The beaver is a large rodent that spends much of its time in the water. The beaver is the second largest rodent species behind the capybara.
1. Scientific & Common Names
4. Present Status
Scientific & Common Names
Kingdom - Animalia
Phylum - Chordata
Class - Mammalia
Order - Rodentia
Family - Castoridae
Genus - Castor
Species - C. canadensis (North American beaver), C. fiber (Eurasian beaver)
Common Names - Beaver, American Beaver, Canadian Beaver
Beavers are quite large for rodents, growing up to four feet in length and weighing up to 60 lbs. As a mammal that spends much of its time in the water, the beaver has many unique feature that it has developed to adapt to its environment. It has a thick outer coat of fur that's very oily, making it water resistant, while its undercoat stays dry and helps keep it warm. Its front feet are used mainly for grabbing objects, but its hind feet are webbed to aid it in swimming. It also has a hairless paddle-like tail that it uses both for swimming, and to slap on the surface of the water to sound an alarm or warning to other beavers.
The beaver has specialized incisors (front teeth) that it uses to gnaw on wood. These teeth grow throughout the animal's life so that the constant gnawing doesn't wear them down completely.
Beavers are something of an oddity in the mammal community in that they are monogamous, meaning mating pairs stay together for life. They have a low birth rate, giving birth to between one and eight babies each year. The young stay with the family unit for up to two years. Mating occurs in the winter, and the young (called kits) are born in the spring.
Beavers are well-known for creating large housing structures called lodges. They use their teeth to gnaw through trees, and then use the fallen trees as wood to build their homes in the water, which can act as dams that are substantial enough to block the natural flow of rivers. The purpose is twofold: the lodge serves as a home base for a beaver family unit, while the dammed river will create a pond that provides an area of deep water for beavers to escape from predators. This deeper water is also less likely to freeze in the winter, providing a further refuge for the beavers.
Beavers eat plants, including leaves and buds, as well as the bark of the trees they gnaw to make their dams.
Until relatively recently in the fossil record, giant beavers were common in the Northern Hemisphere. Currently, only two species exist: the North American and Eurasian beavers. They both share common characteristics including webbed hind feet, a paddle-like tail, and a thick oily outer coat of fur. However, there are subtle differences that set them apart: for example, the Eurasian beaver tends to be larger, have a less oval-shaped tail, and has triangular nostrils, as opposed to the square nostrils of American beavers. Today, North American beavers have been introduced to several areas in Europe, though they are not genetically compatible with Eurasian beavers and the two do not hybridize.
Both species of beaver are currently considered "Least Concern". However, they have gone extinct in certain parts of their historical range, including Great Britain, and the Eurasian beaver was at one point nearly hunted to extinction. It has since rebounded after successful reintroduction efforts.
Beavers were hunted for their pelts, and a substance called castoreum, which the beavers secrete. This substance was believed to have medicinal properties, and was also used in perfumes and as a flavor enhancer for certain foods. In some areas, beavers themselves are also consumed as food. At one point, fur trapping was so lucrative that it is believed that much of the early explorations into Canada by Europeans was in order to find beavers. This led to beavers becoming endangered, but as the fur trade began to decline, beaver populations began to bounce back.
Animals: Visual Encyclopedia, Tom Jackson, 2011.
The Princeton Encyclopedia of Mammals, Edited by David W. Macdonald, 2006