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Blane Klemek column: Muskrats have unique adaptations

The two summers I spent wading in wetlands throughout North Dakota's prairie potholes were two of the most interesting and rewarding summers of my life.

The work, if one could call it work, was my graduate research project, which was the primary requirement for earning my master's degree. I spent countless hours all alone surveying wetland birds and wetland plants day in and day out for weeks at a time.

Aside from the myriad species of plants and birds that I became intimately acquainted with over the course of those glorious summer months, I also got to know other fascinating creatures. Indeed, such insects as whirly-gig beetles, water striders and dragonflies were always entertaining diversions from collecting my field data.

As well, there were amphibians, namely leopard frogs and tiger salamander larvae. Sometimes I observed small groups of American white pelicans literally herd salamander larvae into shallow areas of wetlands and gorge themselves on the swimming lizard-like amphibians. The giant birds would later fly to their nesting colony at nearby Chase Lake National Wildlife Refuge where they would regurgitate the salamanders for their hungry and fast-growing chicks.

Another of the many species of wildlife that I commonly observed was an aquatic mammal, the muskrat, which I came to consider as a sort of curious furry friend that I would encounter almost daily during the course of my research work. The animals rarely paid any attention to me, even though I would frequently stop and observe each and every one of them for a moment or two. I was continually fascinated by their quiet and purposeful nature.

Some muskrats were inquisitive little fellows that swam uncomfortably close to me. One memorable muskrat upon noticing me standing near a thick wall of cattails next to a pocket of open water in the middle of a small wetland, turned and swam straight for me. As he neared where I stood, he suddenly dove and struck my left leg. The animal then surfaced a few feet later and disappeared into the cattails. I'm almost positive the muskrat intentionally bumped me.

Distributed across most of North America, muskrats are very common and abundant relatives of squirrels, gophers, mice and voles. In fact, muskrats look very much like overgrown voles. Belonging to the large mammalian order "Rodentia," the muskrat is, of course, a rodent. And, like all rodents, muskrats have two pairs of incisors - a pair on the top and a pair on the bottom - that are kept in chisel-like form by their constant gnawing.

Most muskrats are no longer than 20 inches in length, including their 9- or 10-inch long hairless tail. They weigh around two to five pounds. Living only about four or five years, muskrats are, nonetheless, extremely prolific. Populations often become very dense, which in turn cause fierce competition for resources and mass migrations to other areas. As well, outbreaks of diseases and parasites and increased predation by enemies also occur when muskrat populations explode.

To protect themselves from the elements and predators, muskrats usually build lodge-like shelters that consist of vegetation gathered from their surroundings. Muskrats also dig tunnels and dens into the banks of rivers, flooded ditches and dikes. "Bank rats" can be problematic for road authorities and wildlife managers when roadways and dikes are undermined by burrowing muskrats.

Because muskrats often live in the same environments and have similar habits as their larger cousin the beaver, people sometimes mistake the much smaller muskrat for a beaver. Muskrats swim upon the surface of the water, using their hind feet for propulsion and their tails for steering, and can dive and stay underwater for 10 or more minutes without surfacing for air. And similar to beavers, muskrats have folds of skin inside their mouths that close behind their teeth, effectively keeping water out while they cut or dig submerged foods.

Muskrats are interesting denizens of aquatic environments. In the wintertime, they keep their holes through the ice open or semi-open by plugging the holes or cracks with vegetation. Over time, as the muskrat continues to push vegetation up through the hole, a mound forms on top of the ice creating a makeshift feed-house. Such temporary housing (called "push-ups") provides a warm and protected place to feed.

Over the years, I have encountered muskrats in all kinds of different and interesting situations. I've had them swim into my fish house through the ice hole while I was spearing pike. I've watched them forage for various tubers and greens within their wetland haunts. I've observed them cleaning themselves on top of their lodges in the warm sun. And I've had at least one especially bold muskrat give me a not-so-subtle "bump" as a reminder to me that I was standing in its home.

Muskrats, those remarkable Minnesota mammals that inhabit our lakes, rivers, and wetlands, are intriguing furbearers for all of us to observe as we get out and enjoy the great outdoors.

Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at