Northern Swift Fox

Vulpes velox hebes

Description

The northern swift fox, the smallest of the foxes, has a slender body that ranges from 16-32 in (40-80 cm) in length. Coloration is gray to yellowish brown with white underparts. The snout is marked by a dark spot on either side. The ears are long and pointed.

The validity of the subspecies designation for the northern swift fox has been questioned. Some mammalogists believe that the historic division of the swift fox into a southern race (Vulpes velox velox ) and a northern race (V. v. hebes ) is an error. In 1986 a taxonomic study concluded that the northern swift fox was not a valid subspecies. However, it went on to note that the swift fox showed significant geographic variation and suggested that there may be genetic uniqueness in some geographic populations.

Behavior

The swift fox is nocturnal in summer and spends the day in underground burrows; in winter it may become more diurnal. It feeds mostly on small mammals, particularly mice and voles, seasonally supplementing its diet with insects and plant matter. It is very vocal, yapping excitedly when fighting and yowling long and loudly during the midwinter rutting season. After a gestation period of about 52 days, a litter of three to five pups is born. Pups nurse for three or four weeks. After weaning, the female first regurgitates food for her young, then brings solid food to the den, and finally supplies pups with live prey.

Habitat

The northern swift fox can use a great variety of habitat types, especially grasslands, plains, and foothills. It prefers to dig its den in woods and sometimes enlarges abandoned badger or rabbit dens. When it excavates its own den, the entrances are designed to be too small for badgers, coyotes, or foxes. This swift fox occupies a large number of shallow temporary dens while creating larger, more complex dens within its home range. Dens abandoned by the northern kit fox are often inhabited by striped skunks, burrowing owls, deer mice, and a variety of invertebrates, making the fox's presence important to the animal ecosystem.

Distribution

The swift fox (V. v. velox ) ranges from the Staked Plains of northwestern Texas northward over the Great Plains to South Dakota. The northern race (V. v. hebes ) was once common from North Dakota and Montana to the Saskatchewan River in Saskatchewan and Manitoba, Canada. The last native swift fox was sighted in Canada in 1938.

Swift foxes, presumably of the northern race, survive in very low numbers in the northern plains of the United States—Montana, North Dakota, and portions of South Dakota. Since 1983, captive-bred swift foxes have been released yearly in Canada by the Canadian Wildlife Service. These foxes are descended from wild foxes captured in Colorado, Wyoming, and South Dakota, within the range of the southern race (V. v. velox ).

Threats

The main reason for the decline of the northern swift fox was the loss of habitat due to increasing settlement, agriculture, recreation, and other human activities. As prairie was converted for agricultural use, the fox's natural prey diminished. Poisons and traps set for coyotes and wolves often killed swift foxes.

Conservation and Recovery

In 1978 the Canadian Committee on the Status of Endangered Wildlife declared that wild swift foxes no longer survived in Canada. In 1983 the Canadian Wildlife Service began releasing captive-bred foxes derived from southern race breeding stock. So far about 250 foxes have been released at various sites in southeastern Alberta and southwestern Saskatchewan. As of January 1989, it is believed that about 50 swift foxes survived in the Canadian wild.

This leaves the northern swift fox, if it exists as a valid subspecies, in an unusual position for an Endangered species. The only remaining northern swift foxes exist in the United States where they are not currently protected under the Endangered Species Act. Instead, the law protects the subspecies in Canada, where it no longer occurs. The more common southern race (V. v. velox ) is currently under study by the U. S. Fish and Wildlife Service to determine whether it should be federally listed as Threatened or Endangered.

Contacts

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
P.O. Box 25486
Denver Federal Center
Denver, Colorado 80225
http://www.r6.fws.gov/

Canadian Wildlife Service
351 St. Joseph Boulevard
Ottawa, Ontario K1A0H3

References

Carbyn, L. N. 1989. "Swift Foxes in Canada." Recovery (An Endangered Species Newsletter) Canadian Wildlife Service 1:8-9.

Herrero, S., C. Schroeder, and M. Scott-Brown. 1986."Are Canadian Foxes Swift Enough?" Biological Conservation 36:159-167.

Stromberg, M. R., and M. S. Boyce. 1986. "Systematics and Conservation of the Swift fox, Vulpes velox in North America." Biological Conservation 35:97-110.