font settings and languages

Font Size: Large | Normal | Small
Font Face: Verdana | Geneva | Georgia
Languages:

Castor canadensis

(Admiralty Beaver)

Interesting Facts

[ Back to top ]

Common Names

[ Back to top ]

Click on the language to view common names.

Common Names in English:

Admiralty Beaver, American Beaver, Beaver

Common Names in French:

Castor

Common Names in Russian:

Бобр североамериканский канадский

Common Names in Spanish:

Castor Americano

Description

[ Back to top ]

Physical Description

Species Castor canadensis

Beavers are stocky in body shape , with short legs and webbed hind feet. The naked tail is very wide, flat, and scaly .

Beavers are clearly rodents, with large chisel-shaped incisors. They can be prodigious woodcutters because the incisors are selfsharpening; the orange front layer is very hard enamel backed by a softer layer of white dentin. As beavers chew, those ever-growing teeth wear to a point rather than wearing flat. Beavers are the largest members of the rodent family in North America. Adults weigh about 50 pounds and are approximately 40 inches long. They have broad flat tails, which comprise roughly onethird of the body length . The fur is a rich brown above and slightly paler beneath . Beavers are highly adapted for aquatic life. A layer of fat protects beavers from the cold. Their fur is comprised of a very dense and fine wooly underfur which traps air and a layer of coarse thick guard hairs overlying this. Although the surface fur may wet, the insulating underfur remains very dry. Glands near the anus contain an oily substance called castor which beavers spread through their fur using specialized split toenails. Beavers also use this substance to mark territory. Castor has been used for centuries as a fixative agent in perfumes. Additional adaptations to aquatic life are the webbed hind feet, small eyes with a transparent inner lid which allows vision under water, and ears and nose that can be closed when beavers submerge. Beavers can remain under water for four or five minutes, with maximum dives up to 15 minutes.[1]

Color:

Fur on the upper parts is a rich reddish brown in the winter and darker in the summer. The belly is a pale buff gray.

Size/Age/Growth

This is the largest rodent in North America, with an average length of 0.9 - 1.2 m (3 - 4 ft ) and a weight of 13.6 - 31.8 kg (30 - 70 lbs ).

Habitat

Fabled in legend and lore, the Beaver is renowned as an industrious builder of dams to maintain a deep water pool around its lodge . The lodge is basically a round structure, made of branches sealed with mud and rising above the water surface. An underwater entrance leads to a cavity in the middle of the lodge above the water line . The lodge provides protection from predators and weather, and acts as a nursery for young.

Typically found at an altitude of 0 to 3,180 meters (0 to 10,433 feet).[2]

Biome: Terrestrial ; Freshwater

Ecology: These large rodents have much positive ecological impact . In the past, when beavers were common, their damming of small streams across the watersheds of North American rivers created a huge system of rain and snowmelt catchments which in turn modulated the flow and flooding of rivers. With the reduction of North American beavers by hunting and trapping - primarily for the fur trade- much more severe flooding now occurs on the lower reaches of these rivers.[1]

Beaver activity can cause damage to irrigation ditches and fruit orchards, but beaver dams are also highly beneficial. A dam can increase total water area, stabilize stream flow, prevent erosion, and provide resting, feeding, shelter and winter habitat for trout, and also habitat for other animals. When the pond behind the beaver dam floods, some trees die which then provide shelter for cavity nesting birds and other animals. The retention of water in beaver ponds causes the water table to rise and the soil to become waterlogged thus changing the plant community. Alder, willow and cottonwoods, trees that are staples of a beavers diet , colonize the area. The pond also creates habitat for other wildlife such as several fish species, mink, ducks, muskrats, and shorebirds. Beaver ponds gradually become filled with silt ; as they get shallower, the beavers may move elsewhere. Silt covered ponds leave behind fertile sites for grasses and will change over time into meadows. In the Pleistocene , beavers as big[1]

Biology

[ Back to top ]

Diet

The Beaver is generally active at night when it waddles up stream banks in search of leaves, twigs , the inner bark of sapling trees , and herbaceous plants to eat.

Beavers are herbivores; they feed on aspen, poplar, birch, willow and alder. They do not eat wood , but rather eat the layer of cambium tissue just below the bark. They twirl stems with their forefeet as their incisors slice off the bark much like humans eat corn-on-the-cob. They will also eat buds, roots , tubers of aquatic plants , and various herbaceous plants. Beavers may travel away from the water in search of food. If they find a rich food source, they will dig a canal from the source to their pond in order to transport the food. As winter approaches, cut twigs and small branches are pushed down into the mud at the bottom of the pond or stream near the lodge . As the water freezes over, the upper parts of the branches are held in place and the lower stems are preserved in the cold water for winter consumption . All family members contribute to the food cache .[1]

Reproduction

The Beaver breeds in January and February, and 1 - 6 young (called kits) are born 110 - 120 days later. Kits are born with fur, open eyes, and incisor teeth already erupted. Young are weaned in 6 - 8 weeks. They remain with the parents until they become sexually mature at 2 years of age. Beavers live as a family unit or colony of 4 - 12 individuals, consisting of adults , yearlings , and kits. A mated pair is monogamous (keeping only one mate) and may live together for 10 - 15 years.

