Swift Fox

The swift fox (Vulpes velox) and its close relative, the kit fox (V. macrotis), represent the smallest North American members of the family Canidae – a family that also includes the coyote and the wolf. Weighing from 4 to 6 pounds and measuring just over 2 feet long, the swift fox is a uniform buffy tan except for a black-tipped tail and dark patches on either side of its nose.

The swift fox is an opportunistic predator of small mammals, birds, and insects, and will also feed on some agricultural crops such as sunflower seeds. Swift and kit foxes are the most den dependent members of the North American canids. Dens are used on a daily basis year long. Swift foxes can construct their own dens, or may make use of burrows dug by prairie dogs (Cynomys ludovicianus) or badgers (Taxidea taxus). Burrows provide swift foxes protection from other predators and shelter from the prairie environment, primarily during the day, as they are one of the most nocturnal of the North American canids.

The swift fox is believed to have originally been abundant throughout its range on the Great Plains. The swift fox originally lived throughout the Great Plains from the southern portion of the Canadian prairie provinces south to central Texas, and as far east as western Iowa and Minnesota. The Rocky Mountains represent the western margin of its range.

The swift fox, however, was extirpated early in this century from the northern portion of its range while remnant populations in the southern portion survived human settlement of the prairies. The original cause of this widespread extirpation is attributed to the tendency of the swift fox to get into poisoned baits and traps placed for coyote (Canis latrans) and wolf (Canis lupus) extermination. Loss of habitat to dry land agriculture, prairie dog and ground squirrel control, and increased interspecific competition from coyotes and red foxes (V. vulpes) may have also contributed to this decline.

Swift foxes use, and prefer, short to mid-grass prairies. Within these habitats they prefer areas of short vegetation and nearly level topography. Prairie habitats dominated by buffalo grass (Buchloe dactyloides) or blue grama grass (Bouteloua gracilis) appear to be the areas where the highest densities of swift foxes are found. Although swift foxes may be found in agricultural areas, recent studies show that their preference is for native grassland habitats.

Timing of breeding in the swift fox varies across its range. The swift fox breeds in December and early January in Oklahoma, January and February in Colorado, and in February and early March in Nebraska. The swift fox is believed to be monogamous, although two males or females may occasionally be present at a den site during the breeding season. These helpers at the den are thought to be young from a previous litter. The swift fox has a gestation period of 52-53 days. Young are born in March and early April in the south, and April and early May in the north.

Generally, a litter consists of 3 or 4 pups, whose eyes and ears open at about 10 - 15 days. Young emerge from dens at three to four weeks of age and are weaned at 6 - 7 weeks. Pups weigh less than a 1/4 kg at birth but grow rapidly and obtain adult weight by early fall. Dispersal of pups does not occur until late summer or early fall. Swift and kit fox pups stay with family groups and use their natal dens longer than most other North American canids.

Swift fox populations have a high annual mortality rate, with coyotes acting as a significant cause of natural mortality across the swift fox’s range. Some have speculated that with the disappearance of the gray wolf, coyotes increased in abundance and have reduced swift fox populations. Human related activity appears to be another common cause of mortality, as swift fox are often struck by vehicles, shot, and trapped. Many authors have noted the dependency of swift foxes on dens and interpreted this as an indication that swift fox are very vulnerable to predation. Golden eagles (Aquila chrysaetos) and other raptors have been found to feed on swift fox but in many cases it is not known if they had killed the animals or if they were scavenging.

Learn More

Seven Million Americans Tell Forest Service: Time to Revise Grassland Management [PCA Press Release, January 24, 2002]

Restoring the Prairie Dog Ecosystem of the Great Plains [PCA Report, 2001]