North American beaver

Beavers live in North America.

They live in streams, rivers, ponds and lakes with trees nearby. They build a cozy home in the water called a lodge.

North American beavers live across the forested parts of North America, from Canada and Alaska south through the United States to northern Mexico. They need fresh water and trees: streams, rivers, marshes, ponds and the shores of big lakes.

Their home is called a lodge, a dome of branches plastered with mud. The doors are underwater, so the family can swim in and out without being seen, and the living room inside stays above the water.

The IUCN lists the species as native to Canada, the United States and Mexico, where it reaches the northeastern state of Tamaulipas. Britannica describes its range as the forested parts of North America to northern Mexico, including the southwestern United States and northern Florida.

People have also released American beavers outside their native range. Populations introduced to Finland have flourished and spread into the Russian republic of Karelia, and beavers released in Tierra del Fuego at the southern tip of South America in 1946 have spread across the islands of both Argentina and Chile; a 2020 study of aerial images counted about 206,000 of their dams there, many in southern beech forests. Where water is deep, beavers may dig bank dens instead of building island lodges.

A beaver's front teeth are orange and very strong.

Its back feet are webbed, like a duck's, for swimming. Its flat tail helps it steer. Its fur keeps it dry and warm in the water.

A beaver's big front teeth never stop growing, and they are orange because of iron in the tooth enamel, which makes them extra strong. The beaver's lips close behind its teeth, so it can gnaw underwater without swallowing water.

Its back feet are big and webbed for swimming, and its small front feet work like hands. When it dives, flaps close its nose and ears, and a see-through eyelid covers its eyes. A beaver can stay underwater for up to 15 minutes.

The chisel-shaped incisors have orange outer enamel in which iron replaces some calcium, making them unusually strong. Fur-lined lips close behind the incisors so a beaver can cut and carry branches underwater. On diving, valves close the nostrils and ears, and a transparent nictitating membrane covers the eyes; dives can last up to 15 minutes.

Propulsion comes from the large, webbed hind feet, while the dexterous front feet handle food. A split claw on the second hind toe works as a grooming comb, spreading oil from glands through dense underfur and long guard hairs to keep the coat water-repellent. The flat, scaly tail, up to about 45 centimeters long, stores fat and makes a loud alarm slap.

Baby beavers are called kits.

They are born in the lodge in spring. Mom and Dad look after them. Big brothers and sisters help too.

Beavers usually keep the same partner. In spring, after about 105 days, the mother gives birth in the lodge to a litter of kits, usually about four. A newborn kit is about 38 centimeters long, including its tail.

The kits grow up in a busy family. Older brothers and sisters, the yearlings, stay with their parents for up to two years and help with babysitting, collecting food and building. Beavers can start families of their own at about two or three years old.

Beavers are monogamous. In the north they mate between January and March; a single litter of one to nine kits, usually four, is born in spring after a gestation of about 105 days. Kits measure about 38 centimeters including the tail at birth.

A colony is an extended family of up to about eight: the adult pair, the kits of the year and the yearlings from the previous litter. Young beavers stay for up to two years, helping with care of their siblings, food collection and dam building, then disperse to find territories of their own. Under good conditions they first breed at two or three years old.