Castor canadensis-American Beaver

© rosalie-rick – (INaturalist)

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## **Size**

American Beavers are North America's largest native rodent. They have a head/body length of around 30 to 33.5 inches, with a tail of 10-14.5 inches. They range in weight from 24-57 Pounds. However, large individuals have reached weights of up to 86 Pounds. There is no sexual dimorphism in this species.

## **Description**

These animals are covered in glossy red-brown fur with small eyes and ears. They have long, dark-orange incisors, which can grow to 1 inch in length. It has a large, vertically-flattened tail, which is scaly and paddle-like. Its hind feet are webbed, while its front feet are not.

## **Range**

This rodent is found throughout much of North America, from Alaska and Canada south through most of the USA to north-eastern Mexico.

## **Range in South**

Native to most of the south excluding only the bottom 2/3rds of Florida and regions of western Texas.

## **Habitat**

American beavers are found in swamps, lakes, streams, and rivers in forested areas. Surrounding trees play an important role in materials for beavers' dens and dams.

## **Behavior**

American beavers are best known for their ability to cut down trees with their impressive incisors to use as construction materials. They are able to construct watertight dams using wood and mud. Dams may be built across fast-flowing streams, and long dams may cause large areas to be flooded. Beavers' dens, also known as lodges, are often surrounded by open water and are also made of wood and mud. These dens have 1-2 openings underwater that connect to a chamber slightly above the water level. These chambers are large, and are usually around 3 feet tall and 6-9 feet wide. Beavers are also known to create canals to transport wood across shallow water. American beavers live in colonies of up to 8 related individuals. They are most active from late afternoon to early morning. During the day, members of these beaver colonies rest, either in the den or in burrows dug into the bank. As expected, American beavers are excellent swimmers, and are well adapted to their aquatic environment. Some of these being their webbed hind feet, their paddle-like tail, the ability to close their nostrils and ears, and a membrane which covers and protects their eyes allowing them to see underwater. Some interactions between beavers include grooming, nose touching, or play-wrestling. Aggression is shown by hissing, grunting, and teeth grinding. Tail slapping is a behavior shown by beavers, and it is either used to frighten predators or alert nearby beavers of danger.

## **Reproduction**

Both sexes of this species reach sexual maturity at around 1.5 years of age, but they usually will not breed until they reach 2-3 years old. American beavers mate in pairs for life (monogamous), but if one member of the pair dies, the surviving member will find a new mate. Breeding occurs in winter, and a gestation period of roughly 107 days follows. Typically, 3-4 young are birthed in May or June, but births may occur in other months. Newborns are fully-furred, with their eyes at least partially open and their incisors erupted. At birth they weigh around 12-22 ounces. Weaning (independence of the young) takes place when the young are 6-8 weeks old. The young may disperse up to 9.5 miles from where they were born at around 2 years of age, but dispersals of up to 68 miles have been recorded.

## **Diet**

These beavers consume mostly bark in winter (aspen is a staple), and roots and green vegetation in summer. This vegetation includes plants such as cattails and water lilies.

## **Predation and Lifespan**

Humans are the primary threat to adult beavers, however domestic dogs, coyotes, bears, wolves, fishers, American minks, North American river otters, and long-tailed weasels may prey on young American beavers (kits). On average, the American beaver lives 5-7 years, but lifespans of over 20 years have been documented.

## **Status**

The American Beaver is listed as least concern by the IUCN, with a stable population. It is abundant throughout most of the south, and is even considered a pest in some areas. It was once heavily targeted for its fur and its populations were greatly depleted by the late 1800s, but they recovered well by the late 1900s. NatureServe lists it as stable throughout the south (in states with status listed), excluding Delaware, where it is listed as vulnerable.

## **References**

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 [Reid, F. A. (2006). A field guide to mammals of North America. Houghton Mifflin Company.]
2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 2.22 2.23 2.24 2.25 2.26 2.27 2.28 2.29 2.30 2.31 [Best, T. L., & Dusi, J. L. (2014). Mammals of alabama. University of Alabama Press.]
3. ↑ 3.0 3.1 [Whitaker, J. O. (1996). The Audubon Society Field Guide to North American mammals. Knopf.]
4. ↑ 4.0 4.1 4.2 [Anderson, R. (2002). Castor canadensis (American Beaver). https://animaldiversity.org/accounts/Castor\_canadensis/]
5. ↑ [Murie, O. J., & Elbroch, M. (2005). Peterson Field Guide to Animal Tracks. Houghton Mifflin.]
6. ↑ [ITIS. (2023). Castor canadensis Kuhl, 1820. https://www.itis.gov/servlet/SingleRpt/SingleRpt?search\_topic=TSN&search\_value=180212#null]
7. ↑ 7.0 7.1 [GBIF. (2022). Castor canadensis Kuhl, 1820. https://www.gbif.org/species/2439838]
8. ↑ [IUCN (2016). Castor canadensis. https://www.iucnredlist.org/species/4003/22187946]
9. ↑ [NatureServe Explorer. (2023). Castor canadensis. https://explorer.natureserve.org/Taxon/ELEMENT\_GLOBAL.2.100922/Castor\_canadensis]