Biologists consider black-footed ferrets
to be the most endangered mammal in the
United States. Recently, however, thanks
to aggressive captive-breeding and
reintroduction programs, much progress
has been made toward recovering the
ferret population.
Black-footed ferrets are members of the
weasel family (Mustelidae), a distinction
they share with weasels, martens, fishers,
otters, minks, wolverines and skunks.
Larger than weasels, black-footed ferrets
are long, slender-bodied animals similar in
size to a mink. They are characterized by a
brownish-black mask across the face, a
brownish head, black feet and legs, and a
black tip on the tail. Ferrets’ short, buff-colored
fur becomes lighter on the underside
of their bodies. The middle of the back has
brown-tipped guard hairs that create the
appearance of a dark saddle.
Black-footed ferrets may look like the
ferrets found in pet stores but they are
actually a different species. Both belong to
the weasel family but ferrets sold as pets
evolved in Europe, while endangered black-footed
ferrets evolved in North America.
Possibly black-footed ferrets never were
abundant, but their underground nocturnal
habits make it difficult for biologists to know
for certain. First described by naturalists
John Audubon and James Bachman in 1851,
black-footed ferrets were not sighted again
for 25 years.
Ferrets once were found throughout the
Great Plains, from Texas to southern
Saskatchewan, Canada. Their range
extended from the Rocky Mountains east
through the Dakotas and south through
Nebraska, Kansas, Oklahoma, Texas, New
Mexico and Arizona. Where prairie dogs
were found, so were black-footed ferrets.
Ferrets eat prairie dogs and live in prairie
dogs’ burrows.
Typical wild ferret behavior revolves
around prairie dog towns. Wild ferrets
hunt prairie dogs at night but occasionally
they are active above ground during the
day. This is especially true of the female
ferrets hunting to feed their young. In
search of prey, they move along in loping
bounds from one burrow to the next. When
they make a kill, ferrets may drag prairie
dogs some distance to a home burrow to
devour below ground or to burrows in
which they have their young.
Black-footed ferrets produce about four or
five young once each year. Born in May or
June, the young do not come above ground
until they are six weeks old. Mothers and
young remain together until about mid-
August. At that time, females begin to
separate the siblings into different burrows.
From August through early September the
young become increasingly solitary. By early
October they are able to take care of
themselves.
Main causes of the decline in the ferret
population included habitat conversion for
farming; efforts to eliminate prairie dogs,
which competed with livestock for available
prairie forage; and the sylvatic plague, a
disease which wiped out large numbers of
ferrets.
The U.S. Fish and Wildlife Service listed
black-footed ferrets as endangered in 1967
under a precursor to the Endangered
Species Act of 1973. Endangered means a
species is considered in danger of becoming
extinct in all or a significant portion of its
range; the less dire designation of
threatened means a species is likely to
become endangered within the foreseeable
future throughout all or a significant portion
of its range.
By 1972, biologists believed black-footed
ferrets to be extinct. From 1972 until 1981,
although many ferret sightings were
reported, the only documented population
was found in the 1970s in South Dakota.
Then in 1981, a dog killed an unusual animal
on a ranch in Wyoming. The rancher took it
to a taxidermist who recognized it as a black-
Black-footed ferret
Mustela nigripes
The black-footed ferret probably never was
abundant, but its underground, nocturnal
habits make it difficult for biologists to know
for certain. The ferret’s
primary food source is
the prairie dog, and
ferrets live in the
prairie dog’s burrow.
U.S. Fish & Wildlife Service
footed ferret. This led to the discovery of a
small ferret population near Meeteetse,
Wyoming, in 1981. The population increased
from 1981 through 1984. At its peak in 1984,
nearly 130 ferrets were counted.
In October 1985, the Wyoming Game and
Fish Department, in cooperation with the
Fish and Wildlife Service, captured six
black-footed ferrets to start a captive
breeding population at the Department’s
Sybille Wildlife Research and Conservation
Education Center near Wheatland,
Wyoming (now operated by the Fish and
Wildlife Service as the National Black-footed
Ferret Conservation Center). During the fall
of 1986 and the spring of 1987 the last known
wild black-footed ferrets were taken from
the wild and placed in captive breeding
facilities. This captive population now has
increased to approximately 300 black-footed
ferrets.
The goal of the captive breeding program
is to establish 240 breeding adults in
captivity while continuing to return ferrets
to the wild. In an effort to protect ferrets
from one catastrophic event which could
eliminate the entire experimental wild
population, the captive population was
divided. In addition to the Ferret
Conservation Center colony, breeding
populations have been established at the
National Zoo’s Conservation and Research
Center in Front Royal, Virginia; the Henry
Doorly Zoo in Omaha, Nebraska; the
Cheyenne Mountain Zoological Park in
Colorado Springs, Colorado; the Phoenix
Zoo in Phoenix, Arizona; and the Louisville
Zoological Garden in Louisville, Kentucky.
The future looks brighter for black-footed
ferrets. Reintroduction began in 1991 with
the release of a group of ferrets into the
Shirley Basin of Wyoming. Since then, 228
ferrets have been released there. While
there is a high mortality rate among these
captive-born animals, two litters born in the
wild indicate that the reintroduced
population has taken hold. Biologists
stopped releasing ferrets in the Shirley
Basin after 1995 because of disease concerns
and decreasing habitat.
Two new reintroduction sites in Montana
and South Dakota were identified and
biologists released 40 to 50 ferrets per year
on these sites between 1994 and 1997.
Biologists hope the populations on these
sites will be self-sustaining after 1998. So far
reintroduction efforts in those two states
have met with some success. In 1997, twelve
litters of ferrets were born in the wild in
Montana and reintroduced ferrets in South
Dakota had an 80 percent survival rate.
In 1996 and 1997, biologists identified
suitable release sites in areas in Utah,
Colorado and Arizona. Sixty-five ferrets
have been released in the Aubrey Valley in
northwest Arizona since March, 1996. Some
of the released ferrets have already given
birth in the wild, and biologists plan to
release more ferrets in the same area.
To be considered suitable for ferret
reintroduction, an area must be very large
and relatively free of diseases, particularly
canine distemper and plague, that could wipe
out an entire colony. And the public must
support the presence of black-footed ferrets.
To this end, biologists work closely with
landowners to work out compromises that
benefit the ferret and landowners.
Reintroduced black-footed ferret
populations have been designated “non-essential
experimental” populations under
the Endangered Species Act. This
designation allows federal, state and tribal
resource managers, and private citizens,
more flexibility in managing new
populations. The Service can develop special
management regulations which are more
flexible than the rules for species listed as
endangered, encouraging cooperation in the
recovery effort by landowners, agencies and
recreation interests. The “non-essential,
experimental” designation also allows land
uses such as forest management,
agricultural practices, sport-hunting and
non-consumptive outdoor recreation.
National goals to recover the species are to
establish ten free-ranging populations of
black-footed ferrets, spread over the widest
possible area within their former range.
Each of these populations will have 30 or
more breeding adults. It is hoped that 1,500
free-ranging black-footed ferrets will be
established in the wild by the year 2010.
If these and future efforts are successful,
black-footed ferrets may soon be playing an
important role in the dynamics of wild
prairie dog towns once again.
U.S. Fish & Wildlife Service
1 800/344 WILD
http://www.fws.gov
August 1998
Black-footed ferrets hunt prairie dogs at
night, but occasionally they are active above
ground during the day. In search of prey,
they move along in loping bounds from one
burrow to the next.
