The black-footed ferret (Mustela nigripes), also called the American polecat or prairie dog hunter, is a type of animal in the weasel family that lives in central North America.
This animal is about the same size as a mink and looks similar to the European polecat and the Asian steppe polecat. It is mostly active at night and spends most of its time alone, except when it is mating or caring for its young. More than 90% of its food comes from prairie dogs.
The black-footed ferret’s numbers dropped during the 20th century mainly because prairie dog populations decreased and a disease called sylvatic plague spread. It was declared extinct in 1979, but a small group of wild ferrets was found in Meeteetse, Wyoming, in 1981. A program that bred ferrets in captivity, started by the United States Fish and Wildlife Service, helped reintroduce them to eight western U.S. states, Canada, and Mexico between 1991 and 2009. By 2015, more than 200 adult ferrets lived in the wild across 18 groups, with four groups in South Dakota, Arizona, and Wyoming that can survive on their own. The species was first listed as "endangered" in 1982, then as "extinct in the wild" in 1996, and later moved back to "endangered" on the IUCN Red List in 2008. In February 2021, the first cloned black-footed ferret, a female named Elizabeth Ann, was introduced to the public.
Evolution
The black-footed ferret is more advanced in its diet that includes a lot of meat compared to the European polecat, similar to its close relative, the Asian steppe polecat. Scientists once thought the black-footed ferret and the Asian steppe polecat were the same species. Both the black-footed ferret and the European polecat likely descended from an ancestor called Mustela stromeri, which lived in Europe during the Middle Pleistocene. Scientific studies using DNA suggest the steppe polecat and black-footed ferret separated from M. stromeri between 500,000 and 2,000,000 years ago, possibly in a region called Beringia. The black-footed ferret appeared in the Great Basin and the Rocky Mountains by 750,000 years ago. The oldest known fossil of this species was found in Cathedral Cave, White Pine County, Nevada, and is about 750,000 to 950,000 years old. Prairie dog fossils have been found at six sites where ferrets were also discovered, showing the two species have shared a long connection. Observations and 42% of fossil records suggest that colonies of medium- to large-sized ground squirrels, like Richardson's ground squirrels, could provide enough food and shelter for black-footed ferrets. This means the black-footed ferret and prairie dogs did not depend completely on each other as predator and prey. The black-footed ferret has likely always been a rare species, and today’s population is likely a remnant of an earlier group. Fossils of this species have been found in a late Illinoian deposit in Clay County, Nebraska, and in Sangamonian deposits in Nebraska and Medicine Hat, Alberta. Additional fossils from the Pleistocene have also been discovered in Alaska.
Description
The black-footed ferret has a long, thin body with black outlines on its paws, ears, parts of its face, and tail. Its forehead is curved and wide, and its muzzle is short. It has few whiskers, and its ears are triangular, short, upright, and wide at the base. The neck is long, and the legs are short and thick. The toes have sharp, slightly curved claws. Both the top and bottom of the feet are covered in hair, even on the soles, which hides the claws. The black-footed ferret shares physical traits found in both members of the subgenus Gale (least and short-tailed weasels) and Putorius (European and steppe polecats). Its skull is similar to polecats in size, shape, and the development of ridges and depressions. However, it is different because the area behind the eye sockets is extremely narrow, making the skull much narrower than the muzzle.
Although similar in size to polecats, the black-footed ferret has a thin body, long neck, very short legs, slim tail, large round ears, and closely packed fur, which makes it more similar to weasels and stoats. Its teeth are similar to those of the European and steppe polecat, but the back lower molar is underdeveloped, with a small, round crown that lacks the small bumps seen in polecats. It differs from the European polecat by having a stronger contrast between its dark limbs and light body and a shorter black tail tip. Differences from the steppe polecat of Asia are small, leading scientists to once think they were the same species. The only clear differences between the black-footed ferret and the steppe polecat are the ferret’s shorter, coarser fur, larger ears, and longer part of the palate behind the molars.
Male black-footed ferrets measure 500–533 millimeters (19.7–21.0 inches) in body length and 114–127 millimeters (4.5–5.0 inches) in tail length, meaning the tail makes up 22–25% of their body length. Females are usually 10% smaller than males. They weigh 650–1,400 grams (1.43–3.09 pounds). Ferrets bred in captivity for reintroduction programs were smaller than wild ferrets but quickly reached historical sizes after being released.
