North American Beaver

Castor canadensis

Physical Characteristics

North American Beavers are smaller than their European cousins but look very similar. Each have short faces with large incisors meant for chewing and cutting wood. The teeth appear orange-yellow in color, because the thick enamel contains iron deposits which keep the enamel strong. Because the teeth have hard enamel up front and softer material called dentin in the back, this rodent’s teeth are self-sharpening! Beavers use these teeth to cut down trees and shrubs to build their dams and lodges.

Beavers have long flat tails which can serve a variety of purposes. The tail contains fat deposits which the beaver can use as energy during times when food is scarce. It can be used as a seat while at rest and a rudder while swimming. When a beaver feels threatened it will slap its tail on the surface of the water, warning other beavers in the area that trouble is approaching!

Beavers are a semi-aquatic mammal, which means they spend a lot of time in water. To help them in the water, beavers have webbed feet and can produce an oil to spread all over their fur. The oily fur creates a buffer between the beaver’s skin and the cold water so the they can stay warm. Beavers produce a chemical called castoreum from their scent glands which they use to mark. Castoreum has been used medicinally for centuries and is one of the reasons beaver populations plummeted after human colonization.


Beavers are known for damming up rivers and creating large wetlands and lakes where they build their lodges. When they find a suitable stream or river they will begin cutting down large trees and placing them vertically in the bed of the river. When they have a solid foundation, they will then start placing logs horizontally across the beams until they dam up the river. When the water backs up along the stream it can create a lake or wetland which the beaver can use to build a lodge. Lodges are the beaver’s home; they use them as shelter, a den for rearing pups, and even as a source of food in the winter! While they are building their lodge, beavers use enough mud to completely insulate them against the cold in the winter. Their body heat is enough to warm the small living space inside the lodge and the hard mud insulating them even serves as protection from predators. Predators like coyotes and wolves are no match for the ingenuity of a beaver!

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Written by Rob Nelson

Rob is an ecologist from the University of Hawaii. He is the co-creator and director of Untamed Science. His goal is to create videos and content that are entertaining, accurate, and educational. When he's not making science content, he races whitewater kayaks and works on Stone Age Man.

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