Mustela nigripes (Audubon and Bachman)
Black-footed ferret (Mustela nigripes), Mosher, South Dakota, 15 August 1964.
Photo courtesy of Robert Powell.
Description: The black-footed ferret can be distinguished by: 1) long body, somewhat bulkier than other members of the genus, 2) short black legs and feet, the front feet with well-developed claws, 3) tail approximately one third of its body length, the terminal quarter black, 4) relatively conspicuous ears, 5) short, soft dorsal fur, pale ochre to buffy in color, fading to white on the sides and ventral surfaces, with a brown middorsal stripe running from the back of the head to the base of the tail, 6) white muzzle, forehead, and ears, with a black band between and around the eyes, and 7) often having a thin black midventral stripe on the lower abdomen (especially in males). Males grow slightly larger than females.
Size: Adults may attain the following dimensions: total length 457-572 mm; tail 90-150 mm; hind foot 57-68 mm; ear 27-32 mm; eight 530-590 grams.
Range and Habitat: The black-footed ferret once ranged over the western two-thirds of the state where its distribution and habitat were essentially the same as the black-tailed prairie dog. It inhabited short grass prairie in well-drained soils. It may now be extinct in Kansas.
Reproduction: Almost nothing is known of the breeding habits of black-footed ferrets. It is thought that breeding occurs in April or May and that gestation is probably 37 to 42 days in length. Litters range in size from two to five young which are born in a burrow. The young are born naked and blind. The female provides all care for the offspring. The young begin to appear above ground when they are about half grown. Through June and July, the young accompany the female while she hunts, and eat prey captured by the female. By August the young occupy separate burrows within the female's home range, and begin to hunt for themselves. The young begin to appear above ground when they are about half grown. Through June and July, the young accompany the female while she hunts, and eat prey captured by the female. By August the young occupy separate burrows within the female's home range, and begin to hunt for themselves. The young disperse from August to October, finding their own burrows in other Prairie dog colonies. Nothing has been reported for this species on the age at which reproductive maturity is attained.
Habits: Black-footed ferrets are primarily crepuscular and nocturnal in their daily activities. They occasionally are active during daylight, especially from late autumn through spring. During summer most of their daytime activity consists of sunning themselves near their burrows. The home range size of black-footed ferrets is unknown, but they may occupy prairie dog colonies that are at least 4.5 hectares in size. Population densities have, apparently, always been very low. Black-footed ferrets appear to be solitary. Usually only single individuals or a female and her litter live in a prairie dog colony.
Black-footed ferrets usually den in prairie dog burrows. Less frequently they build their own dens or modify ground squirrel burrows. They are excellent burrowers and may tunnel four to five meters in a single night. Characteristically, burrowing involves the dirt being pulled out of the tunnel with the front feet, then kicked back with the rear feet. This creates a fan-shaped pile of dirt one half to 3 meters long with a trench-like depression in the middle. Black-footed ferrets seem to prefer to occupy old prairie dog burrows with two or more openings.
Food: The black-footed ferret's diet consists primarily (up to 95 percent) of prairie dogs. They are also reported to feed on voles, deer mice, ground squirrels, rabbits, snakes, ground nesting birds and insects.
Remarks: The black-footed ferret is an endangered species, and is protected by federal law. The last verified sighting in Kansas was in December 1957 near Studley in Sheridan County. The decline of black-footed ferret populations appears to be directly related to control measures taken by humans against prairie dogs. Several factors appear involved. The relatively large prairie dog colonies necessary to support a single black-footed ferret have been reduced in numbers in Kansas. Their solitary behavior requires several prairie dog colonies in close proximity for black-footed ferrets to be able to breed. Finally, black-footed ferrets will eat poisoned prairie dogs, and are susceptible to the poisons used for prairie dog control. Long-tailed weasels in southwestern Kansas are frequently mistaken for black-footed ferrets. however, they are quite different in appearance, and do not construct the trench-like diggings characteristic of ferrets. Feral domestic ferrets are sometimes encountered, and have been confused with native ferrets. Badgers, coyotes, bobcats, hawks, and owls are considered possible predators of black-footed ferrets. Nothing has been reported on the longevity of the black-footed ferret.
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