Leave it to beaver: Hydro-engineers alter water flow, landscaping

One North American rodent has had more influence on politics, economics, international relations and nation-building than any other of its kind.

Its work ethic is second to none. Its hydro-engineering skills match those of the Army Corps of Engineers. As a swimmer, it is in the league of Olympians. It can outsmart any landowner who tries to evict him.

Who is this super-creature? It's the American beaver.

The beaver has a storied history, beginning with its Ice Age ancestors and its prominence in Native American culture, legend and folklore. The beaver's history continued through the heyday of the 16th century fur trade, to centuries of over-trapping and near-extinction. As with many of the natural resources in the New World, the beaver - valued for its pelt and scent glands - was over harvested. Beavers were extirpated from most of Illinois by the second half of the 19th century.

Legislation in the early part of the 20th century, combined with improved wildlife management and reintroduction programs, led to population recovery and rebound.

Today beavers can be spotted throughout the suburbs. Bulky yet sleek in water, powerful and agile on land, they are masters of waterways and wetlands. When swimming, only their head is visible, leaving a silent wake on the still surface of the water. If frightened, a slap of their broad, flat tail on the water announces danger to their aquatic comrades. Other telltale signs of beaver activity today are, of course, gnawed and felled trees on shorelines.

A year-round, semiaquatic lifestyle presents significant challenges. Over time, the American beaver has developed numerous adaptations that lend themselves to success in this taxing environment. To protect its excellent hearing, there are valvular flaps that keep water out of the inner ear while the beaver is swimming. The nose also has flaps that close underwater, protecting another one of the beaver's acute senses. A beaver's lips close behind its teeth, allowing them to carry sticks while swimming.

And, beavers wear goggles underwater - figuratively speaking. More accurately, their eyes have three eyelids, providing extra insurance against getting poked by sticks and twigs. Oil glands are used for waterproofing the double-layered coat. A special double-pronged claw is used to groom the coat and remove burs.

And finally, the beaver's broad tail is used both as a rudder in water and a stabilizer on land.

The beaver's skills and adaptations make it one of the coolest creatures of streams and waterways. But a beaver sighting in suburbia may or may not bring joy to the eye of the beholder. Why? Because they're so darn good at what they do. And what they do is alter the landscape and eat our landscaping in the process.

Beavers are infamous for carrying out intricate hydro-engineering projects that change the hydrology of waterways and wetlands and farms and housing developments. The motive for building dams is to create a comfy habitat, safe from predators, with a year round food source. Food is cached in the dam where a beaver family can have meals uninterrupted by the threat of coyotes or other predators crashing the party. A beaver dam also insures safe underwater ingress and egress to bank dens and lodges. The dam backs up a creek or stream, causing the water to rise and pool up behind the dam. The deep water will not freeze, and the beavers come and go as they please throughout the coldest months of the year.

So how does this engineer sans blueprints create its elaborate construction projects? The beaver begins by selecting a narrow spot on a creek where a logjam or debris have already begun to constrict the water. Then the logging operation begins. Like a forester "walking timber," the beaver selects trees to fell. In our neck of the woods, willows, cottonwoods and alders are favored for dam construction, but as many people with streamside landscaping know, just about any woody tree or shrub is fair game.

Lacking opposable thumbs and a chain saw, the beaver's formidable incisors are the tool of choice. The beaver uses those sharp incisors to chisel away at a tree while stabilizing himself with his broad, flat tail. He chisels and chips until he has created a notch in the trunk until the tree topples over. Contrary to rumors, however, the beaver cannot determine the direction of the fall. Many streamside trees lean toward the water, however, and thus fall into or across the creek. If not, the beaver uses its mouth and dexterous front paws to haul the construction timbers and places them where he wants them.

Once he secures large trunks and branches to make a solid framework for the dam, the beaver selects medium sized sticks and to provide strength and stability to the structure. He slaps mud throughout for good measure. He will tweak and adjust until there is not even a trickle of water spilling downstream. The resulting dam is amazingly sound, as anyone who has tried to break apart such a structure knows.

Beaver dams are often confused with lodges. Both structures are built with logs, sticks and mud but each serves a different purpose. The dam stretches across the stream to halt the flow of water and alter the habitat. The dome-shaped lodge is situated along the shore and provides shelter.

Beavers construct a third type of structure, however, which is hard to spot. Dens are excavated in stream banks for shelter. These sites are actually preferable to lodges. Only if stream banks are unsuitable for den construction will beavers build a lodge.

While the beavers' talents and skills may be impressive, they are not always welcome. To the dismay of farmers whose fields are flooded and homeowners whose landscaping is reduced to stumps, beaver activity is destructive and expensive to repair. In many cases, the beavers' engineering success is its very downfall, as "nuisance" beavers have to be removed.

Challenging these infamous civil engineers is not a simple matter. Sometimes farmers, homeowners and parks personnel march out to streams and culverts, armed with rakes and hoes to break up beaver dams. The poke and they prod, they sweat and they toil, and at last they break the dam. Water runs free again. But these efforts are in vain.

"Beavers can't stand the sound of running water," a wildlife specialist told me. Shall we say it sets their teeth on edge? A beaver is likely nearby, watching, listening and waiting while the humans breach the dam. When night comes and the beaver hears that current running, the repair crew gets to work, and by morning, the dam is rebuilt.

The American beaver is one tenacious and superbly talented critter. It is an engineering wonder of the animal world. Although unappreciated by people who have sustained damage from beaver activity, these indefatigable aquatic engineers are worthy of admiration - and are welcome in natural areas where they are integral in the ever-changing landscape.

• Valerie Blaine is a naturalist with the Forest Preserve District of Kane County. You may reach her at blainevalerie@kaneforest.com.