The base color of the black-footed ferret is pale yellowish or buffy on the top and bottom of the body. The top of the head and sometimes the neck have dark-tipped hairs. A wide band of sooty black crosses the face, including the eyes. The feet, lower legs, tail tip, and area near the genitals are sooty-black. A large patch of dark umber-brown appears between the front and back legs, fading into the buffy surrounding areas. A small spot is present over each eye, with a narrow band behind the black mask. The sides of the head and ears are dirty-white in color.
Behavior and ecology
The black-footed ferret is usually alone, except when it is mating or caring for its young. It is active at night and mainly hunts sleeping prairie dogs in their burrows. It is most active above ground from dusk to midnight and from 4 a.m. to mid-morning. Activity above ground is highest in late summer and early autumn when young ferrets become independent. Temperature generally does not limit the ferret’s activity, but it may stay inactive inside burrows for up to 6 days during winter.
Female black-footed ferrets have smaller home ranges than males. A male’s home range may sometimes include the home ranges of several females. Adult females usually stay in the same area every year. A female that was tracked from December to March lived in an area of 39.5 acres (16 hectares). A male that lived in the same area during that time had a home range of 337.5 acres (137 hectares). The average number of black-footed ferrets near Meeteetse, Wyoming, is about one ferret for every 148 acres (60 hectares). In 1985, 40 to 60 black-footed ferrets lived in a total of 6,178 to 7,413 acres (2,500 to 3,000 hectares) of white-tailed prairie dog habitat. From 1982 to 1984, the average distance that 15 black-footed ferrets moved each night between prairie dog colonies was 1.6 miles (2.5 kilometers) (with a range of 1.1 miles or 1.7 kilometers). Movement between prairie dog colonies is influenced by factors such as breeding, season, sex, competition between ferrets, prey density, and the size of home ranges as population density decreases. Ferrets move more during the breeding season, but snow-tracking from December to March over 4 years near Meeteetse, Wyoming, showed that other factors, not just breeding, caused movement.
The distance black-footed ferrets move is related to temperature. Snow-tracking from December to March over 4 years near Meeteetse showed that movement was shortest in winter and longest between February and April, when ferrets were breeding and prairie dogs left hibernation. The average nightly movement of 170 black-footed ferrets was 0.87 miles (1.4 kilometers) (ranging from 0.001 to 6.91 miles (0.0016 to 11.12 kilometers)). The area where ferrets were active ranged from 1 to 337.5 acres (0 to 137 hectares), with larger areas in February to March (110.2 acres (45 hectares)) than in December to January (33.6 acres (14 hectares)). Adult females choose activity areas based on food availability for their young. Males choose larger areas to find females.
The number of prey may affect how far ferrets travel. Black-footed ferrets may move up to 11 miles (18 kilometers) to find prey, showing they move freely between prairie dog colonies less than 11 miles (18 kilometers) apart. In areas with many prey, ferrets move in complex patterns, likely to avoid predators. From December to March over 4 years, ferrets investigated 68 prairie dog burrows per mile (1.6 kilometers)
Diet
The black-footed ferret's diet is mostly made up of prairie dogs. About 10% of their food comes from small rodents and lagomorphs. Their food choices change depending on where they live. In western Colorado, Utah, Wyoming, and Montana, black-footed ferrets are historically linked to white-tailed prairie dogs. When these prairie dogs hibernate for four months, the ferrets must find other prey. In Wyoming, during hibernation, ferrets ate voles and mice near streams. In South Dakota, black-footed ferrets are associated with black-tailed prairie dogs. Since black-tailed prairie dogs do not hibernate, the ferrets' diet does not change much with the seasons.
In Mellette County, South Dakota, black-tailed prairie dog remains were found in 91% of 82 black-footed ferret scats. Mouse remains were found in 26% of scats. Mouse species could not be identified, but deer mice, northern grasshopper mice, and house mice were captured in trap surveys. Other possible prey included thirteen-lined ground squirrels, plains pocket gophers, mountain cottontails, upland sandpipers, horned larks, and western meadowlarks.
In Meeteetse, Wyoming, 87% of the food in 86 black-footed ferret scats was white-tailed prairie dogs. Other food items included deer mice, sagebrush voles, meadow voles, mountain cottontails, and white-tailed jackrabbits. Water is obtained by eating prey.
