Beavers

Beavers, Castor canadensis, members of the order Rodentia, are mammals characterized by a single pair of continuously growing teeth located in each of the upper and lower jaws.  Between three and three-and-a-half feet in length, beavers weigh 26 to 60 pounds.  Their fur is reddish-brown with an outer layer of long, coarse guard hairs covering an inner layer of fine, short hair.  Beavers often groom themselves and comb oil into their fur to make it waterproof, keeping the animal dry and warm.  Their tails are covered with leathery scales and a few short hairs.

A beaver’s body, shaped like a bullet, is made for swimming with a top speed of 6-mph in the water.  Their  back feet have five toes with flexible webbing in between providing lots of power in the water, but making them rather clumsy and slow on land.  Several other adaptations assist in making a beaver an incredible swimmer. Valves in their ears and nose can be closed to prevent water from entering.  The eyes have a transparent eyelid that closes, protecting the eye, but allows them to still see underwater.   Beavers can remain underwater for up to 15 minutes, covering a half-mile in distance.  Upon diving, the heart rate slows by half, and the animal can tolerate a considerable amount of carbon dioxide buildup before requiring clean oxygen.  They keep their front paws balled up in fists close to their heads to act as bumpers to push floating debris away, and their tail acts as a rudder.

Beavers live in colonies including a male and female who mate for life, their yearlings and new born kits.  Kits mature in one-and-a-half to two years, and are then encouraged to move out on their own.  Evidence of beaver activity in an area includes dams, gnawed trunks, paths and mudslides.  Beavers make paths about a foot wide with trimmed edges and a brushed surface leading from their dwelling to feeding grounds.  As paths become well used, they turn into mudslides when they lead into a pond.  Usually roaming no more than a half mile from home, families will leave scent mounds of mud and bark mixed with anal gland secretions to mark their territories.  When swimming, tails are used to send a warning by slapping the water.  This not only creates a loud sound, but also can be used to generate a wave of water in the face of a potential predator allowing the beaver time to escape.

Beavers are herbivores, and the plants they eat depend on what species are available in their home habitat.  Woody species are an important food source during winter months, and are harvested in summer and fall to be cached in their dwelling or at the bottom of ponds near the dwelling entrance.  These can then be accessed during winter months even if ponds are frozen over.  Beavers are known to eat willow, river birch, maple, cottonwood, black cherry, dogwood, beech, and oak.  They also eat roots and rhizomes of aquatic plants including water lilies, duckweed, arrowhead, and cattails, and will consume grasses, sedges, clovers, and corn on land.  Beavers eat one-and-a-half to two pounds of food daily.

In the mid-to-late 1800s, beavers were extirpated in many localities by trapping for the fur trading industry.  Reintroduced from neighboring colonies throughout the first half of the 1900s, beavers continue to fill an important role in the proper functioning of an ecosystem from blocking flowing water to create new wetlands to removing stands of trees and allowing new vegetation to colonize an area.  New wetlands attract waterfowl, turtles, snakes, mammals, and insects.  After several generations have cleared the surrounding land of trees and shrubs, beavers will move to a new area, allowing the abandoned homesite to slowly drain and fill in with new soils and opportunities for meadow flora and fauna.