Like most members of the weasel family, the mink has a long, slender body and short legs. The tail is about two-fifths as long as the body. Adult males are longer (21 to 24 inches) and heavier (2 to 3 3/4 pounds) than adult females (16 3/4 to 21 inches; 1 1/4 to 1 3/4 pounds). Most wild mink are dark brown except for a white chin and a tail that's tipped with black. Some have one or more irregular white patches on their throats or chests. A mink's ears are short, barely extending above its fur.
Domestic mink have been bred selectively for many generations to attain a larger size and wider variety of colors than their wild cousins. Trade names like standard, demi-buff, pearl, sapphire, and gunmetal refer to color strains ranging from jet black to pure white and bluish-gray. Domestic mink occasionally escape into the wild, but few survive.
Distribution & Abundance
Mink are found in every county in Illinois. They're most abundant in the glacial lakes area of northeastern Illinois, counties bordering the lower Mississippi River, and the southern third of the state. While they still are common, wild mink are less abundant than they were 50 to 100 years ago because of habitat loss caused by development, stream channelization and drainage of wetlands.
Mink live along rivers, streams, lakes, ponds and marshes. Shorelines with grass, brush, trees or aquatic vegetation like cattails provide good cover and abundant prey. Abandoned burrows dug by muskrats are their favorite places to rest and raise young, but they will use cavities in brush or rock piles, logjams and the exposed roots of trees. A den can have several entrances, and includes a nest chamber about 1 foot in diameter that is sometimes lined with grass, leaves, fur or feathers.
Mink are mostly nocturnal --active from dusk to dawn. Nearly all of their time is spent within 100 feet of the water's edge, but they'll occasionally cut across open country from one body of water to another. During winter, they often stay in their dens during periods of extreme cold or heavy snow cover, but they don't hibernate. Mink live alone except when raising their young.
Male mink travel extensively, moving from one temporary den to the next in an area as large as 5 square miles. They may take as long as two to three weeks to visit many of the waterways in this area before completing their circuit and returning to the area where they started. Females live in a much smaller area, usually 20 to 50 acres in size. They often use a single den during the entire year.
Mink are well adapted to traveling on land and in water. On land, they usually walk or take low bounds of 10 to 24 inches in length, traveling at speeds of up to 7 to 8 miles per hour. Mink often rear up on their hind legs for a better look at their surroundings. When disturbed, they enter the nearest shelter and frequently escape by climbing trees. Mink can swim as far as 50 feet underwater and reach surface speeds of 1 to 1.5 miles per hour.
The mink is extremely aggressive and capable of attacking and killing animals much larger than itself. Fights with other mink are common, especially when populations are high. Mink rely heavily on smell to locate prey while on land. Most often they kill their prey with a bite to the neck
Mink are carnivores (flesh-eaters). Frogs, mice, rats, fish, rabbits, crayfish, birds, squirrels and muskrats are common food items. Large prey such as rabbits are often carried to a den before they're eaten. Leftovers may be stored, but often spoil before they're eaten entirely.
Mink are capable of breeding at 10 to 12 months of age. Mating usually takes place in February or March. Males mate with many different females. They occasionally remain with the last female to assist in caring for the young.
An average of 51 days passes between mating and the birth of young. However, this can be as short as 40 days or as long as 75 days because of a process called delayed implantation. This phenomenon is common among members of the weasel family, and involves a dormant period between the time the egg is fertilized and the time it begins to develop into a fetus. In general, the earlier that mating takes place, the longer the delay before embryos begin to develop. Young females and those with smaller litters also tend to have longer pregnancies.
A single litter of two to seven young (an average of four) is born around the first of May. Newborns are blind, lack hair and about 3 1/2 inches in length. In two weeks they grow fuzzy, reddish-gray hair. Their eyes open at about 5 weeks of age. Kits start learning how to hunt at 6 to 8 weeks of age, and can care for themselves by late summer.
Mink can be trapped during a legal season for about two months during the fall and early winter. The length of the season ensures that populations are protected from overharvest. The season occurs when mink pelts are at their best quality and ensures that no babies or mothers with dependent young are taken.
Habitat protection and enhancement are the most important management practices for sustaining healthy populations. Some of these include:
Wetland protection and restoration (creating new wetlands): this provides favorable habitat for mink and other wildlife, stores water during flood events and purifies ground and surface water.
Managed grazing: restricting livestock access along streams and rivers helps to maintain natural vegetation by reducing grazing and trampling. This provides habitat for mink and other wildlife, reduces erosion of stream banks and prevents siltation. (Siltation occurs when soil particles are washed into the water. The soil particles eventually settle to the bottom of the stream or river, filling in areas with slow-moving water and covering portions of a streambed that had been rock, sand, or gravel. Many types of fish need rock, sand or gravel bottoms to lay their eggs and raise young. Covering up these areas with silt means fewer fish to provide food for mink.)
Conservation tillage: this refers to farming practices that leave crop residue (stems and leaves) on the soil surface. These practices reduce erosion, helping to improve water quality by keeping chemicals and soil particles from washing into streams and rivers.
- Filter strips and grass waterways: filter strips are areas next to a stream or river that have been planted to natural vegetation like grass or trees. The plants' roots help to hold soil in place and remove chemicals as water passes through the filter strip toward a stream or river. Above-ground portions of plants help to filter water by trapping soil particles suspended in it. Grass waterways act in the same way, but are planted in low spots that collect water as it runs downhill toward the filter strip. Filter strips and grass waterways not only improve water quality, but provide good areas for mink to hunt mice and other small rodents.