Muskrat

Ondatra zibethicus cinnamominus (Hollister)

 

 

Description:   The muskrat is the largest of the microtine rodents and has several aquatic adaptations. It can be distinguished from other members of its family by: 1) dense waterproof fur, 2) laterally compressed, scaly tail, 3) large, partly webbed hind feet, 4) heavy-set body, 5) relatively large head with small ears and eyes, 6) blackish brown upperparts (darker on the head) with long black guard hairs which give a glossy effect, 7) paler sides with a yellowish tinge and fewer guard hairs, and 8) silvery gray underparts with a white throat. Summer pelage is paler than winter pelage, and young are grayer than adults. Musk glands in both sexes are located at the base of the tail. Females have 8-10 nipples, and the presence or absence of these nipples is the easiest way to differentiate males from females, since the sexes are otherwise alike externally.

Size:   Adults may attain the following dimensions: total length 470-578 mm: tail 200-260 mm; hind foot 65-81 mm; ear 20-25 m; weight 725-1550 grams.

Range and Habitat:   Muskrats are found throughout Kansas. They are semi-aquatic and is always associated with water, including marshes, lakes, ponds, slow-moving rivers, creeks, ditches, and other waterways.

Reproduction:   Muskrats are prolific, producing two or three litters per year of from two to nine (usually six) young per litter after a gestation period of 29 to 31 days. The eyes of newborn muskrats are closed and their bodies are hairless. In one week hair appears, and in 14 days their eyes open and they are capable of swimming and feeding. In three or four weeks they are weaned. In six months they attain the size of adults, and in a year or less reach sexual maturity.

Habits:   The muskrat is a good swimmer and is most frequently seen in the water with its head partly above and body submerged, or feeding on a beach or bank at river edge. Tracks with tail marks may be found in mud or sand along the edge of the water. Muskrats are mainly nocturnal, but may be active during the day if not disturbed. Muskrat dens are conspicuous conical piles of damp vegetation that rest on the bottom of a lake or pond in shallow water. They are from one third to one meter high, and contain a central nest cavity lined with fine grasses. In summer one muskrat family occupies a single nest and defends the territory surrounding it. In winter more vegetation and mud is added to the den for insulation and several families may occupy the same house. Bank dens are also excavated at water level with access directly from deep water. Dens farther inland may be connected by a shallow canal across the intervening beach or mud flat, and receding water in a lake may necessitate extending the canal system. Shallow water or marshy ground between two bodies of water will certainly have a muskrat trail or canal connecting them. Flat platforms of vegetation may be used for resting or feeding, as well as a place to deposit fecal droppings. Logs, rock, and elevated sites along the edge of water are also used as scent posts. Muskrats are frequently associated with beavers with which they co-exist amicably. Like beavers they can remain underwater for fifteen or more minutes.

Food:   Food of muskrats includes a variety of aquatic plants including roots, bulbs, and stems as well as considerable animal material, favorites being clams, snails, fish, and crayfish.

Remarks:   Hawks, owls, foxes, coyotes, turtles, and large fish are potential predators of the muskrat, but mink are especially serious predators. Life span of muskrats is three to four years or less, but they have potential longevity of seven or eight years.


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