Overview
The black-footed ferret, Mustela nigripes, is a medium-sized carnivore in the mustelid family, a group of carnivorous mammals that includes weasels, badgers, martens, mink and otters, among others. It is the only ferret species native to the Americas, as noted by the U.S. Fish and Wildlife Service, 2019. The earliest fossil record of the black-footed ferret is from approximately 100,000 years ago, according to Anderson et al., 1986, and Clark, 1986. Black-footed ferrets were first described in 1851 from a specimen observed near the Platte River by J.J. Audubon and J. Bachman, as noted by Anderson et al., 1986, and Clark 1986.
Anderson et al. estimated that in the late 1800s, there may have been 500,000 to 1 million black-footed ferrets. Near the end of the late 1950s, black-footed ferrets were presumed extinct throughout their range as a result of landscape alterations from agricultural expansion and prairie dog eradication. In 1964, however, a small population of ferrets was discovered in Mellette County, South Dakota. This population was used in captive breeding efforts that were ultimately unsuccessful, and that wild population died out in 1974. Then in 1979, what was thought to be the last ferret died in captivity. In 1981, ferrets were rediscovered near Meeteetse, Wyoming, which launched the Black-Footed Ferret Recovery Program. Lockhart et al., 2006, note that black-footed ferrets were extirpated from the wild in 1987 to initiate a captive breeding program.
The U.S. Fish and Wildlife Service listed the black-footed ferret as an endangered species under the early endangered species legislation on March 11, 1967,32 FR 4001, and again on June 2, 1970, 35 FR 8491. The ferret was grandfathered into the Endangered Species Act in 1973. The National Black-Footed Ferret Conservation Center was established in 2001 near Fort Collins, Colorado. It hosts the largest captive population of black-footed ferrets, and supplies them for reintroduction efforts, as noted by the agency. Colorado is home to a second captive breeding facility – the Cheyenne Mountain Zoo in Colorado Springs. The other captive breeding facilities are:
1. Smithsonian Conservation Biology Institute in Front Royal, Virginia
2. Louisville Zoological Garden in Louisville, Kentucky
3. Phoenix Zoo in Phoenix, Arizona
4. Toronto Zoo in Toronto, Ontario, Canada
The U.S. Fish and Wildlife Service in 2019 noted that the four primary stressors to black-footed ferrets are disease, drought, declining genetic fitness including increased inbreeding and a reduction in genetic diversity, and prairie dog poisoning and shooting. The main disease concern for wild and captive populations is non-native sylvatic plague. In fact, the agency says it is the most significant challenge to ferret population resiliency. Canine distemper affects wild and captive populations too, but due to reduced prevalence and vaccination efforts, no canine distemper epizootics have been observed since 1991; therefore, the threat of this virus on ferrets is greatly reduced. Captive populations are also affected by other native diseases, including coccidiosis, cryptosporidiosis and hemorrhagic syndrome, according to Hutchins et al., 1996. The U.S. Fish and Wildlife Service notes that such native diseases may occur in the wild, but they are uncommon.
Scientific Name
Identification Numbers
Characteristics
Habitat
Black-footed ferrets inhabit the intermountain prairies and grasslands. Forrest et al., 1985, found that black-footed ferrets do not appear to be influenced by vegetation composition, but rather, by the presence of prairie dogs. Hillman and Clark, 1980, noted that ferrets are obligate associates of prairie dogs. Ferrets do not dig their own burrows and instead modify existing burrows created by prairie dogs, according to Hillman,1968, and Biggins et al., 2006. As a result, ferrets typically select areas within prairie dog colonies that contain high burrow densities. Ferrets generally need large, contiguous prairie dog colonies.
Land on which the natural dominant plant forms are grasses and forbs.
Food
The favored prey item of ferrets is prairie dogs, according to Hillman,1968, and Biggins et al., 2006. However, they have greater foraging plasticity than previously reported. Prairie dogs made up 75% of the diets of adult males and juvenile ferrets, and approximately 66% of the diets of adult females, noted Brickner et al., 2014. They documented adult female ferrets obtaining over one-third of their diet from other species, primarily mice. Richardson et al., 1987, documented Nuttall’s cottontail, Sylvilagus nuttallii, and deer mice, Peromyscus maniculatus, as prey eaten by black-footed ferrets.
