Muskrat (Ondatra zibethicus)
Class: Mammalia
Order: Rodentia
Family: Arvicolidae

Muskrats are widespread across the northern Hemisphere. They are native to Canada and the USA and feral in Europe.

Muskrats are water mammals measuring about 25-35cm body + 19-27 cm tail. The weight is 600-1800 gr. They have long rusty brown hairs with very dense silky under fur. In fact they have the most hairs per square inch of all living mammals. The belly side is lighter colored. They have a sideways flattened tail and long web like hairs on their hind feet.

Muskrats can stay under water for almost 15 minutes without taking a breath. Muskrats got small ears which can be closed under water. They are able to gnaw under water because their lips can be sealed behind their yellow incisor teeth.

One pair of muskrats will raise 1- 4 litters of 4-8 young in one year. When the first litter is born early these animals will have a litter themselves in the same year. In Europe muskrats tend to get more and bigger litters than in the USA.

Habitat and habits

Muskrats are not very choosy in where they live. Any stream, channel or pond will do as long as water and food is present. Muskrats are mainly herbivores but will occasionally feed on crayfish and shells too. Their main diet consists of water plants reeds grass and roots of water plants. They will eat their food in their dens most of the time. Especially in the time they got their young, big mouths full of plants will be taken to the den.

Where they can muskrats will dig holes in a bank. The entrance is always under water to seal of the muskrats odor. This will prevent other animals that prey on muskrats from finding the den. Mink and otter prey on muskrats and young muskrats can be eaten by herons and muskies. Especially in the time when the young are reared muskrats will close any air hole in the bank with balls of water plants. When there are no banks available ore when the banks are too shallow the muskrats will build huge piles of reeds in which they will build their nest. These reed nests can be up to 2 meters high. Like the dens in a bank the entrance is also under water.

In spring muskrats mate and find a spot were they will spend the summer and rear their young. Muskrats are territorial and don’t accept other pairs in their territory. The den will be expanded every time a litter of young is born and raised. In autumn the families will split up and find a place to stay in winter. This is called the autumn migration. In winter muskrats will feed under the ice with reed roots. After the wintertime when the ice is melting spring migration sets in. The muskrats hurry to their breeding grounds to find a territory.

In Europe where muskrats are considered a feral pest these migrations are used in lethal controlling. It seems that the migration movement in Europe is stronger than in the USA.

Nuisance

Muskrats can cause problems because of their habit to dig their dens in banks and dikes. One muskrat will dig out 1 cubic meter of soil in one year. This constant digging can pose a threat to the strength of the dike. Muskrats can also ruin water plants in ponds by eating them or by digging out roots. In artificial ponds and swimming pools muskrats can gnaw holes in the liner and cause damage by doing so. In such cases lethal control can be necessary.

Written in friendship for David McDaniel

Eddie van Marum 03-01-2005
Eddie Van Marum is a professional muskrat controller for the province Groningen in Holland