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The muskrat (Ondatra zibethicus) is the largest microtine rodent in the United States. It spends its life in aquatic habitats and is well adapted for swimming. Its large hind feet are partially webbed, stiff hairs align the toes, and its laterally flattened tail is almost as long as its body. The muskrat has a stocky appearance, with small eyes and very short, rounded ears. Its front feet, which are much smaller than its hind feet, are adapted primarily for digging and feeding. The overall length of adult muskrats is usually from 18 to 24 inches (46 to 61 cm). Large males, however, will sometimes be more than 30 inches (76 cm) long, 10 to 12 inches (25 to 31 cm) of which is the laterally flattened tail. The average weight of adult muskrats is from 1 1/2 pounds (0.7 kg) to over 4 pounds (1.8 kg), with most at about 2 1/2 pounds (1.1 kg).
The range of the muskrat extends from near the Arctic Circle in the Yukon and the Northwest Territories, down to the Gulf of Mexico, and from the Aleutians east to Labrador and down the Atlantic coast into Georgia. The muskrat has been introduced practically all over the world, and, like most exotics, has sometimes caused severe damage as well as ecological problems. Muskrats often cause problems with ponds, levees, and crop culture, whether introduced or native. Muskrats are found in most aquatic habitats throughout the United States and Canada in streams, ponds, wetlands, swamps, drainage ditches, and lakes.
Exclusion: Riprap the inside of a pond dam face with rock, or slightly overbuild the dam to certain specifications.
Cultural Methods and Habitat Modification: Eliminate aquatic vegetation as a food source. Draw down farm ponds during the winter months.
Frightening: Seldom effective in controlling serious damage problems.
Repellents: None are registered.
Toxicants: Zinc phosphide. Anticoagulants (state registrations only).
Trapping: Body-gripping traps (Conibear® No. 110 and others). Leghold traps, No. 1, 1 1/2, or 2. Where legal, homemade “stove pipe” traps also are effective when properly used.
Shooting: Effective in eliminating some individuals.
Other Methods: Integrated pest management.