Discover the World’s Biggest Beaver Dam (Longer than Seven Football Fields!)

Written by Maxwell Martinson
Updated: June 3, 2023
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Stuffed deep in the middle of a boreal forest, far from all roads and hiking paths, a massive beaver dam plugs water from the Birch Mountains.

The dam is in the deep woods of Wood Buffalo National Park—Canada’s largest national park, and stretches the length of seven football fields, running just under 2,800 feet from end to end.

This is significantly longer than the Hoover Dam.

The dam area, which is the heart of a wetland, has a perimeter of around 6,500 feet. It’s in an interesting location as well, as it exists in the world’s largest inland freshwater river delta.

If you were to fly over it in a plane, you probably wouldn’t even know it was a beaver dam unless you had a trained eye. Still, it’s the largest beaver dam in the world.

Let’s explore this beaver-born masterpiece, gaining an appreciation for these wonderful little creatures along the way.

Wood Buffalo National Park Beaver Dam

The environment needs to support beavers, their food sources, and the running water that the dam blocks.

©Norikko/Shutterstock.com

Where Is the World’s Largest Beaver Dam, Specifically?

Wood Buffalo National Park is across northeastern Alberta and the bottom of the Northwest Territories. It is second in size only to Northeast Greenland National Park.

The territory of this park is more spacious than the entire country of Switzerland, and its borders were originally drawn to preserve one of the last herds of wood buffalo. The herd was, at that time, the largest in the world for that species.

That buffalo population has since diminished as a result of interbreeding with plains bison, but a small group remains. The park is also one of two nesting points for the only remaining self-sustaining population of whooping cranes.

There’s a lot going on in the park, so much so that the presence of the world’s largest beaver dam is often overlooked.

The dam is roughly in the middle of the park and there’s no way for humans to access it without wilderness skills or a private guide. The only easy way to witness it would be to fly over in a plane.

As a result of its isolation, nobody even knew it existed until researchers spotted it while examining satellite images. That’s right, you can see the dam area from some satellite images!

It wasn’t until 2009 that the Canadian parks department was notified and the dam was identified. And this was the first time anyone had seen it because it hasn’t been around for too long.

It then took 5 years for anyone to make the hike out to see it.

When Was It Created?

Surprisingly, the dam was created pretty recently. Antique maps and surveys of North America show us that beaver dams can exist for centuries. Some of the dams cited in the 19th century are still there.

There’s no telling how long a dam could last given the right environmental circumstances. The environment needs to support beavers, their food sources, and the running water that the dam blocks. Environmental forces change, though, and these structures don’t typically last forever.

Beavers sometimes migrate, build new dams, and so on and so forth. That’s why it wasn’t until recently that the largest beaver dam in the world was discovered—it’s estimated only to be a few decades old.

Why Do Beavers Build Dams?

We all know beavers build dams, but have you ever stopped to ask why? What’s so useful about putting a bunch of sticks and mud in a pile to stop running water?

Well, for one, the sound of running water is what triggers a beaver’s instinct to build a dam. A researcher named Lars Wilsson ran a study on two beavers who were raised in isolation.

They weren’t socialized to build dams, and they had never seen another beaver building a dam in the wild. For the first leg of the experiment, the beavers didn’t show any industrious dam-building behavior.

They were just, well, cute little beavers. Then, Wilsson brought the beavers to a source of heavy running water. The two individuals immediately, without a hiccup, built an exceptional dam together.

Next, he brought them to a quieter source of running water. The small stream ran at the pace of a trickle. In this instance, the beavers didn’t build a dam but rather tried to bury themselves in the wet, sloppy dirt.

Then, in another experiment with the same individuals, Wilsson played the loud sound of running water through a speaker placed on a concrete floor. The animals started building the dam over the speakers, attempting to cover up the sound of the running water.

They continued to build the dam there, even when Wilsson created a small and silent stream of water in their environment. The assumption made from these experiments was that the sound of the water was likely the catalyst for dam-building rather than the presence of running water in general.

In other words, beavers want to stop the sound of running water once they hear it. It could be like the feeling you get when you’re trying to read but there’s a fly buzzing about your head.

There’s no way you’re going to do anything until that buzz is gone. The same is true for beavers and the sound of a river, stream, or creek.

What do beavers eat - beaver with twig

the

sound

of running water is what triggers a beaver’s instinct to build a dam.

©P Harstela/Shutterstock.com

A Functional Irritation

This aversion to running water serves a couple of important purposes for beavers. First, it motivates them to start building a dam in the first place.

Then, once the dam is in place and doing its job, the sound of running water indicates a breach in the dam. In those moments, the impulse to repair the leak is integral.

If the beaver doesn’t repair the breach in the dam, the hole will only continue to get larger and erode the larger structure. If the structure fails and the water is left to follow its natural course, the wetland slowly drains and beavers lose their habitat.

Now, it’s not clear exactly what beavers are thinking when they hear running water. They might feel something like an irritation or an itch, but we just know that it prompts the dam-building behavior.

The impulse is wired into their biology, probably because dam-building creates a healthier environment for them to live in. Thinking in terms of natural selection, it makes sense that beavers who didn’t have the dam-building impulse would have suffered without the thriving ecosystems that dams produce.

How Ecosystems Benefit from Dams

It’s a good thing beavers hate the sound of running water. Dams provide countless benefits to North American ecosystems.

