Beavers: Ecosystem Engineers

If you've ever been out on a hike and see trees that appear to have been chewed all the way around, or heard a loud slapping splash, you know you're in beaver (Castor canadensis) country. Whether you love or despise beavers, there's no questioning the enormous impact they have on the ecosystem.

Beaver pelts were of such value to early fur traders that the species was nearly wiped out in New York State by 1640. Due to reintroduction and protection in the early 20^th century, Beavers have since rebounded, to the dismay of some landowners. Beavers build dams that turn streams into lakes. The trees use to create these dams come from the surrounding woodland, further altering the landscape and ecology. A central cavity above the water line is usually excavated from the dam by the beavers. You can find anywhere from 1-12 beavers in a colony, which is sort of like an extended family. Young are born in the spring. They are sexually mature after 1.5-2 years, and depending on the size of the colony, older offspring will eventually move off to form their own colonies.[1]

Because Beavers are primarily nocturnal, you are more likely to see the signs of their presence or hear the loud warning slap of their tails on the water than you are to see the beavers themselves. The large paddle-like tail aids in swimming as well as communication. Like all rodents, Beavers have constantly growing incisors. Their large jaw muscles aid in chewing trees. Beavers actually eat the inner bark of trees, more so in the winter when there are fewer aquatic plants available. The bark of smaller trees holds higher nutritional value and is usually more edible than the bark of older, larger trees. Cellulose, the main component of plant cells walls, is hard to digest. Beavers have Bacteria and Fungi living in their guts to aid in the breakdown of their woody diets.

Once a beaver colony has cleared the surrounding area of all the useable trees, it will move on to a new area. Some Beaver colonies will build multiple dams over the years. Thus you will often find areas with beaver dams but no indication of current activity. The next time you are in the woods, take a look around and see if you see any Beaver signs! Perhaps that lake hasn't been there forever after all. . . .

[1] Saunders, Andrew. Adirondack Mammals. State University of New York College of Environmental Science and Forestry. 2003