The Arctic Fox Alopex
By PhD Magnus
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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 foxs
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 4250 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 parents 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
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°40N
(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
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
1970s (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
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).
The yearly harvest for North America in 19191984 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 00012 000 and up to 25 000 arctic fox pelts per year during
18501915 (Elton 1924). Macpherson (1969) later stated that the
Canadian production was to 10 00068 000 pelts per year. The
yield from Alaska was around 3 900 pelts per year 19251962,
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
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
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
* Diseases introduced
* An absence of rodent peaks in Fennoscandia
* Low numbers of large predators leaving carcasses
* The red foxes spreading northwards
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