Beavers reach sexual maturity at about 21 months of age. They mate for life with females doing the choosing after shoving contests with males. The females literally choose males they can push around. They breed in early spring and produce a single litter , usually four or five, per year. Gestation is about 120-days; in New Mexico young are born in April or May. Newborn beavers are born fully furred, with their eyes open; they weigh six to ten ounces . Shortly before the colony mother gives birth, the colony may drive out older offspring who will wander solitarily for tens to hundreds of miles along the river and its tributaries in search of mates and good colonization sites with ample food along the banks.[1]

Behavior

Depending on season and weather conditions, a Beaver may be seen in the daytime as well. When danger threatens, a Beaver will slap the surface of the water with its tail, producing a loud sound that serves to warn other Beavers. Many a late-night fisherman has been startled by the loud splash of a Beaver hitting the water's surface. The main predators of Beavers are the American Alligator, the Bobcat, and the Coyote. To escape a potential predator, a Beaver can remain underwater for 15 - 20 minutes. Beavers can influence the landscape in both positive and negative ways. They can be considered pests when they cut down valuable forest trees or feed on crops , but they can also benefit waterfowl and fish by creating ponds . Beavers will also excavate dens out of the banks of rivers or streams . Sometimes they become a nuisance by damming up man-made drainage ditches, culverts, and canals.

Beavers share with humans the ability to modify their habitat greatly. Their dams, a barrier of mud , logs , sticks and rocks, are built across shallow streams. Beaver dams may be six feet high and several hundred feet long. Ponds forms behind the dams. These protect beavers from predators and assure swimming areas beneath winter ice. Beavers also build large cone shaped lodges of sticks in deep water . These are held together and plastered with mud and are accessible by an underwater tunnel. A grass-lined nest chamber is built inside above the high water line . The thick lodge walls have great insulating power; the body heat from the animals inside results in 70- 90 degrees F in the main living chamber even in the winter. Along rivers, beavers seldom built stick dens, rather they make bank dens by tunneling into the bank at a point well below the water line, and then digging upward to create a chamber/nest inside the bank.[1]

Beavers live in small, closed family units known as colonies. A colony consists of four to eight related individuals, often a mated pair and several 1-2 year old offspring. An adult female is usually the dominant member of the colony.[1]

Contemporary beavers are largely nocturnal in their activities outside the lodge. It is debated whether this reflects their basic biology or behavior engendered by generations of being hunted - in areas with no human predators they are much more active in the daytime than in places where they are hunted and trapped.[1]

Parasites:

Beaver fur is home to flea-like beetles equally well adapted for a cold aquatic life. They feed on surface skin particles and apparently the larvae live in the beaver nest in the beaver house.[1]

Taxonomy

[ Back to top ]

Notes

Name Status: Accepted Name . Latest taxonomic scrutiny: 17-Aug-2000

Similar Species

[ Back to top ]

The Georgia Museum of Natural History and Georgia Department of Natural Resources

Members of the genus Castor

There are approximately 39 species in this genus:

C. accessor · C. caecator · C. californicus · C. canadensis (Admiralty Beaver) · C. canadensis baileyi · C. canadensis belugae · C. canadensis caecator · C. canadensis canadensis (American Beaver) · C. canadensis carolinensis · C. canadensis concisor · C. canadensis frondator · C. canadensis kuhl · C. canadensis mexicanus · C. canadensis michiganensis · C. canadensis missouriensis · C. canadensis pacificus · C. canadensis phaeus (Admiralty Island Beaver) · C. canadensis repentinus · C. canadensis shastensis · C. canadensis subauratus · C. canadensis texensis · C. fiber (Eurasian Beaver) · C. fiber albicus · C. fiber birulai (Dzungarian Beaver) · C. fiber caecator · C. fiber fiber (Eurasian Beaver) · C. fiber frondator · C. fiber galliae · C. fiber michiganensis · C. fiber pohlei · C. fiber subauratus · C. fiber tuvinicus (Tuvinian Beaver) · C. fiber vistulanus · C. issiodorensis · C. moschatus · C. plicidens · C. praefiber · C. subauratus · C. zibethicus

More Info

[ Back to top ]

Further Reading

[ Back to top ]

Notes

[ Back to top ]

Contributors

Data Sources

Accessed through GBIF Data Portal March 12, 2008:

Identifiers

Footnotes

  1. New Mexico Wildlife. New Mexico Department of Game and Fish Version of April 24, 2009. [back]
  2. Mean = 485.260 meters (1,592.060 feet), Standard Deviation = 559.890 based on 452 observations. Altitude information for each observation from British Oceanographic Data Centre. [back]
Last Revised: 2009-05-11