Why Do Beavers Build The Most Amazing Dams?

why do beavers build dams

A beaver dam in Utah. Photo: Tom Kelly/Flicker.


Ever wonder why do beavers build dams? I know, it is not something you think about every day. But when you do…

Beavers want to protect their families just like we do which is one reason we love them. Let’s start at the beginning. What exactly is a beaver?

As North America’s largest rodents, they have bright orange teeth (learn why in our Beavers blog), webbed feet & long flat tails. One of the things we love about this misunderstood mammal is they mate for life are fiercely loyal to their families.

Living on ponds or streams, their flat tails help them swim but also can be slapped against the water’s surface to indicate danger is approaching. Reminding us of mini-submarines, they can stay underwater for up to 15 minutes. Compare that to us humans who can only hold our breath for about 2 minutes. But it’s nothing like the superpower of a sea turtle who can stay underwater for up to 7 hours when resting!


Beaver predators

why do beavers build dams

Beavers are mammals with cool long flat tails. Photo: Michael B/Flickr

Beavers have lots of predators. Everything from bears, eagles, mountain lions & wolves (and to see what else wolves eat, read our What in the World Do Wolves Eat? Think Blueberries!). And of course, the number one predator is us. Beavers have been hunted throughout the years for their pelts or killed as nuisances. So how do they avoid being eaten (or hunted) by all these predators?

Because they are slow-moving on land, but excellent swimmers, they build their houses, called lodges, in the water. The dams create ponds that slow the water down so it doesn’t wash away their house. And the beaver predators can’t get to them since their lodges have underwater entrances. How clever!


why do beavers build dams

Beavers build dams to create ponds in which they can build their houses to keep their families safe. Illustration: Encyclopedia Britannica

How do beavers build dams & lodges?

Beavers are often called ecological engineers. They are one of the few animals to manipulate their environment in order to survive. By cutting down trees using their incredibly strong teeth, they change the landscape. Then by damming up a stream, they manipulate the water to suit their needs.

So first, they drop trees in a stream resulting in the water slowing down. Then they gather branches, sticks & mud in their mouths &  swim out to the felled trees. Using their front paws, they construct a dam that stops the stream from flowing and creates a pond behind the dam.

Watch the video above to see David Attenborough (one of our conservation heroes) show you a beaver building a dam. Fascinating!

why do beavers build dams

Beavers love willow branches and will store them at the bottom of their pond for winter eating.

Some of the reasons for beaver dams

So beavers build dams to keep their homes and families safe. Why else do beavers build dams?

During winter, many beaver ponds freeze over. Beavers don’t want to leave their homes to gather food since they are targets for all those hungry predators. So they store food at the bottom of the pond. But how?

Beavers are herbivores, meaning they only eat plants. Their favorite beaver food is young sapling branches, especially the inner bark of aspen and willow trees.

Gathering twigs of fallen trees, they push the sticks in the mud at the bottom of their pond until ready to harvest and eat. When they need food, they simply swim out of their underwater entrance and bring the twigs back to their lodge. Ingenious.

Are beaver dams beneficial to the environment?

why do beavers build dams

A lake created by a a beaver dam. Photo: Alan English/Flickr

Beaver dams sometimes cause unwanted flooding in surrounding neighborhoods. One of the main reasons some people consider them pests. However, there are ways to prevent flooding by installing flow regulation devices in the dams.

And they cut down trees which can be unsightly. That’s the bad but wait, there is so much good…

Their dams create wetlands which are critical habitats for thousands of species. One US Fish & Wildlife estimate says over 60% of threatened species rely on wetlands to survive. As a result, beavers are considered keystone species.

Without beavers, the ecosystem they have created (all those wetlands) would be dramatically different or not exist. What other animals are keystone species? Think elephants, starfish & even oak trees. Really?  You can learn more in our blog The Amazing Benefits of Keystone Species.

Wetlands also help reduce forest fires since the earth is too wet to burn. And they improve water quality by purifying polluted waters and alleviating droughts. No wonder wetlands have been called the planet’s most valuable land-based ecosystem.

How can we live with beaver dam building?

beaver baffles

A beaver baffle is installed in a beaver dam. Photo: Tom Rogers/VTF&W

Now that we know beavers have a positive effect on the environment, how can we co-exist with them? A couple of things can be done to mitigate their damage to your property if they have taken up residence. 

First, you can install wire mesh fences around trees. This will help prevent them from being cut down by the enterprising beavers. Remember, they are just trying to protect their families. 

Second, in some cases, beaver baffles can be installed. The baffles allow some water to pass through the dam without hurting the wetlands behind the dam. 

Help spread the awareness about our beaver engineers

Help us spread the word about our amazing beavers. You can share their engineering feats with your friends, especially on social media.

Not only do they build dams, protect their families, and create wetlands, but they are some of the smartest, hardest-working animals we know. They are one of our true animal heroes, with great superpowers!

To learn more