Beaver Species Of North America

Beaver Description

The beaver is the largest rodent in North America and is built for water life. Adults can be up to four feet in length and over 60 pounds in weight. The beaver has webbed hind feet and a large-flat (almost) hairless tail.

When gnawing on trees, it uses its tail to help maintain its balance. To signal danger or to warn off predators, it will also slap its tail against the water.

With heavy claws, the beaver has short front legs. Their rear legs are longer, and they help propel themselves through the water using their hind webbed feet. Its nose and ears close up when the beaver is underwater, and a special membrane covers its eyes.

There is dark brown fur on the Beavers’ back/sides and lighter brown fur on the chest/abdomen. By coating itself with castoreum, an oily secretion from its scent glands, the beaver waterproofs its thick fur. Under its skin, the beaver has a thick layer of fat that helps keep it warm underwater.

Beavers have long, sharp incisor teeth at the top and bottom that they use to cut into trees and woody vegetation. Throughout the life of the beaver, these teeth develop. ¹Go To Source nhpbs.org -“Beaver – Castor canadensis”

Learn More: Nuisance Wildlife Species

Behavior Of North American Beavers

Beavers are herbivorous and semi-aquatic animals. Seeing beavers during the day is not uncommon. Still, they are usually nocturnal or crepuscular as they are often seen outside of dens/lodges, constructing or maintaining dams, and are very territorial.

Typically, a colony consists of 4-8 associated beavers, who resist additions or outsiders. However, for colony membership, close kinship is not a strict requirement. Recent genetic studies have documented unrelated individuals residing in a colony and unrelated lactating females sharing the same bank dens.

Young beavers are often displaced at about 2 years old from the colony shortly after they become sexually mature; however, dispersal age and patterns vary. In their first year, some beavers disperse, while others may remain for three years or more in the colony. Several ecological factors, including population, may influence this variation.

In order to start a new colony, beavers often disperse to another area, but some become “solitary hermits” inhabiting old abandoned ponds or farm ponds. Those not related to family units may be referred to as “floaters.” ²Go To Source aphis.usda.gov -“Beavers”

Dam-Building Beavers

Beavers are one of a few animals capable of modifying their habitat to suit their needs, other than humans. They quickly start building dams when beavers move into an area; they alter the habitat more to their liking.

The dam’s construction will cause flooding, resulting in surrounding timber to die and allowing other aquatic vegetation to grow. Beavers prefer to eat the plants that grow at the dam’s edges (willows, sweetgum, and blackgum). Therefore, almost anywhere there is a year-round source of water can be a suitable beaver habitat. ³Go To Source forestry.ca.uky.edu -“Beaver”

Canals Used By Beavers

To bring water closer to the stands of their favorite trees, beavers will excavate canals over a hundred feet long. This allows them to swim close to the trees and, if they feel danger, quickly retreat to the water. Furthermore, they use the canal to send edible branches back to the dam.

Beaver Reproduction

Beavers live in groups called colonies and are very social. One lodge typically holds the mating couple and their yearly offspring.

During the winter, from January until March, Beavers mate. The Eurasian beaver has a gestation period that lasts anywhere from 60 to 128 days. They then give birth to one to six children weighing approximately 8.1 to 22 ounces. The baby beavers are called kits. After six weeks of life, Eurasian kits are usually weaned.

The gestation period of American beavers is around 105 to 107 days. These beavers will give birth to one to four kits weighing between 9 and 21 ounces or so. In about two weeks, American beavers are generally weaned.

The kits leave the lodge at roughly 2 years of age and make one of their own. They find a monogamous mate at 3 years of age. ⁴Go To Source livescience.com -“Facts About Beavers”

The Social Hierarchy Of Beavers

The beavers of North America have a well-developed social hierarchy in which the basic unit is the family. In each family, the adult female is the central figure. The usual family group is comprised of the previous year’s kits and adults. The average family size is approximately 10 or 12 individuals. ⁵Go To Source nature.ca-“North American Beaver”

Beaver Diet

American beavers are herbivores (lignivores), feeding on beaver bark and cambium, the bark’s inner layer. The American beaver’s favorite trees are willows, aspen trees, alders, maples, and birches.

