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Region: North America Class: Mammalia Order: Rodentia Family: Castoridae Genus: Castor Scientific Name: Castor canadensis
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Description:
The largest rodent in North America and second in size only to the Capybara. High-rumped, short eared, five toes on all feet, only hind feet webbed. Second toes on hind feet have a double claw used for grooming. The two incisors in each jaw grow continuously as they are worn away. Four rootless molars with crescent ridges of hard enamel on the crowns are used for cutting the fibres of their wood diet.
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Distribution:
The whole of North America except the extreme North of Canada, the deserts of south western USA, Mexico and Florida.
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Habitat:
Almost entirely aquatic. Lives in colonies of family groups in burrows, stream banks or in lodges of mud, stones and tree branches. Access to both burrows and lodges is sub-surface for protection from predators. Lodges are usually 2.5 to 3.5 m in diameter by 1 m high, but may be as large as 5 m by 2 m high.
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Food:
Exclusively herbivorous. The bark of hardwood trees such as poplar, aspen, birch, cherry, willow, maple and alder.
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Reproduction and Development:
Usually monogamous, but when one mate dies the other will mate again. Family groups consists of two adults, several two year olds and the young of the current year. They mate at about 3 years of age. Gestation is 100 - 110 days and usually 2 - 4 young are born. Kits can swim a few hours after birth and are weaned at one month. Young leave or are forced out of the colony by the age of two. Large lodges may have several family groups. Family life is co-operative, all help with food gathering and building. Their life span is 35- 50 years in captivity.
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Adaptations:
Swim very efficiently using hind feet and tail. Valves in nose and throat close automatically when submerging, allowing them to stay under water for up to 15 minutes. The mouth closes behind the incisors allowing them to carry sticks in their mouth while swimming. They eyes have membranes which can be drawn over the eyeball. Their blood supply can be diverted from the paws to ensure supply to the brain and their metabolism can slow down to conserve blood supply. Both males and females have sex glands which exude oily musk (castoreum) which is used for trail marking, to attract others and to waterproof fur.
The beaver’s large incisors have hard enamel faces and softer dentine backs. The dentine wears away faster than the enamel as the animal gnaws, leaving a keen biting edge of enamel at all times. These incisors never stop growing, so the beaver has to chew or grind its teeth continually to keep them ground down to a manageable length. If a beaver breaks a tooth or otherwise distorts its bite, the incisors elongate, force open the mouth permanently and cause the animal to starve.
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Threats to Survival:
Destruction of habitat, water pollution, silting of streams and loss of food resulting from forestry and hydroelectric operations are problems for beavers. The young are threatened by bears, wolves, wolverines, lynx and otter.
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Status:
Common
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Zoo Diet:
Ruminant cubes, yams, poplar and willow browse.
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Store
Animal Fact Sheet
The New Tundra Trek