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| An adult Beaver weighs from 16 to 32 kg and, including its 30-cm tail, may measure as long as 1.3 metres. It is the largest rodent in North America and largest in the world except for the Capybara of South America. They have long, self-sharpening, strong incisors that grow continuously. Their lips can be closed behind the incisors, permitting the Beaver to gnaw on twigs while under water. Its tail serves as a fat storage depot in the colder months, as a radiator for releasing excess heat in warm weather, and as a rudder while swimming. On land, the tail assists in balance for sitting or standing upright. It also serves as a counterbalance and support when the animal is walking on its hind legs while carrying building materials like mud, stones, or branches with its front paws. The Beaver will dive after being frightened and slap the water with its tail, making a noise like a pistol shot, which warns other Beavers in the area that danger is near. The Beaver is a strong swimmer, both under water and on the surface, and can achieve speeds up to 7 km per hour if alarmed. It has webbed hind feet, oil glands at the base of the tail for waterproofing the Beaver's fur, a split toenail on each hind foot which serves as a comb, ear valves which close when the Beaver dives, and castor glands as a source of sweet-smelling perfume used to mark their ponds so any transient Beavers know that the pond is occupied. A Beaver colony typically consists of two mated adults, that year’s litter, averaging three or four kits that are born in May or June, and sometimes the young from the year before. Their prosperity is dependant upon the availability of high quality food. The young stay with their parents until they are two and sometimes three years old. Beavers fell trees to obtain leaves, buds and bark for food, and for woody branches used in the construction of their dams and lodges. They prefer Trembling Aspen, Poplar, Willow, and Birch. They use their front paws to plaster mud on dams and lodges. A dam is only built when there is a need to enlarge the underwater habitat that will be open to them in winter, thereby creating a pond deep enough that it will not freeze to the bottom. Deep water provides storage for winter food and a year-round underwater access to their lodge or den secure from predators. Although their aquatic habitat offers excellent protection from predators, Beavers often fall prey to Wolves, Bears, and Bobcats when foraging on shore or migrating overland. The Otter is able to enter the den via the water and kill the kits inside; however, an adult or sub-adult Beaver always stays with the kit to offer protection. Sudden fluctuations in water levels can force Beavers to leave their den and face danger on shore. |
(Family Castoridae)
American Beaver (Castor canadensis)
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