American Beaver

ZOO LOCATION: The Loft (Outside, south end)

Lifespan: Up to 20 years

Wild Diet: Mostly tree bark, cambium (soft tissue growing under the bark); Also eats roots, buds and water plants

Zoo Diet: Yams, lettuce, carrots, moose chow and rodent chow.

Predators: Mink eat some kits, and coyotes capture beaver on dry land.


IUCN Status: Least Concern

Habitat/Range: Rivers, streams, ponds, small lakes and marshes in North America, part of Canada and northern Mexico

Characteristics: Second largest rodent in the world after capybara and North America's largest rodent. Adults can be up to 4 ft. long and weigh over 60 lbs. Growing throughout their lives, females are as large as or larger than males of the same age. Built for aquatic life, they have webbed hind feet and a large, broad, flat, nearly hairless tail. Their tails are covered with large, black scales to help maintain balance when gnawing on trees and as a rudder when swimming. Short front legs have heavy claws for digging and their rear legs are longer. When underwater, nose and ears close up and nictitating membranes cover eyes. Coat consists of fine under hairs and longer, more coarse guard hairs. Beavers have dark brown fur on back and sides and lighter brown fur on their chest and belly. Thick layer of fat under their skin helps keep them warm. Long, sharp upper/ lower incisors are used to cut into trees and woody vegetation. Incisors grow throughout life.

Behavior: Beavers live in family groups or colonies. A colony is made up of a breeding male, female and their offspring. Known for building dams of mud, brush, stones, poles, vegetation in rivers and streams, and building homes (beaver lodges) in the eventual pond. Beaver dams are created both as a protection against predators and to provide easy access to food during winter. They can rebuild a destroyed dam overnight. Beavers dig out the den with an underwater entrance after finishing the dam and lodge structure. There are typically two dens within lodge, one for drying off after exiting the water, another where family lives. The floor is usually a bit above the water and covered in woodchips to absorb moisture. A vent in the lodge lets in fresh air. Not all beavers build lodges, some build burrows in the banks of rivers. Very territorial, beavers will protect lodges from other beavers. They mark their territory by building piles of mud and scent marking it. Beavers slap their tail against the water to signal danger or to warn away predators. That slap can be heard over large distances above and below water. Beavers also communicate with postures, scent marking and vocalizations. Incredible swimmers, beavers can swim up to 6 miles an hour and stay submerged for up to 15 minutes.

Reproduction: Beavers mate for life and are considered mature at three years old. Mating season occurs January and March in cold regions; late November or December in the south. Gestation lasts about 90 days. Females have one litter of kits a year, up to 8, usually 2-4. Beaver kits are well furred and eyes open when born. They can swim within 24 hours of birth and exploring outside with parents within a few days. If tired, kits may rest or be ferried upon the mother's back. On land, mother often carries kits on her broad tail and sometimes walks erect holding them in her forepaws. Young are weaned in about two weeks but stay with parents for 2 years. Both parents participate in the care of young.

Conservation: Beavers are abundant today, and it's often hard to believe that they were once near extinction due to the demand from the fur trade. The modifications they make to their environment often conflicts with human habits. In Colorado, beaver are protected except for those causing damage to agricultural land and property one 30-day period a year. Since trapping is not an option, nor a long term solution, people need to learn to live responsibly with beavers and other wildlife.