A study published in 1983 estimated the energy needs of one adult female black-footed ferret and her litter. It found that they would need about 474 to 1,421 black-tailed prairie dogs or 412 to 1,236 white-tailed prairie dogs each year to survive. This would require protecting 91 to 235 acres (37 to 95 hectares) of black-tailed prairie dog habitat or 413 to 877 acres (167 to 355 hectares) of white-tailed prairie dog habitat for each female with a litter.
Distribution and habitat
The area where black-footed ferrets lived was closely connected to, but not limited to, the area where prairie dogs (Cynomys spp.) lived. Their range stretched from southern Alberta and southern Saskatchewan south to Texas, New Mexico, and Arizona. By 2007, the only known wild black-footed ferret population was found on about 6,000 acres (2,400 hectares) in the western Big Horn Basin near Meeteetse, Wyoming. Since 1990, black-footed ferrets have been reintroduced to the following areas: Shirley Basin, Wyoming; UL Bend National Wildlife Refuge and Fort Belknap Indian Reservation, Montana; Conata Basin/Badlands, Buffalo Gap National Grassland, Wind Cave National Park, and the Cheyenne River Sioux Reservation in South Dakota; Aubrey Valley, Arizona; Rocky Mountain Arsenal National Wildlife Refuge and Wolf Creek, Colorado; Coyote Basin, which spans Colorado and Utah, northern Chihuahua, Mexico, and Grasslands National Park, Canada.
Historically, black-footed ferrets lived in habitats such as shortgrass prairie, mixed-grass prairie, desert grassland, shrub steppe, sagebrush steppe, mountain grassland, and semi-arid grassland. These animals use prairie dog burrows to care for their young, avoid predators, and stay warm or cool. Six black-footed ferret nests found near Mellette County, South Dakota, were covered with buffalo grass, prairie threeawn, sixweeks grass, and cheatgrass. Areas with many prairie dog burrows provide the most cover for black-footed ferrets. Black-tailed prairie dog colonies have more burrows per acre than white-tailed prairie dog colonies and may be better for black-footed ferret recovery. The type of prairie dog burrow may affect whether black-footed ferrets live there. Litters of black-footed ferrets near Meeteetse, Wyoming, were found in mounded white-tailed prairie dog burrows, which are less common than non-mounded burrows. Mounded burrows have multiple entrances and likely have deep, extensive tunnels that protect young. However, black-footed ferrets used non-mounded prairie dog burrows (64%) more often than mounded burrows (30%) near Meeteetse, Wyoming.
Mortality
The main reasons for the death of black-footed ferrets are the loss of their homes, diseases brought by humans, and poisoning from efforts to control prairie dogs. Between 59% and 83% of black-footed ferrets (128 total) died each year over four years near Meeteetse, Wyoming. During fall and winter, 50–70% of young and adult ferrets die. In the wild, these ferrets likely live only one year, but some may live up to five years. Male ferrets are more likely to die than females because they travel farther when they are most at risk from predators.
Black-footed ferrets rely completely on prairie dogs for survival, making them very vulnerable when prairie dog habitats are lost. Habitat loss happens because of farming, raising livestock, and other types of development.
These ferrets are at risk from many diseases. They can die from canine distemper virus, which is spread by striped skunks, raccoons, foxes, coyotes, and badgers. A short-term vaccine for canine distemper is used for ferrets in captivity, but wild young ferrets are not protected. They are also at risk from rabies, tularemia, and human influenza. Ferrets can directly catch sylvatic plague (Yersinia pestis), and outbreaks of this disease in prairie dog areas can destroy the food supply for ferrets.
Predators of black-footed ferrets include golden eagles, great horned owls, coyotes, badgers, bobcats, prairie falcons, ferruginous hawks, and prairie rattlesnakes.
Oil and natural gas exploration and drilling can harm prairie dogs and black-footed ferrets. Earthquakes caused by drilling can collapse prairie dog burrows. Other problems include possible leaks and spills, more roads and fences, more vehicles and people, and more places for birds of prey to perch on power lines. Traps set to catch coyotes, mink, and other animals may also harm black-footed ferrets.
