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Nebraska Wildife
Species Guide
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Mink
Habitat
Foods
Mortality
Importance
Description
The common name mink comes from the Swedish word maenk. Mink are members of
the weasel family which includes skunks, otters, fishers, martens and
wolverines.
The mink has a long narrow body, short legs and a relatively
long tail. Its head is flattened and it has a short pointed snout,
small eyes and short rounded ears. An adult male may be 30
inches long and weigh up to three and a half pounds, and a female is typically
two-thirds that size.
The mink's coloration varies from brown to almost black, its
belly is slightly lighter than its back and flanks, and it may have
a white chin and throat. A domestic mink raised on a ranch for
the fur industry is normally much larger than a wild mink and the color
of its fur ranges from white to black with several unique
colors that have been developed by mink ranchers. A mink's pelt
has thick underfur for insulation and buoyancy because the
animal lives in and near water. However, it does not have
webbed feet or a specialized tail as do other semi-aquatic mammals
such as beaver, muskrats and otters.
A mink has highly developed anal scent glands, which is
typical of members of the weasel family. The mink is not as
adept at spraying with these glands as are skunks, but the odor
of the secretions is just as obnoxious.
Distribution and abundance
Mink are found thoughout North America, northern Europe and the Soviet
Union. In Nebraska, mink are found statewide where suitable riparian
habitat, such as riverbanks and lake shores, occur. They are most
common in the Sandhills in north-central Nebraska, the Rainwater Basin area in the south-central portion of the state, and
along major river systems.
Habitat and home
The mink lives in a variety of wetland
and riparian habitats including rivers, streams, lakes, ponds and
marshes. Permanent water, a reliable food source and adequate
shoreline vegetation are keys to good mink habitat Upland
vegetation around the stream or wetland is also important to the
mink, because it frequently hunts as much as one-quarter mile
away from the water. Intensive farming or grazing to the edge
of the shoreline or stream bank reduces the quality of mink
habitat because it eliminates necessary hunting sites. Stream
channelization reduces the amount of habitat available by reducing
the length of the stream, and erosion reduces the quality of
habitat for fish and other prey. Another way in which mink
habitat is commonly destroyed is by people draining and filling
wetlands, or allowing too much grazing of wetlands. In many
areas of Nebraska where habitat has been destroyed, mink numbers
have declined. Mink make their homes in abandoned
muskrat lodges and burrows, and in natural cavities in stream
banks, under trees and in drift piles. Mink frequently line their
dens with grass, leaves, fur or feathers.
Habits
A male mink travels widely and may occupy as much
as 2.5 miles of stream habitat or about 2500 acres in wetland
habitat. An adult female generally travels less and occupies
about one mile of stream habitat or about 40 acres in wetland
habitat. A male increases its movement greatly during the breeding
season and defends its territory against other males, although
the males' home ranges sometimes overlap. A male may use
several dens within its range and different males may use the
same den at different times. A female defends her territory
against other females and may even defend it against males at
certain times of the year. She usually has one or two dens and is
the only one to use them. Juveniles that have recently left the
family group often use several dens until they establish their own
home range, which are usually smaller than those of older mink.
The number of mink in an area usually depends on the amount
and quality of available habitat, but there is usually about one
mink for each 50 acres of wetland habitat and three or four mink
for each mile of good stream habitat.
While a mink may be active all day long, it is most active from
dusk to dawn. It is active year-round although it may remain in
its den for a day or two during severe winter weather. A mink
usually lives alone except during the breeding season and when
young mink live with the family group until they are old enough
to claim their own territories.
The mink marks its territory and advertises its presence by
depositing droppings and leaving its scent in prominent locations
such as on flat rocks and logs.
A mink is an aggressive predator and often attacks animals
larger than itself. While a mink is curious of its surroundings, it
has only fair eyesight and tends to rely on its sense of smell to
locate prey. Although the mink lives in a wetland habitat, it is
not well adapted for swimming, so it concentrates its search for
food to upland areas near the water, along shorelines or in
shallow water. It kills most of the small animals, birds and fish
it feeds on by biting them at the base of the skull or the nape of
the neck.
Foods
The mink feeds on a wide variety of terrestrial
animals such as mice, rabbits and muskrats; small birds; and
several aquatic animals, including frogs, fish and crayfish, and
seldom eats insects or carrion. Prey are usually killed then taken
to the den to be eaten. Mink sometimes store food away for later
use. The wide variety of prey the mink eats may reduce competition
for food widh more specialized predators like otters and
weasels. The difference in size between the male and female
mink further reduces competition for food because the male
tends to prey on larger animals like rabbits, large birds and
muskrats, while the female chooses smaller animals like mice
and small birds.
Reproduction
The mink's breeding season is influenced by
lengthening days during the spring and occurs in February-April
in Nebraska. A male will mate widh several females during the
breeding season. There are four or five young in a normal litter,
but litters may be smaller in first-year breeders. Reproductive
success may vary widely from year to year, based on habitat
conditions. The young weigh less than one-half ounce when they
are born, but they grow and develop rapidly. Young females are
fully grown by the following fall while males continue to grow
into their second year. The family group remains together until
late summer when juvenile dispersal begins. The larger males
disperse first, while juvenile females may not disperse until the
following spring. The young mink may move as far as 10 miles
from the birth area.
Mortality
The average lifespan of a mink is less than one
year and it is uncommon for them to live as long as four years.
Mink are preyed upon by owls, coyotes and cats. Other significant
sources of mortality include fighting with other mink,
starvation of dispersing juveniles, and trapping.
Because male mink range farther, the harvest of mink is
typically skewed toward males, which generally make up 65 to 75
percent of the annual fur harvest. Juveniles of both sexes are
more abundant and more vulnerable to trapping than adults, and
juveniles usually comprise about 60 percent of the annual fur
harvest.
As a predator in wetland habitat, mink accumulate unwanted
chemicals in their systems. Mink can be used as barometers of
the environment because the levels of chemicals in their tissues
reflect the levels of those chemicals in the environment. In some
areas of the United States, reductions in mink numbers have been
blamed on high levels of harmful chemicals in the environment.
High levels of chemicals usually result in smaller litters and
poorer survival of young animals.
Importance
Because they are small and secretive, mink are
seldom seen by humans, though they will occasionally raid a
chicken house and will prey on nesting waterfowl. Domestic
mink raised on ranches are a staple of the fur industry and the
pelts of wild mink are highly valued. From 1941-89, Nebraska
trappers took nearly 390,000 mink. Harvest totals from 1980-89
indicate an average annual harvest of 6,400 mink valued at over
$121,000. In Nebraska, most mink are likely taken in traps set
for other furbearers such as muskrat, raccoon and beaver. Even
though they are curious, mink are quite wary and few trappers become
proficient at taking them, which explains why beginning trappers view
catching a mink a sizable accomplishment.
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