Identification

The mink (Mustela vison, Fig. 1) is a member of the weasel family. It is about 18 to 24 inches (46 to 61 cm) in length, including the somewhat bushy 5- to 7-inch (13- to 18-cm) tail, and weighs 1 1/2 to 3 pounds (0.7 to 1.4 kg). Females are about three-fourths the size of males. Both sexes are a rich chocolate-brown color, usually with a white patch on the chest or chin and scattered white patches on the belly. The fur is relatively short with the coat consisting of a soft, dense underfur concealed by glossy, lustrous guard hairs. Mink also have anal musk glands common to the weasel family and can discharge a disagreeable musk if frightened or disturbed. Unlike skunks, however, they cannot forcibly spray musk.

Range and Habitat

Mink are found throughout North America, with the exception of the desert southwest and tundra areas (Fig. 2).

Mink are shoreline dwellers and their one basic habitat requirement is a suitable permanent water area. This may be a stream, river, pond, marsh, swamp, or lake. Waters with good populations of fish, frogs, and aquatic invertebrates and with brushy or grassy ungrazed shorelines provide the best mink habitat. Mink use many den sites in the course of their travels and the availability of adequate den sites is a very important habitat consideration. These may be muskrat houses, bank burrows, holes, crevices, log jams, or abandoned beaver lodges.

Food Habits

The mink is strictly carnivorous. Because of its semiaquatic habits, it obtains about as much food on land as in water. Mink are opportunistic feeders with a diet that includes mice and rats, frogs, fish, rabbits, crayfish, muskrats, insects, birds, and eggs.

General Biology, Reproduction, and Behavior

Mink are polygamous and males may fight ferociously for mates during the breeding season, which occurs from late January to late March. Gestation varies from 40 to 75 days with an average of 51 days. Like most other members of the weasel family, mink exhibit delayed implantation; the embryos do not implant and begin completing their development until approximately 30 days before birth. The single annual litter of about 3 to 6 young is born in late April or early May and their eyes open at about 3 weeks of age. The young are born in a den which may be a bank burrow, a muskrat house, a hole under a log, or a rock crevice. The mink family stays together until late summer when the young disperse. Mink become sexually mature at about 10 months of age.

Fig. 2. Distribution of mink in North America.

Mink are active mainly at night and are active year-round, except for brief intervals during periods of low temperature or heavy snow. Then they may hole up in a den for a day or more. Male mink have large home ranges and travel widely, sometimes covering many miles (km) of shoreline. Females have smaller ranges and tend to be relatively sedentary during the breeding season.

Damage and Damage Identification

Mink may occasionally kill domestic poultry around farms. They typically kill their prey by biting them through the skull or neck. Closely spaced pairs of canine tooth marks are sign of a mink kill.

Mink will attack animals up to the size of a chicken, duck, rabbit, or muskrat. While eating muskrats, a mink will often make an opening in the back or side of the neck and skin the animal by pulling the head and body through the hole as it feeds. Like some other members of the weasel family, mink occasionally exhibit “surplus killing” behavior (killing much more than they can possibly eat) when presented with an abundance of food, such as in a poultry house full of chickens. Mink may place many dead chickens neatly in a pile. Mink can eat significant numbers of upland nesting waterfowl or game bird young, particularly in areas where nesting habitat is limited.

Legal Status

Mink are protected furbearers in most states, with seasons established for taking them when their fur is prime. Most states, however, have provisions for landowners to control furbearers which are damaging their property at anytime of the year. Check with your state wildlife agency before using any lethal controls.

Damage Prevention and Control Methods

Mink damage usually is localized. If needed, lethal controls can be directed at the individual mink causing the damage.

Exclusion

Usually the best solution to mink predation on domestic animals is to physically exclude their entry, sealing all openings larger than 1 inch (2.5 cm) with wood or tin and by using 1-inch (2.5-cm) mesh poultry netting around chicken yards and over ventilation openings. Mink do not gnaw like rodents, but they are able to use burrows or gnawed openings made by rats.

Habitat

Modification Habitat modification generally is not a feasible means of reducing mink predation problems on farms. If the objective is to increase natural production of upland nesting wild birds, however, habitat modification may be applicable. The best method of increasing upland nesting success is usually to increase the size and quality of cover areas such as grasslands, legumes, or set-aside areas. Although increasing the density of nesting cover may reduce nest predation by mink, it could lead to an increase in nest predation by species which favor dense cover, such as the Franklin ground squirrel. Because mink frequently use multiple den sites, elimination of potential denning areas may reduce their densities.

Frightening

There are no known frightening devices that are effective for deterring mink predation.

Repellents, Toxicants, and Fumigants

There are no repellents, toxicants, or fumigants registered for mink damage control.

