The beaver is a large semiaquatic rodent. There are two species of beaver, the North American beaver (Castor canadensis) which is native to North America, and the Eurasian beaver (Castor fiber) which is native to Eurasia. These animals are thus found in three continents namely; Europe, Asia, and North America. Beavers are the second largest rodents in the world and are known for building lodges, canals, and dams across waterways. The deep waters of the dams are used to protect the colonies from predators as well as move food and building material.
Physical Characteristics of Beavers
Beavers measure around 31 inches in length and weigh between 35-66 pounds. Beavers have a stout body, short legs, and a small blunt head. The hind feet are webbed which enable the beavers to swim with ease. Beavers also have chiseled-shaped incisors that have orange outer enamel containing iron which makes them strong and resistant to acid unlike the enamel in the teeth of other animals. The beaver has dense brown or grayish fur and a distinctive tail which measures about 18 inches long and 5 inches wide. The tail is flat, scaly and paddle-shaped and is adapted to suit the amphibious nature of the rodent as well as for storage of fat during winter. Beavers are primarily nocturnal and typically feed on buds, leaves, twigs, pond vegetation and the cambium layer beneath the bark.
Habitat and Behavior
Beavers build their homes in rivers, streams, marshes, ponds, and lake shorelines. Beavers are often referred to as ecological engineers due to their ability to alter the landscape they live in by building dams spanning many hectares from mud, stone, and branches. They live in distinctive dome-shaped island lodges or bank lodges in small rivers marshes and lakes. In large rivers, beavers excavate bank dens that have underwater entrances beneath the roots of trees. Beavers built dams a short distance away from their lodges to increase the depth of the water around the lodges and to deter predators. Lodges are usually 10 feet high and 20 feet across the base with some being as large as 16 feet high and 39 feet wide. Each lodge is home to an extended family of about eight beavers. The extended family consists of an adult breeding pair, offspring of the year usually known as kits and yearlings of the previous litter. During winter the wet walls of the lodge freeze and make the lodge almost impossible for predators to penetrate.
Where Do North American Beavers Live?
North American beavers are found in forested parts of Canada, the United States, and northern Mexico. The North American beaver population has dropped drastically over the years. North American Beavers were once estimated to number more than 60 million but are currently estimated to number between 6-10 million. The sharp population decline is attributed to extensive hunting for fur and glands that are known to have medicinal properties as well as pest control due to the beaver’s tendency to interfere with other land uses.
There is also a significant population of North American beavers found in Finland. The species was introduced in 1937.
Where Do Eurasian Beavers Live?
Eurasian beavers were once widespread across Eurasia but by the 19th century, they had been hunted to near extinction. Due to reintroductions throughout many European countries and on-going conversation efforts, the population had reached 639,000 individuals by 2003, of which 83% are found in the former Soviet Union. Today, Eurasian beaver populations can be found in Norway, Sweden, France, Germany, Poland, Estonia, Latvia, Belarus, Russia, with smaller populations in neighboring countries.
Conservation of Beavers
Efforts to conserve beavers began in Sweden in the 1920s in an effort that was meant to re-establish the Eurasian species in Europe, western Siberia, western China, and Mongolia. American beavers have also in recent times been reintroduced into territory that they once occupied during the colonial times.