Beaver sitting on the ground surrounded by colored leaves.
Beavers help create important habitat for other Isle Royale animals.


Nature's Engineer

The American Beaver (Castor canadensis) is known as nature’s engineer due to their ability to alter their environment to create a suitable habitat to raise young. They alter the environment by:

  • Building a dam upon a water source.
  • An intricate lodge is constructed of sticks and mud as the pond fills up.
  • The lone entrance to the lodge is underwater, which protects against predators.

Isle Royale is home to hundreds of beaver ponds which provide excellent habitat for moose, water birds, and an array of aquatic species.


The beaver is the largest rodent in North America, weighing between 33-55 pounds, and has distinct large, orange incisors that keep growing throughout its life. These teeth are kept short by gnawing on wood and cutting down trees. Their fur coat is dark brown and consists of two layers keep the beaver warm and dry. Their scaly, paddle-like tail serves many purposes: a rudder when swimming, a kick-stand to balance themselves standing on the back feet, a warning to intruders when slapped against the water, fat storage, and sweat glands.

A beaver hut, constructed of mud and sticks, sitting in a beaver pond.
A beaver colony can be easily spotted by the presence of a beaver lodge.



Autumn is the season when the beaver count occurs on Isle Royale. The lack of snow cover, and the trees being devoid of leaves, allows flyovers of the island to count active beaver colonies. In autumn of 2018, researchers counted a total 542 active colonies. These colonies reside primarily on the island’s streams and rivers. However, some do live on in-land lakes and even the Lake Superior shoreline. Including the parents and kits, each colony could have up to 10 to 12 family members residing there. An estimated 5,500 to 5,600 individual beavers were living on Isle Royale during the time of the autumn 2018 count.


Eager to See a Beaver?

Beavers are commonly seen:

  • Swimming along the shorelines of interior lakes and Lake Superior.
  • Near chewed down trees along water edges.
  • Close to beaver lodges that are scattered throughout the park.
    • Active lodges can be identified by recently peeled logs places on top of beaver-lodge with a fresh coating of mud.
  • A red fox lays on the grass sleeping

    The 18 mammal species present on the island must cross Lake Superior.

  • Two Northern River Otters swim in Lake Superior.

    River otters are among the best swimmers in the weasel family.

  • Wolf on the prowl through a snowy forest

    Wolves have been the apex predator on Isle Royale since 1948.

Last updated: December 9, 2020

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