Bumps on the Water: an introduction to the semiaquatic mammals of the Belgrade Lakes

-Written by Logan Parker, MLRC Community Engagement Coordinator

When it comes to wildlife in and on our lakes, it seems the birds and fish get most of the attention. The shelves of many of our watershed’s tourist shops are good evidence of this with their inventory of loon-this and trout-that. While loons are surely majestic and trout are truly a prize catch, there is another class of animal that living in and on the Belgrade Lakes worthy of our fascination: mammals.

While the lakes and surrounding lands support a great diversity of mammals, there exists a group of creatures that have evolved to fit special aquatic niches. These are, of course, the semiaquatic mammals. Notable examples residing in our watershed include the beaver, the mink, the muskrat, and the otter. Each with distinct evolutionary origins, these mammals have developed diverse means of surviving a life spent mostly in freshwater.

American BeaverPerhaps the most well-known member of the bunch is the American beaver (Castor canadensis). The largest rodent in North America, the beaver is easily recognized by its substantial size (35 – 70 lbs), webbed hind feet, and broad, flat, and scaly tail (Reid, 2006). It is famous (or perhaps, infamous) for its ability to fell trees for the purposes of engineering dams and lodges. Given the somewhat static water levels that lakes provide, our resident beaver spend much of their time amassing underwater food stores and constructing the impressive lodges they overwinter within (sometimes inside of boathouses). These animals are active year-round and continue to swim to previously gathered trees and branches below the winter ice (Kricher and Morrison, 1988).

American MinkAn animal I’ve frequently seen bounding along rocky shoreline of Long Pond, the slender American mink (Mustela vison) is stark contrast to the portly beaver. This dark-brown mustelid is an adaptable predator that pursues prey both on land and in the water. “They eat fish, crayfish, rodents, and other small prey”, but have also been observed at times hunting larger prey such as muskrats and ducks. Minks are highly territorial animals and, for that reason, their populations around the lakes remain low (Tobiessen, 2012). During the winter months, these predators move to inland forests to pursue terrestrial prey such as rabbits (Reid, 2006).

Common MuskratLike the beaver, the Common muskrat (Ondatra zibethicus) is a rodent. Despite what their name might imply, however, these animals are not “true rats”. Also like beavers, the muskrat has a scaled tail. Unlike the beaver’s tail, the muskrat’s tail is laterally compressed and is the main means of propulsion in the water (Reid, 2006). These small mammals are voracious eaters of cattails and sedges, but also prey upon amphibians, mussels, and crayfish. Early each winter, we spot muskrats perched on the edge of newly formed ice in Mill stream feeding on aquatic vegetation collected down in the stream-bed below.


River Otter SwimmingA streamlined mammal with long, powerful tail, short ears, and webbed feet, the North American river otter (Lontra canadensis) is truly at home in the water. These accomplished predators are equipped with powerful jaws and sharp canine teeth. Don’t let the predator status fool you, however – these are highly gregarious and playful animals. Adult females lead troops of their progeny that hunt, rest, groom, and play together (Lariviere and Walton, 1998). In winter, these animals travel over land and ice to areas of open water in which to hunt. A great place to watch for river otter on the move is in the outlet of Belgrade stream into Messalonskee Lake as the lake begins to freeze over. To reach their hunting grounds, river otter gallop, bound, and even slide on their long, smooth bellies.

River OtterThese profiles are merely introductions of some of fascinating wildlife that thrives in the Belgrade Lakes watershed. If you have questions or comments about our watershed’s wildlife, give us a call or send us an email. We would be glad to support in your wildlife observations! If you have pictures of interesting wildlife spotted in the watershed, consider sharing them to our Facebook page. We would love to see them!




Kricher, John C., and Gordon Morrison. Eastern Forests: A Field Guide to Birds, Mammals, Trees, Flowers, and More. Boston: Houghton Mifflin, 1988. Print. Peterson Field Guides.

Lariviere, Serge, and Lyle R. Walton. “Lontra Canadensis.” Mammalian Species (1998): 1-8. Print. American Society of Mammalogists.

Reid, Fiona A. Mammals of North America. 4th ed. Boston: Houghton Mifflin, 2006. Print. Peterson Field Guide.

Tobiessen, Peter. The Secret Life of a Lake: The Ecology of Northern Lakes and Their Stewardship. Niskayuna, NY: Graphite, 2012. Print.