Busy Beavers: Nature's Ecosystem Engineers

The scale of the projects undertaken by these "ecosystem engineers" might be smaller than those of humans, but when busy beavers get to work they create wetlands habitat that in turn supports a wide diversity of wildlife.

| June/July 2010

It’s a blue-skied, early-autumn day and I’m tromping a creek-side trail deep in western North Carolina’s Pisgah National Forest. For years, I’ve been drawn to these treed slopes and tumbling streams. Today, though, I’m neither fishing, nor backpacking, nor hunting mushrooms — my usual excuses for wandering the woods. Instead, I’ve come to check on a hard-working family of "ecosystem engineers" that moved to the neighborhood a decade ago.

I round a bend, and a downed tree blocks the trail, its gnawed end and pencil- stubbed stump telling me I’m nearing my destination. I step over it and proceed past more tooth-whittled trees. As I top a rise, the woods open and the landscape transforms. Before me lies a still pond of some 5 acres, with a broad margin of grassy marshland. A few yards from the high bank where I’m standing, a jumble of logs, sticks and mud blocks the creek, slowing the flow to a relative dribble of its upstream rush and tumble. This is the beavers’ dam, built to provide deep, still water for a safe home. I don’t see the rounded dome of a stick-built lodge. These busy beavers, like many another, instead may have burrowed into a bank underwater, then up, to hollow out a subterranean home. Tall, dead trees rise from the pond that slowly killed them, their bleached trunks pocked with cavities drilled by woodpeckers, but now used by birds and other creatures for shelter.

I move to a log and sit down in the sun. Tap-tap-tap. A downy woodpecker shinnies up one of the old trees, mining for insects. A breeze stirs the marsh grass. Dragonflies flash at the water’s edge. Ahhh. I’ve come here for this — not expecting to see beavers, which are mostly nocturnal, but to soak in the results of their work. A beaver pond is an extraordinary place, peaceful during the day and a center of activity at night.

It’s also the perfect place to consider the beaver itself — an animal regarded by some as a pest and by others as an environmental savior. For centuries the beaver has shaped not only our landscapes, but also our history and our attitudes towards wildlife.

Just a Humble Rodent

Wildlife biologists came up with the "ecosystem engineer" classification for beavers: a species able to alter its environment to suit its needs. In that capacity, beavers are perhaps second only to humans. But unlike humans, beavers are driven not so much by intent as by instinct. It’s the sound of running water, for example, that stimulates a beaver to build or repair a dam. And their legendary ability to fell trees in a particular direction? Not so. A beaver simply gnaws until the tree falls — sometimes on the beaver.

A busy beaver is just a humble rodent going about its biological business — for which it’s extraordinarily well-equipped. It’s the beaver’s bulk, for instance, that helps it bulldoze mud, rocks, and logs into place. Only one other rodent in the world — South America’s capybara — is larger. An adult beaver weighs between 40 and 60 pounds. A rare few have approached 100 pounds.

Lydia McD_2
7/21/2010 10:35:23 AM

Thanks so much for this article. I live on a creek in semi-rural West Virginia, and just bought this property last fall. Ever since I moved in beavers have been hard at work damming the creek, and I've been a little lost as to whether or not it's an issue to be dealt with or a plasurable addition to the active wild culture around me. Part of my fears came from backpacking the past couple of years through parts of Chilean Patagonia, where beavers have decimated hundreds of miles of otherwise pristine forest after being set free several decades ago post a failed attempt at fur trade. Considered a menace countrywide, they now reside on local menus as tourist chow for the experimental. Reading an article which cast them as a positive addition to a healthy ecosystem was a bit of a relief, because there is nothing in me that wants to destroy their home, much less them. They have done very little visible damage to the area surrounding the creek, and I do wonder if that will change, but I'd much rather protect the trees than harm the beavers. I'm open to any advice in regards to maintaining this coexistence. The commenter's story before mine was truly sad and I'm happy that my property can be a place where humans and creatures can coexist with little upset.

6/11/2010 4:08:39 PM

I remember when I was a kid in rural Pennsylvania, we had a beaver family that moved in. Us kids would go to the pond and sit for hours waiting to be able to spot a beaver. The beaver pond was a place of quiet reflection even for a bunch of kids. One day when we went to the pond, someone had broke the dam draining the pond and they shot all the beaver and just left them lay. I was probably eight years old at the time, but I will never forget how devastating it was to see the carnage. Who ever did it left the dead beaver where they dropped. It was a horrible waste of life and a terrible blow to the land. I ran home crying. My mom was in a rage. The game warden was called, but no one was ever caught and punished for it. If I ever have a piece of property that was conducive for beavers, I would not hesitate in having them as neighbors. There are many things that can be done to protect from flooding and chewing and beavers are actually very good neighbors. They draw in other wild life and make water downstream much cleaner.

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