Beavers also feeds on aquatic plants, roots, and buds. Mammals normally can not digest cellulose, whereas it proves to be an important component of the daily ration of beavers. In zoos, you can see beavers fed by so-called “rodent food” as well as potatoes, lettuce, and carrots. ⁶Go To Source animalia.bio -“AMERICAN BEAVER North American beaver, Canadian beaver”

Habitat Of Beavers

In lodges, Beavers live. This species will construct their lodge on an island, the shore of a pond, or on the shore of a lake. There is one main room in the lodge with the floor above the water, and it has two entrances.

The lodge, which is made of sticks, grass, moss, and mud, is oven-shaped. It may be 8 feet wide and up to 3 ft high in the inner room. Over the years, beavers will add more mud/sticks and subsequently grows the lodge. The lodge floor is covered in chips of bark, grass, and wood.

Built on the shores of the lakes or a short way back from the edge of the water’s bank, the lodge is constructed with the front wall built up from the pond’s bottom. Beavers build dams with logs, mud, stone, and branches to ensure adequate water depth around the lodge. ⁷Go To Source biokids.umich.edu -“American beaver”

Beaver Range And Distribution

All over North America, Beavers are found. The only areas in which beavers can’t be found include deserts, peninsular Florida, and the arctic tundra.

Wherever aquatic habitats are found, Beavers can live. In Europe and northern Asia, Beavers once lived but went extinct in the 12th century. Today, in Norway, Poland, and Russia, beavers can be found.

Top 5 Predators Of Beavers

1. Wolves
2. Hawks
3. Coyotes
4. Mountain Lions
5. Bears

Human Interactions With Beavers

Due to human encroachment on wildlife habitats and a growing and expanding beaver population, beaver/human conflicts have increased in recent years. Because beavers have the ability to build water-impounding dams, they can change the environment in which they live dramatically. The two main problemed categories are tree cutting and flooding. Beaver activity may, in some instances, threaten property, agricultural crops, or public health and safety.

Other natural resources may also be negatively affected by beaver dams. For instance, Dams can act as barriers to migrating fish and cause flooding and siltation of rare plant and animal habitats.

There are also cases in which landowners are not prepared to tolerate any beaver activity on or near their property. Unfortunately, no repellents are effective against beavers, and harassment doesn’t cause beavers to leave a site. Continuous removal of dam material can persuade it to leave the site in rare instances, such as when a young beaver has not established a territory. ⁸Go To Source portal.ct.gov -“Problems with Beavers”

Beaver Species Found In North America

• North American Beaver Castor canadensis
• Eurasian Beaver Castor fiber

 

Sources:

1. “Beaver – Castor Canadensis – NatureWorks.” Nature Works, PBS, nhpbs.org/natureworks/beaver.htm. Accessed 21 Jan. 2021.
2. Taylor, Jimmy, et al. “Beavers.” U.S. Department Of Agriculture, U.S. Department of Agriculture Animal & Plant Health Inspection Service Wildlife Services, www.aphis.usda.gov/wildlife_damage/reports/Wildlife%20Damage%20Management%20Technical%20Series/Beaver-WDM-Technical-Series.pdf. Accessed 21 Jan. 2021.
3. “Beaver | Forestry and Natural Resources.” University Of Kentucky College Of Agriculture, University Of Kentucky, forestry.ca.uky.edu/beaver_damage. Accessed 21 Jan. 2021.
4. Bradford, Alina. “Facts About Beavers.” Livescience.Com, Future US, 13 Oct. 2015, www.livescience.com/52460-beavers.html.
5. “North American Beaver”. [Online]. Natural History Notebooks. Canadian Museum of Nature.
   Last updated 2016-11-25. (Web site consulted 2021-01-21).
   https://www.nature.ca/notebooks/english/beaver.htm
6. “American Beaver – Facts, Diet, Habitat & Pictures on Animalia.Bio.” Animalia, animalia.bio/american-beaver. Accessed 21 Jan. 2021.
7. Anderson, R. 2002. “Castor canadensis” (On-line), Animal Diversity Web. Accessed January 21, 2021 at http://www.biokids.umich.edu/accounts/Castor_canadensis/
8. “Problems with Beavers.” CT.Gov – Connecticut’s Official State Website, portal.ct.gov/DEEP/Wildlife/Nuisance-Wildlife/Problems-with-beavers#:%7E:text=The%20problems%20beavers%20can%20cause,negatively%20affect%20other%20natural%20resources. Accessed 21 Jan. 2021.