Muskrat - (Ondatra zibethicus)
The appropriate common name refers to the mild and inoffensive odor of this rodent. Although superficially ratlike in appearance, the muskrat is not a close relative of the despised house rat.
Description
This medium-sized mammal has short front legs with small feet, stronger hind legs with large feet, and a vertically flattened, scaly tail which is slightly shorter than the combined length of head and body. The hind feet are partially webbed. The back is blackish brown and the sides are lighter brown with a reddish tinge; the underparts are still lighter, shading to white on the throat. Adults are 16-25 1/4 inches (406-641 mm) long and weigh from 1 1/2-4 pounds (680-1,814 g).
Distribution and abundance
The muskrat is widely distributed throughout Alaska, Canada and the United States; as a transplant, it is also established in Europe and Asia. Although it is one of the most abundant, commercial furbearers in Missouri, it never has been as common here as in some other parts of its range.
The construction of thousands of farm ponds throughout the state during the past 40 years has accounted for an appreciable increase in muskrat numbers and distribution.
Habitat and home
Muskrats are semi-aquatic, living in marshes, sloughs, streams, rivers, ponds and lakes. Here they dig homes in a stream or pond bank or build large houses out of vegetation in the shallow water. The nest, or den, is reached by means of a tunnel which usually opens under water.
Habits
In addition to building homes, muskrats often undertake other construction. Platforms for resting and feeding are made of mud and vegetation, and sometimes jetties are built for landing places along marshy shores.
The area an individual occupies depends to a certain extent upon the size and shape of the water area in which it lives. Muskrats living in the center of a marsh usually occupy a circular area, while those living along the shoreline of a marsh or river occupy a narrow area extending from bank burrow out several hundred feet into deep water.
Muskrats readily fight one another, especially during food shortages. The defeated individual must leave; the victorious remains. This is one way the muskrat population of an area is kept within the limits of the food supply.
Foods
In the marshy areas of Missouri,muskrats eat rootstocks and stems of cattail and three-square bulrush, and the seeds of lotus. In other areas of the state, white clover, corn and bluegrass are preferred foods. Muskrats living along Ozark streams feed upon freshwater clams, snails, crayfish, fish, frogs and aquatic plants.
Reproduction
The breeding season in Missouri begins in late winter and extends to the middle of September. Three peaks of mating occur: the last of March, the last of April and the last of May. Pregnancy averages 28 days. From one to five litters may be produced annually by a female, but two or three are the most common. The litters usually contain between four and seven young.
At birth the young are blind, nearly helpless and practically naked. By 1 week of age they are covered with coarse gray-brown fur. The eyes open between 14 and 16 days of age. About this time, the young can swim and dive and climb on low, floating objects. Weaning occurs between 3 and 4 weeks of age. It is possible for young born in early spring to breed in late summer, but most breed for the first time in the spring following their birth.
Importance
Muskrat pelts are one of the most common furs on the commercial market, and almost the entire crop is used in the manufacture of women's coats. Muskrat fur is durable; the skin makes strong leather and takes dye well. The flesh has a gamey flavor. Dried musk is used in the manufacture of perfumes and in preparing scent for trapping animals.
Management
In Missouri, the most important management measure is to regulate the harvest. Where muskrats are too numerous, trapping is the most satisfactory means of control.
There is no practical way to keep muskrats out of ponds, but ponds can be constructed to minimize damage to dams by the burrowing rats. Recommended measures include having the freeboard of the dam at least three feet high to allow ample room for denning and to prevent the den from being built too near the surface of the ground; having the spillway of sufficient width and slope to prevent flooding of the den and subsequent digging of new dens; and fencing the pond to exclude livestock that trample the dam and banks, causing cave-ins of muskrat tunnel systems and thereby starting erosion. Asbestos-cement sheets placed vertically within a dam or dike prove an effective barrier to muskrat burrowing both in new dams or dikes and in those already damaged by burrows.
