The facts about our water mammal neighbors

A friend volunteering at the Evergreen Nature Center last week asked me about an odd water mammal called a nutria. It seems that a volunteer on the boardwalk has pointed out a muskrat to a group of visitors, and this person came into the center and informed the volunteer on duty that “those animals out there are not muskrats; I grew up in Louisiana, and they are nutria. I have seen enough nutria that I know what they look like.”

Well, I am sure he meant well, but he is nevertheless mistaken, or he saw the first nutria in Colorado, a highly unlikely possibility in this part of the U.S.

Nutria are characterized by having two upper teeth (incisors) in the front of their upper jaw and two in their lower jaw. These are the teeth made famous by Bugs Bunny of cartoon fame, although the rabbits and pikas are no longer considered to be true rodents. They are now in an order of their own, Leporidae.

There are many genera in the families of rodents and probably hundreds of species, for this big order includes all squirrels, moles, rats, mice, porcupines, gophers, beavers, water rats and nutria. Four of the families are often described collectively as “odd water mammals.” These are known as the aplodontia family, beaver family, water rat and muskrat family, and the nutria family. Five species of these water mammals are found in the United States. The aplodontia does not occur in Colorado but is found in a small area of the Pacific Northwest. It is considered to be one of the most primitive living rodents. It looks like a small muskrat but appears to be tailless. It actually has a 1-inch tail that is not seen when the animal is sitting or swimming, and it is therefore often described as a tailless muskrat.

The beaver is the only living species in the beaver family. It is the largest of the “water mammals” and has a tail flattened like a canoe paddle. It is an incredible animal that builds dams, creates wetlands and ponds, and gathers winter plant food that it stores in the bottom of its pond.

The water rat and muskrat belong to different genera in the same family. The Florida water rat is the smallest of these “water mammals.” It builds its large nest among the mangrove roots, in stumps and on open savannas near water. It builds its feeding platforms in the water, where it eats water plants and crayfish. It is found only in Florida.

The muskrat is in the genus of ondorata and looks much like a big water rat. They build their nests in the shallow marshes. The nests are entered from below water level and are round mounds of water plants. Muskrats largely eat water plants but also eat clams, frogs and sometimes fish. They may also dig burrows in which they nest. They are common in water habitats in Colorado.

The nutria is the last of these five “water mammals” and as far as is known has not as yet found its way into Colorado. It is a bit smaller than a beaver but weighs considerably less. It is native to South America and was introduced into this country to become a valuable furbearer.

First introduced into Oregon, the nutria is still found in Washington, Oregon and Northern California but has not increased its range to the extent that it has in the Southeast. Introduced into Louisiana, it now can be found across the Southern states from Florida to New Mexico, with the exception of South Carolina, and as far north as Maryland. So unless it has recently crossed the border from New Mexico, it is not found in Colorado.

As a whole, nutria do not like desert climates but prefer more damp, humid air. Since these animals are very similar in general body shape, they can be difficult to identify. While people usually identify other people by their face, the water mammals are best identified by their size and tail. They are all fascinating creatures that enjoy living in wet habitats and have found many ways of adapting to life in their soggy environment.

The chart above will help to quickly identify animals you see.