Beavers: 8 Things to Know About Nature's Most Impressive Landscape Engineers

Beavers have an unmistakeable tail. . Zadiraka Evgenii/Shutterstock

Beavers are one of the most well-known and recognizable critters in the animal kingdom. But beyond their bucked teeth and busy behavior, what do you really know about them? From their Swiss Army knife of a tail to their power to shift the biodiversity of ecosystems and alter the level of water tables, here are eight of the most fascinating characteristics of beavers that just might change the way you think about them.

There are 2 species of beavers in the world

There are just two species of beaver in the world.
There are distinct differences between the two species of beaver. grusgrus444/Shutterstock

Because the beaver is so much a part of the relatively recent history of North American economy and politics, thanks to the widespread trapping of beavers for their thick fur, it's easy to forget that there's more than one species of beaver. The North American beaver is a cousin to the Eurasian, which also played a role in the long trade history of Europe and Asia. These two species are the only members of the family Castoridae, both in the genus Castor.

While they may look similar, they are distinct enough that they cannot interbreed. (There were nearly 30 attempts in Russian to hybridize the two species, with no success.)

The main differences between the two species is that the Eurasian beaver is a bit larger in size, with a larger, narrower muzzle. They have thinner and lighter underfur than North American beavers. North American beavers also tend to be darker in fur color.

Awkward on land, but graceful in the water

Beavers are speedy swimmers and are made for a life in the water.
Beavers are made for a life in the water. grusgrus444/Shutterstock

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 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 5 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 and prevent water from getting in, and a thick, oily coat that keeps the water and cold at bay.

Beavers have many uses for their flat tails

Beavers have an unmistakeable tail.
Beavers have an unmistakeable tail. Zadiraka Evgenii/Shutterstock

Many of us already know of that famous slap of a beaver’s tail on the water, which sends a warning to other beavers about pending danger. And of course the beaver’s tail comes in handy as a rudder when swimming. But these aren’t the only uses for that thick, leathery tail.

The tail can grow to be 15 inches long and 6 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.

A beaver’s tail is a great tool, but there’s one common misconception over how it's used. “Contrary to common belief, beavers do not use their tails to plaster mud on their dams,” says the Washington Department of Fish and Wildlife.

Beavers secrete a vanilla-scented goo used in food flavoring

Castoreum is an FDA-approved food flavoring.
Castoreum is an FDA-approved food flavoring. H. Zell/Wikipedia

This is perhaps the weirdest fact you’re ever going to hear about beavers: They make a chemical compound in a scent gland called castor sacs, located under the tail. It's a molasses-like goo used to mark their territory, and most surprisingly, it smells like vanilla.

This secretion, called castoreum, is approved by the Food and Drug Administration (FDA) and is sometimes used in food flavorings as a substitute for vanilla flavor. It's sometimes added to cigarettes. Consumption of castoreum is very low, however, in no small part for how it's obtained.

“[G]etting a beaver to produce castoreum for purposes of food processing is tough. Foodies bent on acquiring some of the sticky stuff have to anesthetize the animal and then ‘milk’ its nether regions,” reports National Geographic. “Due to such unpleasantness for both parties, castoreum consumption is rather small — only about 292 pounds (132 kilograms) yearly. That statistic includes castoreum, castoreum extract and castoreum liquid, according to Fenaroli’s Handbook of Flavor Ingredients."

Castoreum has also been used in perfume making, and it was believed to have medicinal properties that could aid headaches, fever, low blood pressure and a wide range of other ailments. Of course, we now know it isn’t medicinal in any way.

Beavers were trapped to the point of disappearing

Beaver pelts were highly valued for centuries, and drove the steep decline of beaver populations across the continent
Beaver pelts were highly valued for centuries, driving the steep decline of beaver populations across the continent. Ralston Dan H, U.S. Fish and Wildlife Service/Wikipedia

Beavers were heavily trapped in North America after Europeans arrived. Their pelts were in high demand for the fashion industry in Europe, and their castoreum was used for a variety of purposes. But what may come as a surprise is the extent to which they were hunted. The beaver was nearly wiped off the continent. It's estimated that they numbered between 100-200 million when Europeans arrived and by the early 1800s, they were nearly gone. Indeed, much of the western exploration of the U.S. was driven by trappers looking for beavers after eastern populations disappeared.

Today, after significant conservation efforts starting in the mid-1900s, numbers have rebounded to an estimated 10-20 million.

Eurasian beavers have been heavily trapped as well, also for fur and castoreum. In fact, they were so heavily trapped that they became extinct in the United Kingdom for 400 years. Several thousand now live along the Elbe and Rhone, and they are rebounding in other parts of Europe. In Great Britain, they were reintroduced in Gloucestershire in October 2005, Lancashire in 2007, and they were reintroduced in Scotland in 2009.

The reintroduction of beavers to their old habitat is tenuous, however, because their ability to turn large areas of dry land into wetlands isn’t necessarily welcomed by the current human residents.

