Swift Fox
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Once common throughout the short and mixed-grass prairie regions, North America's smallest canid, the Swift Fox
(Vulpes velox), suffered dramatic range-wide declines in the late 1800s and early 1900s. In Canada, the
species disappeared from historic range in the early twentieth century and has been listed as
extirpated since 1978. Although severe declines have also occurred in the United States, the Swift Fox is not listed as
endangered at the federal level in that country. Reintroduction efforts in the Canadian prairies over the past 14 years have resulted in the establishment of small populations in southern Alberta and Saskatchewan. Currently the Swift Fox is designated as
endangered under the Alberta Wildlife Act.
Swift Foxes typically prefer short or mixedgrass prairie with flat to gently rolling terrain and sparse vegetation which allow for good mobility and visibility. Native grasses and bushes such as blue
grama, spear grass, fescue and pasture sage are the dominant vegetation in these areas. In Wyoming, prairie/sagebrush
habitat is also highly utilized by the Swift Fox.
Coulees, brushy areas and cultivated lands are usually avoided, although Swift Foxes have been observed near settlements and agricultural lands.
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In addition to unfragmented prairie, several other habitat features are necessary to support Swift Fox populations. Unlike other canids, Swift Foxes use multiple den sites year round for shelter and rearing young, and as escape routes from predators. The presence of fossorial animals, such as Badgers and Richardson's Ground Squirrels, is crucial as Swift Foxes will modify existing burrows. New dens may also be excavated. Den location is variable, perhaps dependent on local topography. Dens have been located on hill tops in well-drained sites, as well as in predominantly flat terrain. Permanent water bodies and low predator abundance also enhance habitat suitability for Swift Fox.
Within Canada, extensive fragmentation of native prairie has resulted in a limited number of sites with the landscape attributes necessary to support substantial Swift Fox populations. Most areas of suitable habitat, which remain are located in southern Alberta and Saskatchewan and are privately owned, leased lands or community pastures.
Primarily nocturnal, Swift Foxes are opportunistic predators that consume a variety of prey including mammals,
grasshoppers and beetles, vegetation and small birds. Fish, amphibians and reptiles
may also be included in the Swift Fox diet.
Swift Foxes appear to be monogamous however examples of possible polygamy or presence of a "helper" individual have been recorded. Breeding usually begins in the second year, although yearling females have been documented with pups. The breeding season starts in mid-February, and foxes reintroduced to Alberta and Saskatchewan have produced pups from late April to early May.
Litter size of reintroduced animals has ranged from one to seven pups, with an average litter size of 3.9.
Juveniles typically disperse in the late summer and autumn, when they are four or five months
old. Swift Foxes do not appear to be territorial and home ranges may overlap in high-quality habitat.
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Predation was the principal cause of mortality and accounted for 58% of known deaths
of 89 of the Swift Foxes released between 1987 and 1991 on the Canadian prairies. Coyotes are the main predators and will often kill, but not consume the much smaller Swift Fox in what appears to be interspecific competition between the two species. Other predators include the Badger, Golden Eagle and Bobcat. Human induced mortality, due to road kills, hunting or trapping, also occur to a lesser extent.
Despite the high rate of annual mortality, it is estimated that an average litter size of 3.9 was sufficient to support slow growth of the Canadian Swift Fox population.