The Busy Beaver
Here in Illinois beavers aren't appreciated as much as they are out in the western U.S. In the parched, desert-like mountains and plains of the western U.S., beavers create aquatic habitats that bring in a multitude of plants and animals, creating biodiversity where there once was none. Their dams also create wetlands where floodwaters can slowly soak into the ground and pollutants and toxins can get filtered out. Before settlement of this area, most of Chicagoland was wet and marshy. But here in the heavily populated region of northeast Illinois, too much water isn't a good thing especially when it ends up in our basements.
However, it's easy to appreciate North American beavers, Castor canadensis, for what they can accomplish - they are master engineers. Scientists have found that the sound of running water triggers a beaver's instinct to build a dam. The calmer, deeper water that forms behind a dam provides a perfect place to build the beaver's home, or lodge. With an underwater entrance and above water living area, a lodge affords protection from predators and the weather. In the autumn, beaver families of up to six individuals chew down and drag saplings into the pond which they stash underwater. Even if the pond freezes over, their underwater larder is full of food to eat throughout the winter. Beavers eat the soft, green growing portion of a tree found under the bark, called cambium. They also eat aquatic plant roots, marsh grasses, and sometimes berries and fruits.
With their nocturnal nature, we don't see beavers very often. They are skittish and will slap the surface of the water with their broad flattened tail if you get too close. Each night they are busy building and repairing, cutting down and collecting trees under the cover of darkness. The easiest way to know they are around is the sight of a dam or lodge, the telltale chew marks they leave on trees or, if you are lucky, a webbed footprint in the mud. Beavers are big animals, with adults weighing anywhere from 40 to 90 pounds. (The muskrat, another common, but much smaller, aquatic mammal, builds its lodge of cattails and other vegetation, not trees).
Believe it or not, beavers were once on the verge of extinction. In the early 1800s, their dense waterproof fur was highly prized by settlers in the US and especially in Europe. Trapping along with draining of land for agriculture use reduced their numbers quickly until by 1850 they were no longer considered a viable part of the fur trade. Even today, after reintroduction efforts, their population is a fraction of what it once was – about five percent of the pre-European numbers. But these animal architects are making a comeback; as long as they can find a stream with a good food source, like maples and willows, they will continue to design and build.
