New York State Mammal
Beaver (common name)
Castor canadensis (scientific name)
Beavers are semi-aquatic rodents—the largest rodents in North America and the third largest in the world. These animals are best known for building dams, which they use to create enclosed areas where they can build their lodges. They carry stones and other heavy or cumbersome materials to their building sites, and as a result have become a symbol of hard work and industrious behavior. Their work often helps control erosion and facilitates a stream or river’s natural flow. The beaver has been the New York state animal since 1975. It also appears on the seal of the City of New York, first adopted in the 1600s, in recognition of the important role it played in the city’s economy during the colonial period. The beaver was named the Oregon state animal by the 1969 state legislature.
ALSO KNOWN AS
American beaver, Canadian beaver, flat-tail, bank beaver, castor, castor cat
A beaver is a stocky, large-boned animal with a dark brown, two-layer, oily pelt, and an insulating layer of fat under its skin, adapted for swimming and carrying rather than for moving well on land. Its front legs are shorter than its back legs. Its body is widest at the hips, and narrows gradually toward the nose, similar to a seal or other swimming animal. A beaver has small, round ears high in the rear of its head, and little eyes positioned about halfway between its skull’s base and its nose. It also has an extra transparent eyelid called a nictitating membrane, which allows it to see well underwater. A beaver can also seal its nose and ears when it dives.
A beaver’s most distinctive feature, however, is its flat, paddle-shaped tail, which is mostly covered with dark, leathery scales rather than fur, though a beaver tail may have a few hairs. Beavers’ front feet are short and dexterous with strong claws, adapted for digging and carrying. The animals’ back feet, hairless like their tails, are webbed and adapted for swimming. Males and females are generally about the same size and don’t have easily visible characteristics that differentiate them.
Up to 21 years; up to 11 years in the wild
Big lakes and reservoirs that have irregular shorelines or small streams, ponds, and lakes where beavers can control the quantity and depth of water in which they live.
Range: Throughout the U.S. and Canada and into some areas of Mexico.
Conservation status: Least Concern (LC)
Beavers are usually monogamous, with a couple and their children living together in a lodge. Though males occasionally breed with other females and it’s possible that a beaver may spontaneously relocate and change partners, usually they remain together until one of them dies. In most of the U.S., breeding season is between January and March, but it’s shorter and later in colder climates. A litter can include as many as nine kits, though it’s far more common for a litter size to include about four.
Kits are usually born in spring, learn to swim when they are a week old, and are weaned when they are 2 to 3 months old. Young beavers are mature when they are 2 to 3 years old, at which time the leave their parents’ lodge and search for a new home. Young beavers usually move 5 to 10 miles (8–16 km) away, though they have been known to travel as far as 147 miles (236 km). Beavers are generally more comfortable in water and are graceful if slow swimmers. On land, they usually waddle slowly, though they can lope toward water when frightened.
Top water speed recorded: up to 2 mph (3.2 kph)
Plant matter, especially duck-potato, duckweed, pondweed, water weed, and water lily rhizomes. In winter, beavers may turn to trees for food if not enough soft plant matter is available.
Breeding interval: Annual
Birthing period: April–June
Average litter size: 2–4 kits
Size at birth: 8–22 oz (0.2–0.6 kg)
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Data Source: U.S. Fish and Wildlife Service
Author: World Trade Press