Beaver

Beaver species inhabit North America, Europe, and parts of Asia, living along streams, rivers, and lakes. The American beaver (Castor canadensis) and the Eurasian beaver (Castor fiber) share similar traits: dense waterproof fur, webbed hind feet, and broad, scaly tails used for steering, balance, and alarm slaps. Ever-growing incisors tipped with orange enamel slice through saplings and even thick cottonwood trunks. Beavers transport branches using their teeth and forepaws, swimming with heads held high as they ferry lumber to construction sites.

Dams are their signature structures. By piling sticks, mud, and stones across narrow channels, beavers slow water flow, raising upstream levels into ponds. These ponds provide deep water that protects beavers from predators such as wolves and bears. Within the pond, beavers build lodges—dome-shaped houses of sticks coated with mud. Underwater entrances lead to dry chambers lined with wood chips where families sleep and groom. In winter, ice seals the pond surface, but the water stays unfrozen around the lodge thanks to the insulating dam and the heat generated by the colony.

Beaver families consist of a monogamous pair, kits born that spring, and yearlings from the previous year who help gather food. Kits are born fully furred in late spring after a gestation of about 105 days. They leave the lodge within weeks, learning to swim under parental supervision. Young beavers disperse at age two or three to find territories of their own. The family maintains food caches by sticking freshly cut branches upright in pond bottoms, keeping bark accessible beneath the ice.

Ecologically, beavers are keystone species. Their ponds store floodwaters, recharge groundwater, and trap sediment, improving water quality. Wetlands created by beaver activity host dragonflies, waterfowl, moose, and trout. During drought, beaver ponds hold moisture that can slow wildfires and provide drinking water for wildlife and livestock. However, dams can also flood roads or culverts, creating conflicts with landowners. Wildlife agencies manage these issues by installing flow devices that allow water to pass through dams without the need to remove the beavers.

Historically, beaver trapping drove the fur trade that shaped North American and Eurasian exploration, nearly wiping out populations by the 1800s. Conservation laws, reintroduction programs, and shifting attitudes have restored beavers to many watersheds. Today, researchers partner with Indigenous communities and farmers to place artificial beaver dams that jump-start wetland recovery. Students can map local streams to identify suitable habitat, build scale models of dams to test water flow, or measure how beaver ponds change plant diversity. Understanding beavers as natural engineers encourages coexistence and highlights nature-based climate solutions.