Arctic fox
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| Alopex lagopus (Linnaeus, 1758) |
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 Arctic Fox range
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Vulpes lagopus |
Arctic fox, also known as the polar fox, is a small fox native to cold Arctic regions of the Northern Hemisphere. It is common in all three tundra biomes. Although some authorities have suggested placing it in the genus Vulpes, it has long been considered the sole member of the genus Alopex. The Arctic fox has smaller, more rounded ears, a more rounded braincase, and a slightly shorter and broader muzzle than the red fox, Vulpes vulpes (Clutton-Brock et al. 1976). Its feet are furrier than those of other foxes. The Arctic fox occurs in two distinct colour morphs, "blue" and "white". Each colour phase also changes seasonally: "blue" moults from chocolate brown in summer to lighter brown tinged with a blue sheen in winter, and "white" is almost pure white in winter, and in summer grey to brownish-grey dorsally, and light grey to white below. Colour morphs are determined genetically at a single locus, white being recessive. The "blue" morph comprises less than 1% of the population through most of its continental range, but this proportion increases westwards in Alaska, and on islands. In Greenland roughly half of Arctic foxes are of the blue morph, and in Iceland most of them are blue.
The Arctic fox has evolved to live in the most frigid extremes on the planet. Among its adaptations for cold survival are its deep, thick fur, a system of countercurrent heat exchange in the circulation of paws to keep them from freezing, and a good supply of body fat. The fox has a low surface-area-to-volume ratio as evidenced by its generally rounded body shape, short muzzle and legs, and short, thick ears. Since less of its surface area is exposed to the cold, less heat escapes the body. Its furry paws allow it to walk on ice flows in search of food. It is also able to walk on top of snow and listen for the movements of prey underneath. It has the warmest fur of any mammal.
Arctic foxes mate in early March to early April. The gestation period is 52 days. Litters tend to average seven pups but may be as many as fifteen. Both the mother and the father help to raise their young. The males leave the family and form their own groups and the females stay with the family.
Arctic foxes will eat pretty much anything. Their prey includes voles, lemmings, hares, ground squirrels, and bird eggs. Foxes living on the coast also eat shellfish, sea urchins, dead seals and fish, beached whales, and nesting seabirds. In winter when food is scarce, they may follow a polar bear and after the bear makes a kill, eats and leaves, they will steal what ever scraps of meat are left. In winter, their light coat protects them from predators, esp. polar bears, by blending in to the white snow.
Head-and-body length: 55 cm (21.7 in) (male); 53 cm (21 in) (female).
Tail length: 31 cm (12.2 in) (male); 30 cm (11.8 in) (female)
Shoulder height: 25-30 cm (9.9-11.8 in).
Weight: 3.8 kg (8.2 lb) (male); 3.1 kg (6.7 lb) (female).
[edit] Subspecies
- Alopex lagopus beringensis
- Alopex lagopus fuliginosus
- Alopex lagopus groenlandicus
- Alopex lagopus hallensis
- Alopex lagopus innuitus
- Alopex lagopus sibiricus
- Alopex lagopus spitzbergensis
- Alopex lagopus ungava
The Arctic fox will generally eat any meat it can find, including lemmings, Arctic hares, birds and their eggs, and carrion. Lemmings are the most common prey. A family of foxes can eat dozens of lemmings each day. During April and May the Arctic fox also preys on ringed seal kits when the young animals are confined to a snow den and are relatively helpless. When its normal prey is scarce, the Arctic fox scavenges the leftovers of larger predators, such as polar bears, even though the bears' prey includes the Arctic fox itself.
Foxes tend to form monogamous pairs in the breeding season. Litters of between six and eighteen kits are born in the early summer, a very large litter size for a mammal. The parents raise the young in a large den. Dens can be complex underground networks, housing many generations of foxes. Young from a previous year's litter may stay with the parents to help rear younger siblings.
The habitat of the Arctic fox spans coastal to inland tundra areas. The white morph is generally associated with true tundra habitat, the blue more with coastal habitat.
[edit] Population and distribution
The Arctic fox has a circumpolar range, meaning that it is found throughout the entire Arctic, including the outer edges of Greenland, Russia, Canada, Alaska, and Svalbard, as well as in sub-Arctic and alpine areas, such as Iceland and mainland alpine Scandinavia. The conservation status of the species is good, except for the Scandinavian mainland population. It is acutely endangered there, despite decades of legal protection from hunting and persecution. The total population estimate in all of Norway, Sweden and Finland is a mere 120 adult individuals.
The abundance of the Arctic fox species tends to fluctuate in a cycle along with the population of lemmings. Because the fox reproduces very quickly and often dies young, population levels are not seriously impacted by trapping. It has, nonetheless, been eradicated from many areas where humans are settled.
The Arctic fox is losing ground to the larger red fox. Historically, the gray wolf has kept red fox numbers down, but as the wolf has been hunted to near extinction in much of its former range, the red fox population has grown larger, and it has taken over the niche of top predator. In areas of northern Europe there are programs in place that allow hunting of the red fox in the Arctic fox's previous range.
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).
[edit] References
- Nowak, Ronald M. (2005). Walker's Carnivores of the World. Baltimore: Johns Hopkins Press. ISBN 0-8018-8032-7
- Angerbjörn et al (2004). Alopex lagopus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes justification for why this species is of least concern
