported litter size means at weaning range from 3 to 11 with a maximum litter size of 19, the largest litter size of all carnivores (Frafjord 1992, Ovsyanikov 1993, Tannerfeldt & Angerbjörn 1998). At the age of three to four weeks the young (called whelps, kits, pups or cubs) start to appear outside the den. The age at weaning varies from 5 to 9 weeks (Hersteinsson and Macdonald 1982, Garrott et al. 1984, Derefeldt 1996). The young gradually become independent during the following month. Some cubs may leave the den in their sixth week of life while others stay until early spring before they disperse (Frafjord 1992). Juvenile mortality is often very high and adult mortality is around 50% per year (Tannerfeldt & Angerbjörn 1996). The average life span for animals that reach adulthood is around three years.

The arctic fox occurs in two distinct colour morphs. One is called ‘white’ due to its almost pure white winter coat; in summer it turns brownish dorsally and whitish ventrally. The other morph, ‘blue’, is usually brown-bluish in winter and chocolate brown in summer. Within each morph there is considerable variation in appearance. Both morphs occur in almost all populations.

The arctic fox has many physical adaptations to the Arctic environment and they do not hibernate during the winter months. The fur of the arctic fox has the best insulative properties among all mammals and this animal does not under any naturally occurring temperatures need to increase metabolic rate to maintain homeothermy (Prestrud 1991). Arctic foxes change between summer and winter pelage and thereby adjust insulating properties and enhance camouflage. They further conserve body heat by having fur on the soles of their feet (Linnaeus named it lagopus, hare-foot), small ears, a short nose, and a well developed ability to reduce blood flow to peripheral regions of the body (Prestrud 1991, Klir and Heath 1992). In autumn, they can put on more than 50% of their body weight as fat for insulation and as energy reserves (Prestrud 1991).

The arctic fox is the only species in the genus Alopex, but recent studies have concluded that Alopex should be included in Vulpes to form a mono-phyletic group (Geffen et al. 1992, Angerbjörn and Kleist, unpublished data). Today, only three subspecies of the arctic fox are recognised, two of which are indigenous to the isolated Commander Islands (Ginsberg and Macdonald 1990).



The arctic fox is found in coastal and inland arctic and alpine tundra, in the arctic regions of Eurasia, North America, Greenland, and Iceland. Arctic foxes are capable of migrations of more than 1000 km in one season, and up to 2300 km in total (Pulliainen 1965, Chesemore 1968, Bannikov 1970, Eberhardt and Hanson 1978, Garrott and Eberhardt 1987). The species has spread to almost all Arctic land areas, including islands far away from the mainland, such as Iceland, Spitzbergen and the Novaya Zemlya, Pribilof, Commander and Wrangel Islands. Arctic foxes have been observed less than 60 km from the North Pole at 89°40’N (Andrey Masanov, pers. comm.).

It has been suggested that the southern limit of the arctic fox range is maintained by competition from the larger red fox, which in turn is has its northern limit determined by energetic requirements (Hersteinsson et al. 1989, Hersteinsson and Macdonald 1992).



As with many other game species, the best sources of historical and large scale population data are hunting bag records and questionnaires. There are several potential sources of error in such data collections (Garrott and Eberhardt 1987). In addition, numbers vary widely between years due to the large population fluctuations. However, the total population of arctic foxes must be in the order of several hundred thousand animals (Tannerfeldt 1997).

The world population is thus not endangered, but two arctic fox subpopulations are. One is the subspecies Alopex lagopus semenovi on Mednyi Island (Commander Islands, Russia), which was reduced by some 85-90%, to around 90 animals, as a result of mange caused by an ear tick introduced by dogs in the 1970’s (Goltsman et al. 1996). The population is currently under treatment with antiparasitic drugs, but the result is still uncertain.

The other threatened population is the one in Fennoscandia (Norway, Sweden, Finland and Kola Peninsula). This population decreased drastically around the turn of the century as a result of extreme fur prices which caused severe hunting also during population lows (Lönnberg 1927, Zetterberg 1927). The population has remained at a low density for more than 90 years, with additional reductions during the last decade (Angerbjörn et al. 1995). The total population estimate for 1997 is c. 60 adults in Sweden, 11 adults in Finland and 50 in Norway. From Kola, there are indications of a similar situation, suggesting a population of c. 20 adults. The Fennoscandian population thus numbers a total of 140 breeding adults. Even after local lemming peaks, the arctic fox population tends to collapse back to levels dangerously close to non-viability (Tannerfeldt 1997).