History
Native American tribes, including the Crow, Blackfoot, Sioux, Cheyenne, and Pawnee, used black-footed ferrets for religious ceremonies and as a food source. The species was not seen during the Lewis and Clark Expedition or by scientists like Nuttall or Townsend. It was not known to modern science until 1851, when John James Audubon and John Bachman described it in their book Viviparous Quadrupeds of North America.
For a time, black-footed ferrets were hunted for their fur. The American Fur Company received 86 ferret skins from a company in St. Louis in the late 1830s. Later, during predator control efforts, ferret carcasses were often discarded because their fur had little value. This practice likely continued after the Endangered Species Act was passed in 1973, as people feared punishment. Ferret numbers dropped sharply during the 1800s and 1900s because prairie dog populations declined due to human activities like farming and predator control programs.
A disease called sylvatic plague, caused by a germ called Yersinia pestis, also harmed prairie dogs. Ferrets declined more than prairie dogs, suggesting other factors were involved. Plague was first found in South Dakota in a coyote in 2004 and in prairie dogs on the Pine Ridge Reservation in 2005. In 2006–2007, scientists treated 7,000 acres of prairie dog habitat and 1,000 acres of ferret habitat with insecticide and vaccine. Plague was confirmed in ferrets in 2008. Since then, scientists have dusted 12,000 acres of habitat yearly and vaccinated about 50–150 ferrets. Ferrets are unlikely to survive plague outbreaks without management efforts that help them access prey or reduce disease spread. A 2023 study showed that using insecticide and distributing oral vaccines improved prairie dogs’ resistance to plague, which helps ferrets recover. Scientists say large-scale efforts are needed to keep prey and ferret habitats healthy.
Low genetic diversity may have also hurt ferret populations. Studies on ferrets in Wyoming showed they had little genetic variation. A disease called canine distemper killed many ferrets in 1985. A vaccine made for domestic ferrets accidentally killed many black-footed ferrets, showing they are very sensitive to this disease.
Black-footed ferrets faced a major population drop in the wild, followed by a 30-year recovery through breeding in captivity and reintroduction to their natural habitat. This species helps scientists study how limited genetic diversity affects reproduction and survival. The U.S. Fish and Wildlife Service listed the ferret as endangered in 1967. It was declared extinct in 1979, but a small group was found in Wyoming in 1981. This group grew to 130 individuals but was nearly wiped out by plague and distemper, leaving only 18. These 18 were used to start a breeding program. Seven of them had offspring that survived and became ancestors of all ferrets in captivity and the wild today.
A breeding program began in 1987, using artificial insemination to help ferrets reproduce. This was one of the first times assisted reproduction helped save an endangered species. Since 1991, agencies, zoos, and landowners have reintroduced ferrets to the wild in places like Wyoming, Montana, South Dakota, Arizona, Utah, Colorado, Canada, and Mexico. The Toronto Zoo bred many ferrets, most of which were released. In 2009, 35 ferrets were released into Grasslands National Park in Canada, and baby ferrets were seen there in 2010.
The black-footed ferret was first listed as endangered in 1967 and again in 1974. In 2006, South Dakota had about 420 ferrets, with 250 in one area. Arizona had over 100 ferrets, and other reintroduction sites had smaller groups. A 2007 study found 223 ferrets in Wyoming, with a 35% growth rate from 2003 to 2006. This recovery is faster than for many endangered species. By 2007, over 650 ferrets lived in the wild, plus 250 in captivity. In 2008, the IUCN classified the species as "globally endangered," an improvement from its 1996 status as extinct in the wild. In 2016, the species was considered "Critically Imperiled" by NatureServe.
By 2013, about 1,200 ferrets lived in the wild. These populations grew because of breeding programs that released extra animals into the wild, which are monitored by scientists. However, ferrets in captivity have had declining health signs, like lower pregnancy rates and weaker sperm, likely due to inbreeding.
Conservation efforts have faced opposition from ranchers who traditionally opposed prairie dogs. In 2005, the U.S. Forest Service began…
In popular culture
In 2023, the black-footed ferret appeared on a United States Postal Service Forever stamp as part of the Endangered Species collection. The image on the stamp was taken from Joel Sartore's Photo Ark project. The stamp was presented during a ceremony at the National Grasslands Visitor Center in Wall, South Dakota. The U.S. Census Bureau used the image of the black-footed ferret on a web tool called "Data FERRETT." This tool allowed researchers not working for the government to access unique, anonymized data from people who answered Census surveys, including the Current Population Survey.