Beaver

• The search for the beaver and its valuable pelt contributed to the exploration and settlement of North America. By the 1830s, after more than 100 years of heavy trapping, the beaver was nearly extinct. Thanks to careful management and control, the beaver began to reappear in the 1930s. Today, beavers are again thriving on many of the waterways of the United States and Canada.
• The beaver is the largest North American rodent. It is the second largest rodent in the world (the capybara of South America is larger). Other than man, the beaver is the only mammal capable of altering its environment to suit its needs.
• Beavers are well-adapted to aquatic life. The nostrils and ears close as the beaver dives and swims. The hind feet are webbed, and the tail is rudderlike. The absence of webbing on the forepaws greatly enhances this animal's engineering abilities.
• Beavers are usually found in headwater areas on small, low streams where underbrush and softwood trees are abundant and close by. With cuttings from these plants, beavers ingeniously construct dams measuring up to 200 feet long and 3 to 4 feet high. One beaver dam was recorded at 1,200 feet long and 3½ feet high!
• Usually, the adult male beaver maintains the dam. If damage to a dam is extensive, other beavers from the family or the colony help out. A beaver population must have a constant water level behind the dam for easy access to food supplies and for protection from land predators.
• Beaver dams provide outdoor recreational benefits. The ponds behind them make good habitat for ducks, song birds, fish, and other wildlife.
• The beaver's home is called a lodge. The lodge is a large pile of brush, sticks, small saplings, and mud with two or more underwater entrances. The lodge usually measures about 20 to 30 feet wide and 4 to 8 feet high, with walls 2 to 3 feet thick.
• Beavers also live in bank dens along streams. These dens usually have only one underwater entrance.
• Beavers use water channels, plus bank slides, to haul plant cuttings to their pond. These cuttings are stored in food piles on the pond bottom. Each beaver lodge usually has two or more food piles to provide the family with food during periods of winter icing. Water channels also are used to move materials for dam and lodge construction.
• Few beavers die from one year to the next. This low turnover in population is due in part to the scarcity of natural enemies and in part to the beaver's ability to make significant changes in its environment.

Beaver Facts

• Mating: monogamous, with mating in February.
• Breeding period: varies by region.
• Gestation period: 90 to 128 days.
• Birth period: April to July.
• Litters per year: 1.
• Number of young: 1 to 8 per litter; usually 4.
• Adult weight: 35 to 70 pounds.
• Life expectancy: 9 to 11 years; some known to reach 20 years.
• Feeding time: mainly at night, but occasionally during daylight hours in remote areas.
• Movement: seldom go more than 50 to 100 yards from the water for food; known to relocate several miles from first lodge as food supply becomes scarce.
• Typical foods: bark and twigs of softwood trees such as poplar, birch, willow, maple, alder; herbaceous plants such as eelgrass, duckweed, waterweed, arrowhead, cattail, sedge, bulrush, goldenrod, water lily roots.