The arctic fox remains the single most important terrestrial game species in the Arctic. Indigenous peoples have always utilised its exceptional fur, and with the advent of the fur industry, the arctic fox quickly became an important source of income. Today, leg-hold traps and shooting are the main hunting methods. Because of their large reproductive capacity, arctic foxes can maintain population levels also under high hunting pressure. Up to 50% of the total population has in some areas been harvested on a sustainable basis (Nasimo-vich and Isakov 1985). However, this does not allow for hunting during population lows, as shown by the situation in Fennoscandia (see previous section). The arctic fox has nevertheless survived high fur prices better than most other Arctic mammals. Hunting has declined considerably in the last decades, as a result of low fur prices and alternative sources of income. In the Yukon, for example, the total value of all fur production decreased from 1.3 million $ in 1988 to less than 300 000 $ in 1994.

Around the turn of the century, the fur industry in Russia and America introduced arctic foxes also to previously isolated islands, where they have caused severe declines or exterminations of many local bird populations. Efforts have been made in the Aleutian chain to eradicate arctic foxes from such islands, by hunting, by poisoning and by the introduction of sterile red foxes (Schmidt 1985, Bailey 1992).

North America
The yearly harvest for North America in 1919–1984 was on average 40 000, with around 85 000 during peaks (Garrott and Eberhardt 1987). The fur trading Hudson Bay Company in Canada registered around 2 000–12 000 and up to 25 000 arctic fox pelts per year during 1850–1915 (Elton 1924). Macpherson (1969) later stated that the Canadian production was to 10 000–68 000 pelts per year. The yield from Alaska was around 3 900 pelts per year 1925–1962, with a peak of 17 000 in 1925 (Chesemore 1972).

In a most comprehensive summary of Siberian arctic fox data, Nasimovich and Isakov (1985) reported the number of live animals on the Taymyr Peninsula alone to be 52 000 during a low and up to 433 000 animals in a peak year (1970/71). The total fur returns from Siberia reached more than 100 000 animals in some years. These populations fluctu-ate widely and a large proportion of killed animals are young-of-the-year. A decline during the last decades can be discerned in many Siberian areas (Nasimovich and Isakov 1985), but lower fur prices and a breakdown of the Soviet trading system has probably relieved the pressure on the species.

On Iceland, the arctic fox population is estimated to some 2000 animals, although the species was subject to an eradication campaign for more than 700 years, as it is considered a pest to sheep farmers and eider down collectors (Hersteins-son et al. 1989). The bounty campaign was recently stopped but hunting is still allowed in non-protected areas.

In Greenland, the arctic fox mainly occurs on the western coast. In the year 1800, the number of exported pelts per year was around 2000. One hundred years later it was 5600, and by 1939 the catch had increased to over 7000 animals per year (Bræstrup 1941). Today, arctic fox hunting has decreased also in Greenland.



In most of its range, the arctic fox is neither protected, nor endangered. In 1983 the Mednyi Island foxes were listed in the Russian Red Data Book. The island is protected as a Nature Reserve since 1993. In Fennoscandia except the Kola Peninsula, the species and its dens have total legal protection since 1928 (1940 in Finland). An action plan has been developed for Sweden (SNV 1998) and a status report is under way in Norway.



The main threat to the Mednyi island population is the mange infection (see under Status). In Fennoscandia, the main threat is the small population size, at present constrained by low food availability (Tannerfeldt 1997). Summer food, and thereby juvenile recruitment, is currently limited by an absence of lemming and vole peaks (Tannerfeldt et al. 1994). The reasons for this absence remain unclear, but the effects are severe as the situation has persisted for 20 years. The arctic fox is also dependent on larger predators leaving remains of carrion. The present low number of these predators in Fennoscandia cause a winter food scarcity for arctic fox. The red fox is a dominant competitor and particularly a severe predator on juvenile arctic foxes (Frafjord et al. 1989). It is currently increasing its range above the tree line, taking over dens and thus restricting the range for arctic fox (Hersteinsson and Macdonald 1982). Both the absence of rodent peaks and the increase in range of the red fox may be influenced by anthropogenic changes, but the causal relations are little known. Dependence on specific den sites for breeding also make the foxes vulnerable to certain types of disturbance, such as hunting with dogs in late summer in sensitive areas.


Critical issues

* Diseases introduced by humans
* An absence of rodent peaks in Fennoscandia
* Low numbers of large predators leaving carcasses
* The red foxes spreading northwards


Literature cited

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