Trapping

Mink can most easily be captured in leghold traps (No. 11 double long-spring or No. 1 1/2 coilspring) or in Conibear®-type body-gripping traps equivalent to No. 120 traps. Mink are suspicious of new objects and are difficult to capture in live traps. Single-door live traps may be effective if baited and placed in dirt banks or rock walls. Double-door live traps can be effective in runways, particularly if the trap doors are wired open and the trap is left in place for some time before activating the trap. Live traps may also be effective around farmyards because mink are more accustomed to encountering human-made objects in those areas.

“Blind sets” are very effective for mink if suitable locations can be found. These sets do not require bait or lures and are placed in areas along mink travel lanes where the animals are forced to travel in restricted areas (Fig. 3). Good sites for blind sets include small culverts, tiles, narrow springs, muskrat runs, and areas under overhanging banks or under the roots of streamside trees (Fig. 4). If necessary, the opening can be restricted with the use of a few sticks or grass to direct the mink over the trap.

Another good mink set is the “pocket set” using bait (Fig. 5). This set is made by digging a 3-inch (7.6-cm) diameter hole horizontally back into a bank at the water level. The bottom of the hole should contain about 2 inches (5 cm) of water, and it should extend back at least 10 inches (25 cm) into the bank. Place a bait (fresh fish, muskrat carcass, or frog) in the back of the hole above water level and place the trap underwater at the opening of the hole. Traps should be solidly staked and connected to a drowning wire leading to deep water.

Fig. 3. An obstruction set catches a mink where it is traveling along the bank and is forced into the water. Disturbance at the trap site should be kept to a minimum.

Fig. 4. The spring set catches the mink where a small feeder stream or tile outlet enters a larger stream or impoundment.

Fig. 5. The pocket set is effective for mink. Bait or lure is placed in the back of the hole above the water level. (Note: the stake is set off to one side and its top should be driven below the water line).

Use live traps around a farmyard if there is a high likelihood of catching pets. Otherwise, leghold or Conibear® traps can be used with or without bait in runs or holes used by mink.

Shooting

Some states may have restrictions on shooting mink, although many will make exceptions in damage situations. If a mink is raiding poultry and can be caught in the act, shooting the animal is a quick way to solve the problem. Normally, though, it is difficult to shoot mink because of their nocturnal habits.

Economics of Damage and Control

Although an individual incident of mink predation can be costly, overall the problem is not very significant to agriculture. Mink damage control on a case-by-case basis generally can be justified from a cost/benefit standpoint, but large-scale control programs are neither necessary nor desirable. Exclusion procedures may or may not be economically justifiable, depending on the severity of the problem and the amount of repairs needed. Normally, such costs can be justified for a recurring problem when amortized over the life of the exclusion structures. Usually damage from other predators and rodents is reduced as well.

Mink are important semiaquatic carnivores in wetland wildlife communities, and are also valuable as a fur resource. About 400,000 to 700,000 wild mink are harvested each year throughout North America, for an annual income exceeding $5 million. Therefore, all lethal control should be limited to specific instances of documented damage.

Acknowledgments

Information for this section came from a variety of published and unpublished sources. Information on damage identification was adapted from Dolbeer et al. (1994).

Figures 1 and 2 from Schwartz and Schwartz (1981).

Figures 3, 4, and 5 by Michael D. Stickney, from the New York Department of Environmental Conservation publication, Trapping Furbearers, Student Manual (1980), by R. Howard, L. Berchielli, C. Parsons, and M. Brown. The figures are copyrighted and are used with permission.

For Additional Information Dolbeer, R. A., N. R. Holler, and D. W. Hawthorne. 1994. Identification and control of wildlife damage. Pages 474-506 in T. A. Bookhout, ed. Research and management techniques for wildlife and habitats. The Wildl. Soc., Bethesda, Maryland.

Eagle, T. C., and J. S. Whitman. 1987. Mink. Pages 614-625 in M. Novak, J. A. Baker, M. E. Obbard, and B. Mallock, eds. Wild furbearer management and conservation in North America. Ontario Trappers Assoc. and Ontario Ministry Nat. Resour.

Linscombe, C., N. Kinler, and R. J. Aukrich. 1982. Mink. Pages 629-643 in J. A. Chapman and G. A. Feldhamer, eds. Wild mammals of North America: biology, management, and economics. The Johns Hopkins Univ. Press, Baltimore, Maryland.

Schwartz, C. W., and E. R. Schwartz. 1981. The wild mammals of Missouri. rev. ed. Univ. Missouri Press, Columbia. 356 pp.

Editors

Scott E. Hygnstrom Robert M. Timm Gary E. Larson

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994

Cooperative Extension Division Institute of Agriculture and Natural Resources University of Nebraska -Lincoln

United States Department of Agriculture Animal and Plant Health Inspection Service Animal Damage Control

Great Plains Agricultural Council Wildlife Committee

Special thanks to:
Clemson University