8 Fascinating Things to Know About Beavers

North American beaver chewing on a tree trunk.
North American beaver.

Troy Harrison / Getty Images

Beavers are one of the most well-known and recognizable rodents in the animal kingdom. There are two species of beavers, the North American and the Eurasian beaver. These semi-aquatic mammals have two large incisor teeth with a hard, orange-colored surface. Beavers are herbivores, with a preference for woody tree branches. The North American beaver is the largest rodent in North America, second only to the capybara

This nocturnal keystone species builds impressive dams and lodges, but is highly controversial due to damage and flooding they cause to man-made environments. From their vanilla-scented secretions to their amazing ability to alter an ecosystem, here are eight fascinating facts about beavers.

1. There Are 2 Beaver Species

Eurasian beaver on a log
Eurasian beaver. Gareth Goldthorpe / 500px / Getty Images

Two species of beavers exist in the world: the North American beaver and the Eurasian beaver. They are the only members of the family Castoridae, both in the genus Castor. The main differences between the two species is that the Eurasian beaver is a bit larger in size, with a larger, narrower muzzle. The underfur of Eurasian beavers is thinner and lighter than the underfur of North American beavers. North American beavers also tend to be darker in fur color.

2. They Are Most Graceful in Water

Beaver swimming in water carrying a small branch with leaves
Stan Tekiela Author / Naturalist / Wildlife Photographer / Getty Images

Beavers are not exactly smooth walkers. Their heavy build and short legs mean they need to waddle from point A to point B. Rather than outrun potential predators when on shore, they’ll scurry back to the water as quickly as possible, where their skill at swimming can easily deliver them from danger. Their webbed rear feet act like fins and their flat, oval-shaped tails work as rudders, helping them zip around the water at speeds up to five miles per hour.

Other adaptations that allow beavers to enjoy a semi-aquatic life include nostrils that close tightly when they're swimming, transparent third eyelids that allow them to see underwater, muscles in their ears so they can fold them flat to prevent water from getting in, and a thick, oily coat that keeps the water and cold at bay.

3. Their Tails Have Many Uses

Beaver carrying mud to its den with its paws using its tail as a rudder
Rejean Bedard / Getty Images

With a simple slap of their large, flat tail on the water, a beaver sends a warning to other beavers about pending danger. And it’s a handy rudder when swimming. But these aren’t the only uses for that thick, leathery tail.

The beaver’s tail is about 12 inches long and two inches wide. Such a big sturdy tail comes in handy when the beaver is on land. When a beaver stands on two hind legs to gnaw on branches or tree trunks, the tail acts as an extra leg, helping the beaver to balance. The tail can also be used as a lever when trying to drag bulky, heavy branches around the bank or into position in a dam.

While a beaver’s tail is a great tool, there’s one common misconception over how it's used. Beavers don’t use their tails to place mud in their dams, they use their hands and arms instead.

4. Beavers Secrete Vanilla-Scented Goo

Beavers make a chemical compound in a scent gland called castor sacs, located under their tails. They use this molasses-like goo, called castoreum, to mark their territory.

This secretion smells so much like vanilla that it has historically been collected for food flavoring and perfumes. While still approved by the FDA, most of the vanilla used globally (94 percent) is synthetic, and most manufacturers no longer use castoreum in vanilla extract, though it is still used by some perfume makers.

5. They Were Trapped Nearly to Extinction

historical photo of an agent holding beaver pelts
Ralston Dan H., U.S. Fish and Wildlife Service / Wikimedia Commons / Public Domain

Eurasian beavers nearly became extinct due to overhunting and habitat loss, with an estimated 1,300 beavers in the wild remaining in the beginning of the 20th century. The North American beaver was nearly wiped off the continent due to hunting for their pelts and castoreum. It's estimated that North American beavers once numbered between 100 and 200 million, but by the early 1800s, they were nearly gone. 

Reintroduction programs have been successful, and the population of the North American beaver is abundant throughout its range. The Eurasian beaver population is less abundant, but due to reintroduction and management efforts, Eurasian beavers are now established in France, Germany, Poland, and parts of Scandinavia and Russia.

6. Beavers Live in Elaborate Lodges

beaver lodge in lake
Karen Tweedy-Holmes / Getty Images

A beaver’s preferred habitat is one with plenty of water nearby, since that's how they stay out of reach of predators. Beavers build their homes, called lodges, on the banks or shores of lakes and rivers, or on islands in the middle of a waterway. 

The completed lodge is made of a mound of branches, logs, grass, and moss, plastered with mud. Each lodge has underwater openings that lead to tunnels and a central chamber. Beavers add to their lodges, which can reach over six feet in height and 39 feet in width, over time.

During the fall, beavers build food caches near their lodges that they fill with willow and aspen tree branches to get them through the cold winter months.

7. They Are Environmental Champions

Despite the controversy they can inspire, beaver dams are helpful in many ways. A study by scientists from the University of Rhode Island measured just one of the positive benefits of dams: They can help remove nitrogen from waterways. The chemicals, which are found in fertilizer, can cause algae blooms that deplete the supply of oxygen to fish and other aquatic species. The dams built by beavers create ponds that encourage aquatic plant and bacteria growth that can ultimately break down the nitrates and remove as much as 45 percent of these chemicals from streams and creeks.

A keystone species, beavers create beneficial habitats for other organisms by changing the flow of the watershed. Their dams control flooding and maintain a consistent water table.

8. Beavers Are an Ally Against Drought

Beavers dam in Argentina
Adwo / Shutterstock

The answer to reversing the effects of ruined waterways and worldwide water shortages may in part be thanks to this well-known rodent. Teaming up with nature's best waterway engineers could make a difference for water-parched places.

A study analyzing the impact of beaver dams in Rocky Mountain National Park found that the dams created by beavers raise the water table and cause water to spread through the valley, allowing it to stay moist even during dry seasons.

While beaver dams also have negative impacts on man-made infrastructure, the potential benefit of lessening the effect of droughts is a positive solution to water shortages and other effects of climate change.