Castor canadensis canadensis

Lodges built on islands, banks of ponds,and shores of lakes

Head and body: 25″ to 30″

Tail: 9″ to 10″

This is the largest rodent in North America. The head and body length is 25″ to 30″. A mature adult usually weighs 44 to 59 pounds, though they can be much larger.

The body is stout. The powerful hind legs are longer than the front legs so the rear end is higher than the front end when the beaver walks. The coat is reddish-brown or blackish-brown, glossy, and thick. The hind legs and have webbed feet. The claw on the second toe is doubled and functions as a comb.

The skull is disproportionately large. There are 20 teeth, including disproportionately large upper and lower incisors. The incisors are ¾″ to 1″ long and about ¼″ wide, and have chestnut brown enamel. The ears and nostrils are closable.

The tail is broad and flat—paddle shaped. It is 9″ to 10″ long, naked, and scaly.

Dams – A beaver will build a dam in a stream or river to slow the flow of water. Where sufficient stable water is available it will not build a dam but rather burrow into the bank. The front (downstream) side of a dam consists of large branches with the but ends facing downstream. Mud and debris make up the center of the dam. The back (upstream) side is made up of small branches.

Lodges – A lodge is a large pile of branches covered with mud, debris, and aquatic vegetation. It can rise up to 10 feet above the pond floor. It is excavated from within. In the winter, vapor can often be seen rising from a thinly covered opening used for ventilation (smoke hole) at the top of the lodge. Lodges are usually built near or at the edges of lakes and ponds.

Canals – A canal may be up to two feet wide and deep. It provides a safe water passage and can be used to help transport felled trees to the pond.

Cut trees – After downing a tree or branch a beaver may completely strip the outer bark to get at the cambium. Tree stumps near pond edges may show ¼″ wide incisor marks.

Scat – Beavers defecate in the water.

The stout build, brown fur, and flat, broad, scaly tail make identification unmistakable.

Bark, cambium, and small twigs of aspen, poplar, birch, maple, willow, beech, and alder. Aquatic vegetation.

Beavers are mostly nocturnal, though they are occasionally seen during the day. They are usually found in colonies of 4 to 10 related individuals.

Females usually breed first in their second year, sometimes in their third year. Gestation is 100 to 128 days. Between April and June the give birth to usually four or more kits, averaging five in Minnesota. The young remain with the parents until their second year, when they are either driven out or choose to leave. They usually relocate within six miles. The average life span is 11 years.

Subspecies
There were originally 25 subspecies of the American beaver (Castor canadensis). Through habitat degradation, population decline, reintroduction in some areas of Canadian beaver, and interbreeding, some of those subspecies may have been extirpated. Today, only one subspecies, Canadian beaver (Castor canadensis canadensis), occurs in Minnesota.