Beaver

 

Beavers help create important habitat for other Isle Royale animals.

NPS

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.

Characteristics

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.

 

Breeding Behavior

•   Reach breeding age at 2 years old.
•   Mate in winter months.
•   Give birth in late spring to litter of 7-9 kits. 
•   Kits can swim as early as one week old.
•   Kits stay close to the lodge for the first few months of life. 
•   Once a young male kit reaches sexual maturity, it leaves its parent’s colony and searches for its own territory. 
•   Young male will start constructing its own dam and beaver lodge to entice a female and start own colony. 
 

 

A beaver colony can be easily spotted by the presence of a beaver lodge.

NPS

Population

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.

 

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  Mammals

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

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  Otter

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

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  Wolves

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