Beavers can turn forests into ponds and meadows

Beavers are industrious animals and are responsible for clearing patches of forest into wetlands and meadows.
Beavers are industrious animals and are responsible for clearing patches of forest into wetlands and meadows. Henrik Larsson/Shutterstock

"Beavers' ability to change the landscape is second only to humans," according to the Beavers: Wetlands and Wildlife website. Indeed the scope and long-lasting changes that a beaver family can bring to an ecosystem is incredible.

A beaver’s preferred habitat is one with plenty of water, since that's how beavers stay out of reach of predators. If a beaver moved into a forested area that's a little too dry for its liking, the beaver simply gets to work changing the landscape to suit its needs. By damming up streams and creeks, a beaver cuts down forest and creates huge ponds that provide water to other wildlife even during the height of summer. When they leave an area, and the dam breaks down, the flooded area dries and becomes a meadow.

"Beavers have a tremendous impact on ecosystems,” writes Live Science. “Dams alter the flow of rivers and can flood hundreds of acres... As sediment and debris build up, carbon increases and nitrogen decreases. The chemical changes alter the type of invertebrates, and the new water source attracts new species of birds, fish and amphibians. Flooded timber dies off and a forest becomes an open water ecosystem.”

Because of their impact, beavers can be highly controversial animals. As they return to habitats where they once flourished, they take no notice of the people who have built houses, roads and entire towns within the flood zones their dams create. Beaver damage costs Americans an estimated $100 million every year. Pest control companies are often called to trap beavers whose industrious work isn’t appreciated by nearby homeowners. While many celebrate the return of beavers, their presence causes grumbling when their engineering feats and our engineering feats collide.

Beaver dams help with pollution

A reduction in pollution is smong the many effects beaver activity has on landscape.
A reduction in pollution is among the many effects beaver activity has on landscape. Johnny Adolphson/Shutterstock

Despite the controversy they can inspire, beaver dams are helpful in many ways. A recent study by scientists from the University of Rhode Island measured just one of the positive benefits of dams: They can help remove up to 45 percent of harmful nitrogen from streams and creeks.

According to the Potomac Conservancy:

Nitrogen is one of the most problematic pollutants in the Potomac and the Chesapeake Bay. Nitrates, nitrogen-based chemicals found in fertilizers and other chemical compounds, wash off agricultural and urban areas after rain in the form of polluted runoff. Wastewater treatment plants also contribute to the problem. These chemicals cause algae blooms, which in turn result in dead zones, underwater areas devoid of oxygen where fish and other aquatic life struggle to survive.

The ponds that build up behind beaver dams encourage aquatic plants to grow, and their decomposition at the bottom of the pond encourages bacteria growth, the study found. The bacteria breaks down these nitrates, releasing nitrogen as a gas. The result is cleaner water, all thanks to beavers.

"I think what was impressive to us was that the rates were so high," Arthur Gold, lead researcher of the study, told Nature World News. "They were high enough and beavers are becoming common enough, so that when we started to scale up we realized that the ponds can make a notable difference in the amount of nitrate that flows from our streams to our estuaries."

Beavers are a key ally against drought

Beavers could be one of our best allies against drought.
When it comes to drought, beavers are not the enemy. Adwo/Shutterstock

How can we reverse the effects of ruined waterways, prevent worldwide water shortages and revitalize drought-stricken areas with fresh water? The answer may be in part in this well-known rodent. Teaming up with nature's best waterway engineers could make a difference for water-parched places.

As mentioned in a previous beaver fact, the activity of beavers damming up creeks and rivers raises the water table. A recent three-year study by Cherie Westbrook of Colorado State University and colleagues there and at the U.S. Geological Survey in Fort Collins, Colorado looked at the impacts of beaver dams in Rocky Mountain National Park. They found several interesting results that change our understanding of how beavers contribute to the groundwater system.

Within the valley, the dams cause water to spread toward the sides of the valley, rather than rushing through the valley with the river, which not only raises the water table but keeps more of the valley moist, even in dry seasons. According to Science Daily, “The researchers suggest that the elevated moisture levels found in soil surrounding the dams would otherwise require water from a very large natural flood, which they estimate as the 200-year flood, to achieve the same expansive water availability to the valley bottom.”

"This study broadens the view of the importance of beaver in the valley bottoms beyond the upstream ponds," Westbrook told Science Daily. "We found that upstream ponds were not the main hydrologic effect of the dams in the Colorado River valley. Instead, the beaver dams greatly enhanced hydrologic processes during the peak flow and low flow periods, suggesting that beaver can create and maintain environments suitable for the formation and persistence of wetlands."

While many people understandably complain about the impact that can have on man-made infrastructure, it also has an impact that we'll soon come to deeply appreciate: Beaver dams can help reduce the impact of droughts. With longer and more severe droughts occurring due to climate change, that ability is one that is heartily welcomed by those looking for solutions to water shortages. A report from WildEarth Guardians discusses an entire strategy to utilizing beavers in climate change adaptation, including encouraging beavers back into national forests where they once lived.

Now that beavers are returning to areas they were once trapped out of, whether actively encouraged or not, we may see an impact on a larger scale in protecting drought-prone areas from suffering through the worst of droughts.