“Beavers are the second-largest rodents on Earth, weighing up to about 60 pounds or more. They live in family colonies, eat bark, twigs, and water plants, and build dams and lodges that create ponds and wetlands. Scientists call them a keystone species because so many animals depend on the habitats they make.”
Few animals reshape their surroundings like beavers. With nothing but teeth, mud, and determination, a family of beavers can turn a trickling stream into a pond teeming with fish, frogs, birds, and insects. They’re also among the closest things the capybara has to a rival for the title of biggest rodent. Here’s everything you need to know about these remarkable engineers.
Beaver Quick Facts
| Trait | North American Beaver | Eurasian Beaver |
|---|---|---|
| Scientific name | Castor canadensis | Castor fiber |
| Weight | About 24 to 70 lb | Similar, about 24 to 66 lb |
| Body length | About 29 to 35 in, plus a flat tail | Similar |
| Range | Most of North America | Europe and parts of northern Asia |
| Lifespan in the wild | Around 10 years | Around 7 to 10 years |
| Diet | Herbivore | Herbivore |
The two species look nearly identical but can’t interbreed. They differ in chromosome number and some details of skull shape and scent glands.
Built for Life in Water
- Webbed hind feet power them through water.
- A flat, scaly tail works as a rudder, a prop for balance when sitting upright, a fat store, and an alarm signal when slapped on the water.
- Transparent eyelids act like built-in goggles.
- Valves close their ears and nostrils underwater.
- Lips close behind their front teeth, so they can gnaw underwater without swallowing water.
- Breath-holding: beavers can stay underwater for about 15 minutes.
Compare these adaptations with the capybara’s in our capybara vs beaver comparison and capybara swimming guide.
Why Are Beaver Teeth Orange?
Beaver incisors have iron-rich enamel on the front surface, which gives them a distinctive orange color and makes them tougher and more resistant to wear. Like all rodent teeth, they never stop growing, so constant gnawing keeps them the right length. Read more about rodent teeth and anatomy.
What Do Beavers Eat?
Beavers are herbivores. In summer, they eat leaves, grasses, aquatic plants, and roots. In fall and winter, they rely on the inner bark and twigs of trees such as aspen, willow, poplar, birch, and maple. Before winter, many beaver families build an underwater food cache near the lodge, anchoring branches in the mud so they can reach food under the ice.
A common myth says beavers eat fish. They don’t. Our rodent myths article busts a few more.
How Beavers Build Dams
Beavers build dams to raise the water level, creating a deep pond where they can swim safely and store food. They start with sticks and branches, then pack the gaps with mud, stones, and plant material. The sound of running water seems to trigger dam-building, which is why beavers quickly patch leaks.
Some beaver dams are enormous. One dam in Canada’s Wood Buffalo National Park has been measured at roughly 2,800 feet long, visible from space.
Beaver Lodges
A lodge is the family home. It’s a dome of sticks and mud, usually surrounded by water, with underwater entrances that keep predators out. Inside is a dry living chamber above the waterline, sometimes with a vent at the top for fresh air. In some places, beavers dig burrows into riverbanks instead of building a freestanding lodge.
Beaver Family Life
Beavers live in colonies made up of a monogamous adult pair and their offspring from the current and previous year. Young beavers, called kits, are born in spring and stay with the family for about two years, helping with repairs and caring for younger siblings before leaving to find their own territory. Families mark their territory with scent mounds made of mud and a secretion called castoreum.
Why Beavers Are a Keystone Species
Beaver ponds create wetlands that support a huge range of wildlife, from fish and amphibians to waterbirds, otters, and moose. Their dams also:
- Slow floodwaters and reduce erosion
- Store water through dry seasons
- Recharge groundwater
- Filter sediment and pollutants
- Create firebreaks of green, wet habitat
That’s why many conservation projects now reintroduce beavers or use “beaver dam analogs” to restore streams. Learn how rodents shape habitats in why rodents matter to ecosystems.
Beavers and People
Beaver fur drove much of the early North American fur trade, and heavy trapping nearly wiped out beavers in many regions by the late 1800s. Eurasian beavers faced similar declines. Protection and reintroductions have helped both species recover, and beavers have returned to parts of Britain after centuries of absence.
Beavers can cause problems, too, flooding roads and farmland or cutting down prized trees. Flow devices and tree guards often solve these conflicts without removing the beavers. See humane ways to manage wild rodents.
Beavers introduced to Tierra del Fuego in South America have become a serious invasive species there, a story we cover in invasive rodent species.
Beaver vs Other Semi-Aquatic Rodents
Beavers are often confused with muskrats and nutria. Beavers are much bigger and have flat, paddle-shaped tails; muskrats have thin, flattened tails; nutria have round, rat-like tails. See beaver vs muskrat vs nutria.
A Year in the Life of a Beaver Family
- Spring: Kits are born inside the lodge, usually in litters of about two to four. Last year’s young help care for them, and the family feeds on fresh green plants.
- Summer: Beavers graze on leaves, grasses, and water lilies, and repair dams as water levels drop.
- Fall: This is the busiest season. Families cut trees, build the winter food cache, and add fresh mud to the lodge, which freezes into a hard, predator-proof shell.
- Winter: Beavers stay inside the lodge and swim under the ice to reach their food cache. Their body fat, much of it stored in the tail, helps them through the lean months.
Beaver Predators
Adult beavers are big enough to discourage many predators, especially when they stay close to water. Wolves, coyotes, bears, and cougars take beavers on land, while young kits can fall prey to otters, bobcats, lynx, and large birds of prey. The tail slap on the water is a loud alarm that sends the whole family diving for safety.
Where to See Beavers
Look for signs rather than the animals themselves: gnawed stumps with pencil-point tips, wood chips at the base of trees, dams across streams, and dome-shaped lodges in ponds. Beavers are most active at dusk and after dark, so a quiet evening by a beaver pond gives you the best chance of spotting one swimming with just its head above water.
Frequently Asked Questions
Are beavers the biggest rodents?
No, they’re second. The capybara is the largest living rodent. See our rodent size chart.
Do beavers hibernate?
No. They stay active all winter, living in their lodge and feeding from their underwater food cache.
How fast can a beaver cut down a tree?
A beaver can fell a small tree in minutes; larger trees can take several nights of work.
Are beavers dangerous?
They avoid people but can bite if cornered. Give them space.