American Beaver

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Photo by: Patrick Connolly

Species: American beaver

Scientific name:Castor canadensis

Status: common

Description: Beavers are the largest rodent in North America, and the 2nd largest rodent in the world (1st being the capybara). Beavers are very distinct looking; they are large, chunky, solid rodents, with oily brown fur. They can weigh as much as 32 kg and may be over 1 meter long.  They have a flat, scaly tail, short limbs (arms and legs), short neck, beady eyes, and a broad head with short ears, and large teeth (orange in colour). The underbelly of the beaver is lighter in colour than its top. They have large hind feet that are webbed, and used for swimming. The front paws are smaller, not webbed and have long claws that are used for digging.

Habitat: Beavers are found near freshwater environments. They need a habitat that has a water body with deciduous trees or shrubs nearby.  

Breeding: Beavers produce “lodges” made of mud and sticks which they use as their den. Building these lodges is intricate. The beaver will make a mound of mud and sticks in their aquatic habitat, and then they will chew an underwater tunnel and will hollow out a den in the centre. Lodges are strategically placed away from the shore in calm water, if it must be placed in flowing water, it will be found at the bank. Beavers may also dig a den in the bank of a waterbody and will live there. These lodges/dens are critical for breeding. A beaver is monogamous and will keep a single mate for their life. It is the job of the female to find a home site and is the central figure in a beaver family. Beavers will mate mid winter (January-February). The gestation (time that fetus develops) is four months. Before giving birth, the female will make the male leave the lodge. Usually females will give birth to a single litter of 4 kits (baby beavers) in May or June, but a second litter may occur in some years. A birth, kits are fully furred, have functioning teeth, open eyes, and can walk and swim. The kits will not leave the lodge until 1 month old. Young of beavers will remain with their parents until they are 2-3 years old. At this age they are sexually mature and will leave their parents to find their own mate and establish their own lodge.

Diet: The diet of the beaver may change with season. During the summer months they will eat aquatic vegetation, grasses, herbs, and fruit. During the winter, beavers will eat the food caches (storage) they have accumulated the previous fall. They will start preparing caches in September/October in cold regions, usually when the first frost occurs. The winter cache will be in the deep water close to their lodge. The cache will consist of trees, as they eat primarily bark and cambium from woody trees. Their favourite trees are aspen, poplar, willow, alder and birch.

Threats to species: Beavers are a common prey species for terrestrial (land) mammals, including wolves, coyotes, bears, lynx and wolverines. They are more susceptible to predation on land, when they are foraging (looking for food), because they are much slower on land. This is also a common species trapped for their fur. They can also be hit by cars when bodies of water are transected (cut) by a road.

Threat to humans: Beavers can cause quite a bit of damage due to their behaviour. Beavers will make dams to increase water depths in their habitat. This may cause flooding of farmlands, roads, and tree plantations.

Fun facts:

A beavers teeth continually grows throughout its life.

Beavers can cut down hundreds of trees in a single year.

When threatened, the beaver will slap its tail in the water, this communicates an alarm to their family.

They beaver has valves that will close their ears and nostrils when they are submerged (under) in water.

Beavers are one of a few mammals that can alter their habitat to their preference by making dams, cutting forests, and flooding small bodies of water.

Trappers use a “secret trick” to get beavers into their traps. They will make a hole in the dam; the sound of running water will lure the beaver back to fix the hole, where a trapper will place a kill trap.

Sources: 

Hinterland Who’s Who- http://www.hww.ca/en/species/mammals/beaver.html

Eder, Tamara, and Kennedy, Gregory. 2011. Mammals of Canada. Lorne Pine Publishing. Edmonton, Alberta.

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