Wetland Management: Mammals in Wetlands

There are several kinds of mammals that thrive in wetlands. The two that have the most influence on wetland plants and, hence, on the entire ecosystem are the muskrat and beaver.

Muskrats primarily feed on aquatic plants. Their feeding habits can help wetland managers maintain the proper proportion of open water and vegetation for waterfowl. Too much muskrat activity, however, can destroy the aquatic vegetation on which they and other wildlife depend. Fortunately, such "eat-outs" are not common in Missouri.

Image Right: Muskrats thrive in wetlands. Their feeding habits can help control the amount of open water and vegetation in a wetland, but can also destroy the aquatic vegetation on which they and other wildlife depend. Trapping can help control muskrats and prevent destructive burrowing by these animals.

Because the muskrat's reproductive capacity is great, in most aquatic environments the animal can withstand heavy trapping. Muskrat trapping helps create and maintain the proper habitat for wildlife and the fur from this extremely renewable resource is a valuable product. Perhaps the muskrat is most troublesome because of its digging and burrowing. Many marsh-dwelling muskrats live in lodges made from marsh plants, but in manmade wetlands, ponds and creeks, bank burrowing is normal. Fluctuating water levels aggravate burrowing problems by forcing the animals to continually dig to keep their living quarters above the water level. Vehicles or livestock can collapse the burrows, further damaging the levee or dam. Trapping is the best tool for controlling muskrat damage in severe burrowing situations. When animals are taken from bank burrows, fill the burrow and the den, itself, with soil so another muskrat won't move in.

Beavers can also have a major influence on wetland areas. During warm seasons beavers feed on aquatic plants but switch to a diet of bark during the fall and winter.

Known for their engineering ability, beavers create their own impoundments with dams made of sticks and mud. They also create channeled runways to allow them access to shallow areas. Beaver activities can complement managed wetlands; their impoundments create attractive waterfowl habitat.

As was the case with muskrats, too many beavers or beavers in the wrong areas can cause problems. Permanent flooding from beaver dams can destroy valuable trees. Extensive bank burrowing may cause problems similar to those caused by muskrats, except on a larger scale. The animals might also block drainage and water-control structures, which would interfere with agricultural activities.

Beavers can be controlled by trapping, but, unlike the muskrat, beaver reproductive capacities are not extremely high and precautions are necessary to prevent elimination of a colony. Limiting the catch is one way to ensure the beaver's continued presence. A previously untrapped colony led by a mature three-year-old, can normally tolerate an annual harvest of three or four animals each year without jeopardizing the future of the colony. Beaver colonies are not permanent. When food resources dwindle, the animals will move to a new site. An advantage to limited trapping in beaver colonies, where their activities are beneficial, is that the annual removal of some animals will lengthen the life expectancy of the colony by reducing the rate at which they deplete the available food.

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