Castor canadensis

Where do they live? Beavers are found throughout all of North America except for the northern regions of Canada and the deserts of the southern United States and Mexico. (Frazier, 1996) Biogeographic Regions

nearctic native



What kind of habitat do they need? Beavers live in lodges. They will either live in one built on an island, one built on the shore of a pond, or one built on a lakeshore. The lodge has one main room with its floor above water. There are two entrances to the lodge. (Encarta, 2004) The lodge is oven-shaped, and is made of sticks, grass, moss, and mud. The inside room may be 8 feet wide and up to 3 ft high. Over the years beavers add more sticks and mud. This makes the lodge larger. The floor of the lodge is covered in bark, grass, and wood chips. (Encarta, 2004) The pond lodge is built either a short way back from the edge of the bank, or partly hanging over it, with the front wall built up from the bottom of the pond. The lake lodge is built on the shelving shores of lakes. To ensure adequate water depth surrounding the lodge, beavers dam streams with logs, branches, mud, and stones. (Encarta, 2004; "Castor Canadensis", 2000) These animals are found in the following types of habitat

temperate

terrestrial

freshwater Terrestrial Biomes

forest Aquatic Biomes

lakes and ponds

rivers and streams

How do they reproduce? Beavers are monogamous, but if one mate dies, the other will "remarry", or seek out a new mate. Beavers are driven away from their colonies usually around their second year of life, right before a new litter is born. They then make a colony of their own, usually several kilometers away, and they first breed around their third years of life, give or take a year depending on the quality of the environmtnt. ("Castor Canadensis", 2000) Mating System

monogamous Female beavers are sexually mature when they are about 3 years old. They give birth to one litter each year, usually between April and July. Baby beavers develop inside their mother for about 3 months. Baby beavers are called kits. When they are born they already have all of the fur and have their eyes open. (Frazier, 1996; Frazier, 1996; Hall and Kelson, 1959) At birth kits are usually around 38 cm long including their tales. They tend to weigh from 250 to 600 grams and can be red, brown, or almost black. They remain in the lodge for a month, afterwards leaving for longer periods of time to swim and take in solid foods. Most beavers are weaned within two weeks, although it can take up to 90 days. The young usually stay with their parents for 2 years and then leave to make their own homes. (Frazier, 1996; Hall and Kelson, 1959; Whitaker and Hamilton, 1998) Key Reproductive Features

seasonal breeding

gonochoric/gonochoristic/dioecious (sexes separate)

sexual

viviparous How often does reproduction occur? Beavers breed once a year.

Breeding season Mating takes place during the winter season, usually in January or February.

Range number of offspring 1 to 4

Average number of offspring 3.5 AnAge

Average gestation period 3 months

Average gestation period 128 days AnAge

Average weaning age 2 weeks

Average time to independence 2 years

Average age at sexual or reproductive maturity (female) 3 years

Average age at sexual or reproductive maturity (female)

Sex: female 639 days AnAge

Average age at sexual or reproductive maturity (male) 3 years

Average age at sexual or reproductive maturity (male)

Sex: male 639 days AnAge Both male and female beavers will care for their young for up to two years. To prepare for new kits, a mother beaver will make a soft bed on the floor of the lodge. She will then use her tail to help deliver her babies. She licks each kit clean and nurses it. Both mother and father beavers will protect their young from predators, catch food for them, and teach them how to catch food on their own. (Encarta, 2004; Frazier, 1996) Parental Investment

pre-hatching/birth provisioning male female protecting male female

pre-weaning/fledging provisioning male female protecting male female

pre-independence provisioning male female protecting male female



How long do they live? Under favorable conditions, beavers will produce their first litters at two or three years of age. The average lifespan of a beaver in the wild is 10 to 20 years. While its size saves it from most predators, a beaver's lifespan can be cut short by predators, most commonly humans, wolves, and coyotes. Parasites and disease also play a factor in mortality. (Whitaker and Hamilton, 1998; Frazier, 1996; Whitaker and Hamilton, 1998) Typical lifespan

Status: wild 10 to 20 years

How do they communicate with each other? Beavers have a pair of anal scent glands, called castors, which secrete a musk-like substance called castoreum. This is used mainly for marking territories. The broad, flat, scaly tail is about 25 cm (about 10 in) long and serves as a warning signal when slapped against the water. Beavers also call out to others, making a low, groaning sound. (Encarta, 2004; "The Beaver", 2002) Communication Channels

visual

acoustic

chemical Other Communication Modes

scent marks Perception Channels

visual

tactile

acoustic

chemical

What do they eat? Beavers eat bark and cambium, the soft wood underneath bark. Their favorites include maple, willow, beech, birch, alder, and aspen trees. Beavers also eat plants that live in the water, including root and flowers. When beavers live in zoos, they are fed yams, lettuce, carrots, and "rodent chow". (Frazier, 1996; ; ) Primary Diet

herbivore lignivore

Plant Foods

leaves

roots and tubers

wood, bark, or stems

What roles do they have in the ecosystem? Beaver dams create ponds that provide homes for many other animals. They also raise the level of the water in the area and prevent damage from flood waters. (Frazier, 1996; ) Ecosystem Impact

creates habitat

keystone species

Do they cause problems? Although beavers are beneficial to the environment, they can destroy it also. Dams slow the flow of water in fast streams, changing the flora and fauna and sometimes creating silting. They may flood low-lying areas, sometimes causing extensive loss of timber. ("Data: Species: Mammal: American Beaver- Castor canadiensis", 1998)

How do they interact with us? Beaver fur has been a significant trade item for the last century, creating large amounts of money for merchants. Beavers are incredibly beneficial to the environment. They are instrumental in creating habitats for many aquatic organisms, maintaining the water table at an appropriate level and controlling flooding and erosion, all by building dams. See the Sevilleta Long-Term Eocological Research Project (LTER)/ RKM and KVP-- University of New Mexico account on the web at http://sevilleta.unm.edu/animal/mammal/beaver.html for a more detailed explanation of the benefits of beavers in the environment. ("Data: Species: Mammal: American Beaver- Castor canadiensis", 1998) Ways that people benefit from these animals:

body parts are source of valuable material

One of the earliest accounts of beaver natural history was written by Samuel Hearne in the late 1700s. His journal entry on beavers is online at: http://web.idirect.com/~hland/sh/an020.htm.

Contributors Tanya Dewey (editor), Animal Diversity Web. Rebecca Anderson (author), University of Michigan-Ann Arbor.