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 3 Ih 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 Rain water 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. The mink usually lines its den will 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 minks, 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.