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  The Mammals of Texas - Online Edition

Black-footed Ferret
Order Carnivora : Family Mustelidae : Mustela nigripes (Audubon and Bachman)

Black-footed Ferret (Mustela nigripes).  Photo courtesy of U.S. Fish and Wildlife Service.Description. A large edition of the common long-tailed weasel; upperparts pale buffy yellow, overcast with brown hairs on head and back; underparts buffy or cream-colored; feet and tip of tail blackish; broad, black mask across face and eyes. External measurements average: (males), total length, 570 mm; tail, 133 mm; hind foot, 60 mm; (females), 500-120-55 mm. Weight, probably 850-1,400 g in males, 450-850 g in females.

Distribution in Texas. Originally the same as that of the black-tailed prairie dog, roughly the northwestern third of Texas including the Panhandle, much of the Trans-Pecos, and a considerable part of the Rolling Plains east and southeast of these areas. Now extirpated from Texas. The last Texas records were from Dallam County (1953) and Bailey County (1963).

Habits. Black-footed ferrets are associated primarily with prairie dogs and prairie dog towns. Although individuals have been seen under haystacks, in alfalfa fields, and in buildings, most of these sightings were made during the fall dispersal of the young. Historically, the range of the ferret has coincided closely with that of the various species of prairie dogs which are the main source of the ferret’s food. In addition, prairie dog burrows provide the ferrets with shelter and nursery sites for rearing their young.

Both the young and the adults are primarily nocturnal. Young ferrets rarely appear above ground during daylight hours until about mid-August. Adults, however, occasionally leave their burrows during the day to sunbathe or to forage. When a ferret is active in daylight, the prairie dogs stay above ground, keep the intruder under surveillance, and appear to be highly nervous and agitated. This behavior of the prairie dogs is one of the clues one can rely on that a ferret is present in the dog town. A better clue, however, is the presence of a peculiar, shallow trench leading from a prairie dog burrow. When a ferret alters a prairie dog burrow or digs one of its own, it backs out with the dirt held against its chest and drags the dirt farther from the burrow entrance each time. The result is a trench 8-12 cm wide and up to 3.5 m long. These trenches are formed mostly at night and, if fresh, are a sure sign of the presence of a ferret. No other species of animal living in a dog town leaves this type of structure.

As mentioned above, the mainstay of black-footed ferrets is prairie dogs which the ferrets capture and kill in their burrows at night. Analyses of 56 scats revealed that remains of prairie dogs occurred in 51 of them and comprised 82% of the identifiable animal material. Mouse remains occurred in 19 scats and made up the remaining 18%. Ferrets have also been seen chasing birds and catching moths. Determining their food habits by scat analyses can become quite a chore because the ferrets deposit most of their feces in the burrows they occupy. Only a few scats have ever been found aboveground by investigators diligently searching for them.

Mating is believed to occur in April or May. One female killed on May 16 appeared to be in heat; a female trapped May 3 was pregnant; a nursing female was captured on June 20. The female alone cares for her litter of four or five young even though the male may stay in the same dog town. As soon as the young are able to travel the female coaxes them out of the nest burrow and leads them as she carefully checks several other burrows and finally selects one for her litter and a separate one for herself. As they grow older, the young readily follow their mother and from June to mid-July they may be seen regularly at night as the family extends its activities. By mid-July the young are half-grown and readily eat prey which the female kills. By early August the young ferrets are usually occupying separate burrows in the dog town and by mid-August they are often out during the early morning, playing, and following their mother. By early September the young are nearly full-grown and begin to disperse from their birth place. It is during the period of dispersal that the young are exposed to the greatest danger. More than 40% of the dead ferrets found outside prairie dog towns were recorded from mid-August to mid-October. Ferrets do not hibernate and during late fall, winter, and spring they are usually found singly.

Remarks. The black-footed ferret is an endangered species and is now offered full protection by Federal regulations and cannot be killed or captured legally without a special permit. Although all of the western states have conducted intensive surveys in recent years for black-footed ferrets, only one colony at Meteetsee, Wyoming, was found. These ferrets, numbering about 130 in 1984, subsequently suffered an epidemic of canine distemper that left the species on the brink of extinction. Beginning in 1986, the remaining 18 ferrets known to have survived at the Meteetsee site were captured and put into a captive breeding program with the hope that successful matings would one day allow for the return of this species to its natural habitat. By late 1992, the captive breeding population totaled 225. In the fall of 1991, 49 ferrets were released in the Shirley Basin area of Wyoming. By the spring of 1992, four of these original 49 remained, and two litters of two and four young had been born in the wild. An additional 83 captive-born ferrets were released in Shirley Basin during the fall of 1992.

Photo courtesy of U.S. Fish and Wildlife Service.