Did you know that the beavers are North America’s largest rodent and second largest rodent worldwide? I guess I never stopped to think about them being in the rodent family because most rodents that come to my mind don’t swim.

During colonial times Beavers were important in the fur trade and contributed significantly to the westward settlement and development of North America and Canada. Nearly extirpated by 1900 through excessive trapping for their fur, their population has rebounded naturally or by human reintroduction.

Beavers have short legs and a stout body with a small, broad, and blunt head. They are approximately 3 feet long and can weigh between 40-60 pounds.

Their incisor teeth have orange outer enamel because iron has replaced calcium, and this makes them stronger than most rodent incisors.

When they are underwater folds of skin close the nostrils, their ears have a membrane to keep water out, and the eyes are protected by a membrane called a nictitating membrane. They are able to close their mouths behind the incisors, blocking water from the mouth and lungs and allowing them to cut, peel, and carry branches underwater.

They have small front feet with five toes that can manipulate food and mud. The hind feet are large, and the five back toes are connected by webbing, which makes them useful as paddles for swimming. Claws of the second hind digits are split and have serrated edges used for grooming the fur.

Their fur allows them to live quite comfortably in the water. The short, fine underfur is densely packed together and keeps the water from reaching their skin. Over this layer is the glossy sleek coat. From tan to chocolate brown to reddish black the glossy fur known as the guard hairs or fur.

Both sexes possess glands that exude a musky secretion, which is deposited on mud or rocks to mark territorial boundaries. Anal glands secrete oil through skin pores that is spread with the front feet and grooming claws over the whole body to keep the fur sleek, oily, and water-repellent.

Beavers are colonial and nocturnal. Their dams are built of branches plastered with mud.

In marshes, lakes, and small rivers, beavers may instead use the banks to construct a dam. They will scrape away the soils from the bank creating an underwater entrance under the tree roots.

Each dam will have an extended family and this family may have an adult pair, young of the year (kits), and yearlings from the previous litter.

Beavers are monogamous, mating between January and March. One litter per year of four kits is born in the spring. Kits are born with their eyes open, teeth present and fully furred.

If some sort of emergency arose, they would be able to swim from the dam.

The distinctive tail is scaly, flat, and paddle-shaped and measures up to 45 cm or about 18 inches long and 5 inches wide. It serves many purposes. They use it to brace themselves when feeding, they are used as rudders to help them swim, when alarmed on land, they retreat to water and warn others by slapping the surface of the water with their tails, producing a loud, startling noise.

Dams are roughly 10 feet high and 20 feet wide the base but can be as large as 16 feet high and 39 feet wide. Tunnel entrances open below the water’s surface and lead into a chamber above water level; the floor is covered with vegetation.

An entry tunnel leads to the nest chamber above the waterline. In winter the moist walls freeze, adding insulation and making the lodge impenetrable to predators such as eagles, hawks, and coyotes.

While they do not need to have the fat reserves like hibernating animals do a small fat reserve is stored in their tails. They are active all winter long and maintain body temperature by huddling together in the dam and being less active. They leave the lodge only to feed on branches stored beneath the ice.

Beavers can remain submerged for up to 15 minutes and swim with the webbed hind feet while the front feet are held tight against the body. On land they walk or run with a waddling gait.

Their diet consists of the soft layer beneath bark, as well as the buds, leaves, and twigs. Pond vegetation and bankside plants are mostly eaten during summer and woody matter during winter.

Some say that beavers are troublesome as they disrupt and alter the landscape. But can’t that description also be applied to us?

Jeannie Carl is a naturalist at the Carbon County Environmental Education Center in Summit Hill. The center rehabilitates injured animals and educates the public on a variety of wildlife found in the area. For information on the Carbon County Environmental Center, visit www.carboneec.org.