When a dam is constructed, it creates a wetland. Freshwater wetlands are one of the most important aspects of many inland ecosystems.

The dam slows the flow of water, causing it to build up and spread across the land rather than rolling downstream. The water then has time to seep into the earth and feed the water table.

This blockage and the resulting spread of water create a murky, swampy pool of water which is the only viable home for many aquatic plants and amphibians. Further, nearly every animal in an ecosystem benefits from the presence of a wetland.

That presence might allow some animals to grow and thrive, while other animals might get the majority of their food from wetlands. The impact is massive, and many wetlands would not exist without the presence of beavers. This makes beavers a keystone species.

How Beavers Benefit from Dams

Beavers benefit from dams because it creates a safe habitat for them. They are semi-aquatic animals that build lodges in ponds and wetlands.

Lodges are incredibly safe fortresses that allow beavers to sleep and raise their young. They’re comprised of hundreds, if not thousands of sticks and logs forming the shape of a mound.

The mound protrudes up out of the water and runs all the way down to the waterbed floor, and the entrance is underwater. So, the animal has to swim underwater and work its way up to the entrance of the lodge before entering its cove.

Beavers don’t live underneath their dams, though. The lodges are separate structures, but they’re typically near dams.

Without the impulse to build dams, though, these stick fortresses wouldn’t be possible. It also happens that dams and lodges are made of the same materials.

They’re so secure that the beaver’s common predators have almost zero chance of ever breaking in. Bears, coyotes, wolves, lynxes, hawks, and mountain lions have no way of effectively entering.

The First Person to Explore the World’s Largest Beaver Dam

Birch Mountains

On a macro-level, though, climate change is arguably the only thing that could impact this dam. If water sources from the Birch Mountains dry up in the wake of rising temperatures, for example, that could be harmful to these beavers and their dam.

©Kavram/Shutterstock.com

A man named Rob Mark was the first man to reach the dam in 2014.

His journey to this natural marvel was rife with seemingly mystical obstacles. The dense, unexplored foliage and muskeg hid monstrous bugs and marshland that served almost like quicksand.

He had to hike for three days to get there, and much of the terrain he covered required him to move particularly slowly. The beavers there wisely situated themselves in a maze of natural defenses that cradle the dam safely.

Plus, Mark was just an amateur explorer. He’s a man who enjoys taking a big trip every year and doing something special, and his 2014 trip took him where no human being had gone before.

He had even tried to traverse his way through the woods to the dam in previous years, but his map wasn’t perfectly accurate and his food supplies started running low, so he turned back.

His next trip was successful, though, even if it was extremely difficult. Apart from his maiden voyage, the dam has mostly been explored via satellite imagery or helicopter flyovers.

What Is the Dam’s Future?

As far as dams go, the world’s largest one is in a pretty safe position. There’s no chance that humans will develop the land it’s on. There’s also almost no chance that groups of humans will get anywhere close to it and impact the surrounding ecosystem on an immediate level.

On a macro-level, though, climate change is arguably the only thing that could impact this dam. If water sources from the Birch Mountains dry up in the wake of rising temperatures, for example, that could be harmful to these beavers and their dam.

It’s hard to predict its future, however, because we don’t have that much information about it. If you scour the internet for research on the subject, you’ll come up fairly dry.

This is because the dam is so new, so recently discovered, and so remote. It’s an incredible feat to get there, and even Rob Mark said there “wasn’t really anything to take a picture of.”

His quest was to stand where nobody else ever had, and that’s something that few people are willing to hike 3 days both ways to do.

So, it appears that the crafters of the world’s greatest beaver dam will remain in their masterpiece, feeding the local ecosystem with a healthy wetland, and doing so completely undisturbed for a long time.

Where Is Wood Buffalo National Park Located on a Map?

This Canadian park is accessible by car year round. It can be reached from Yellowknife or Edmonton via a series of highways. It is even accessible, weather permitting, by a winter road from Fort Smith to Fort McMurray and Fort Chipewyan. It is west of Lake Athabasca and north of Lake Clair.

The photo featured at the top of this post is © Dan-Pepper/Shutterstock.com


Sources

  1. Science.org, Available here: https://www.science.org/content/article/150-year-old-map-reveals-beaver-dams-can-last-centuries
  2. WorldCat, Available here: https://worldcat.org/identities/lccn-n90721250/
  3. MentalFloss, Available here: https://www.mentalfloss.com/article/561923/behold-worlds-largest-beaver-dam
  4. CBC, Available here: https://www.cbc.ca/news/canada/edmonton/world-s-largest-beaver-dam-explored-by-rob-mark-1.2771964
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About the Author

Hi! I'm Max and I'm a writer from Minneapolis, Minnesota. I've been freelancing for more than five years and love the freedom and variety that this profession offers. Animals are also a big part of my life, and a lot of my time is dedicated to playing with my cat, Herbie.

FAQs (Frequently Asked Questions) 

Where is this beaver dam?

Stuffed deep in the middle of a boreal forest, far from all roads and hiking paths, a massive beaver dam plugs water from the Birch Mountains. The dam is in the deep woods of Wood Buffalo National Park—Canada’s largest national park, and stretches the length of seven football fields, running just under 2,800 feet from end to end.

How can you reach the dam?

The dam is roughly in the middle of the park and there’s no way for humans to access it without wilderness skills or a private guide. The only easy way to witness it would be to fly over in a plane.

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.