Behavior
Black-footed ferrets are an elusive species, so much so that there were doubts about their existence after their initial description in the scientific community. This species is difficult to observe because it is nocturnal and lives underground, as noted by Anderson et al., 1986, and Clark 1989. Clark, 1986, noted black-footed ferrets appear above ground at irregular intervals and for irregular durations. Eads et al., 2012, note they are typically active on nights when the moon is above the horizon; however, they have occasionally been observed during the day, according to Clark et al., 1986; Eads et al., 2010; and Livieri et al., 2013.
Watch black-footed ferret behaviors on live cams at the Fort Collins Museum of Discovery in Colorado!
Physical Characteristics
Black-footed ferrets are approximately 19 to 24 inches, or 48 to 61 centimeters, in length, according to Hillman and Clark, 1980, and Anderson et al., 1986.
Black-footed ferrets can weigh 1.4 to 2.5 pounds, or 635 to 1134 grams, according to Hillman and Clark, 1980, and Anderson et al., 1986.
The fur of the black-footed ferret is black on the feet and tail tip, with a distinctive mask across the eyes. Fur on the upper body is yellowish buff, occasionally whitish as noted by Hillman and Clark, 1980, and Anderson et al., 1986.
Life Cycle
Mustelids like the black-footed ferret in general have short mean life expectancies, with 50% or greater juvenile mortality, according to Clark, 1989. Black-footed ferret females and males in the wild live to 5 and 4 years of age, respectively. The mean life expectancy of free-ranging ferrets at the last known wild population of ferrets near Meeteetse, Wyoming, was 0.9 years, noted Biggins et al., 2006. In the Conata Basin of South Dakota, McDonald et al, 2005, found the annual survival rates were 70% for juvenile females, 50% for adult females and 38% for males, regardless of age.
Black-footed ferrets are solitary species, except for the purposes of reproduction and when females are raising young, according to Forrest et al., 1985. The breeding season begins when a ferret is approximately 1 year old, from mid-March through early April, as noted by Wilson and Ruff, 1999. They note that gestation takes approximately 42 to 45 days, culminating in an underground birth of three to four kits. Kits are born altricial; they are helpless, requiring parental care, and their eyes do not open until 37 days post-birth, according to Vargas and Anderson, 1996. Mothers will frequently move litters to other burrows within their use areas, and will also reuse burrows previously occupied by their litters, as noted by Forrest et al., 1985. Vargas and Anderson found that kits reach adult weight after 125 days; young typically become mature enough to move aboveground in July, or at about 60 days of age, according to Forrest et al. They note that dispersal of young from natal dens occurs at approximately 100 days of age in the months of autumn, and there is documentation of some adults dispersing at that time of year as well.
Geography
The black-footed ferret is endemic to North America and was historically found across the Great Plains, mountain basins and semi-arid grasslands in 12 states: Arizona, Colorado, Kansas, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Utah and Wyoming, according to the U.S. Fish and Wildlife Service, 2019. Additionally, the agency notes, their historical range includes the Canadian province of Saskatchewan and the Mexican state of Chihuahua. Range and habitat of black-footed ferrets coincides with the ranges of three species of prairie dogs: the black-tailed prairie dog, Cynomys ludovicianus; Gunnison’s prairie dog. C. gunnisonii; and the white-tailed prairie dog. C. leucurus, according to Hillman and Clark, 1980.
On August 21, 1991 (56 FR 41473), portions of Arizona, Colorado, Montana, South Dakota and Utah were designated as non-essential experimental populations, which accounts for the locations where most reintroduced black-footed ferrets have been released. Under Section 10(j) of the Endangered Species Act, a listed species reintroduced outside of its current range, but within its historical range, may be designated as “experimental,” and allows for flexibility by the U.S. Fish and Wildlife Service in managing these populations as noted by the agency in 2013. Currently, known ferret populations are all a result of reintroduction efforts. The largest population of reintroduced ferrets, with an average estimate of 100 breeding adults in 2012, occurs at the Shirley Basin site near Medicine Bow, Wyoming, according to the agency.
Timeline
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