A Beaver Balance
Image © Janet and Phil, creativecommons.org
By Scott Meister, Natural Resources
Next to humans, no other creature has the amazing determination and capacity to change its surroundings more than the beaver.
Beavers are North America’s largest rodents, but they’re also members of a small group of semiaquatic mammals that spend a large part of their time in the water. Beavers' short, wide legs, webbed hind feet and rudderlike tails make them far more adept at traveling through water than over land. Clear eyelids and an ability to seal their ears and noses allow them to function even when completely submerged — up to 15 minutes at a time thanks in part to their large lungs. To protect their skin against this harsh, wet environment, they produce a waterproof oil they regularly spread over their fur with the help of split nails on their front paws called “grooming claws.”
American beaver © James Beissel
The beaver’s fur was, of course, almost its undoing. From the early 1600s until the mid-1800s, Europeans’ desire for its silky underfur drove trappers across North America. The beaver, some would argue, was perhaps the number one catalyst for Europeans’ westward exploration. Fortunately, conservation efforts that began in the late 19th century saved the animal from extinction.
As water-friendly herbivores, beavers enjoy the soft shoots and roots of aquatic plants, such as sedges, cattails and rushes, but also eat fresh bark and tender stems from young trees that grow on land. Fast-growing trees are especially suited to the beaver’s lifestyle. Willows, for instance, sprout in dense clumps near rivers and wetlands. Because beavers do not hibernate, they work on these clumps throughout fall so they have enough supple stems to store in their underwater food caches to sustain them through winter. Interestingly, this heavy foraging may initiate a defense mechanism in willows that causes them to resprout more robustly the following spring, making them a renewable food source.
Though not very tall, beaver dams can create large pools called “impoundments,” which benefit other wildlife as well.
To better access favorite terrestrial food sources, beavers build their famous dams, which are usually comprised of trees, mud and weeds. The pond, or “impoundment,” that forms upstream of the dam floods the surrounding area, giving the animals easy passage to future meals. But dams also illustrate the beaver’s role as a “good citizen” in the natural neighborhood. Migrating ducks and other birds use beaver-created wetlands to reach underwater plants and invertebrates, and in fall the area attracts frogs, toads and turtles looking for places where they can bury themselves in the sediment to hibernate through winter. One such dam with great wildlife viewing opportunities is at James “Pate” Philip State Park in Bartlett near the pedestrian bridge at Brewster Creek by the visitor center.
One lodge, which can be over 5 feet tall and 40 feet wide, can house a family of up to eight beavers. © John H. Ghent, USDA Forest Service, Bugwood.org
Another of the beaver’s construction feats is the lodge. Beavers build these dome-shaped structures — some rising 5 feet above the water’s surface — often along shorelines upstream of their dams. The ability of a dam to maintain elevated water levels provides a key safety feature because it keeps the underwater entrances to a lodge hidden from predators. Inside the lodge, the animals have dry shelter, lots of air and space to have and raise their young. Although beavers are mainly nocturnal and rarely seen, visitors can spot their homes and other handiwork in many forest preserves.
The beaver’s engineering skills can be fascinating, but its accomplishments are not always appreciated. When local waterways swell with melting snow and spring rains, the sound of running water triggers a call-to-action by beavers to expand and reinforce their dams. This can cause water to spill beyond the banks of a stream or edge of a wetland and lead to public safety concerns or damage to buildings or landscaping. It’s not difficult to see why many people believe that beavers are nothing more than a nuisance. To coexist in such a developed landscape as DuPage County, a delicate balance must be struck between humans and beavers.
Beavers’ ever-growing incisors have chiseled ends, which are perfect for stripping bark to reach the edible layers below and for felling trees for building materials.
Fortunately, there are a variety of actions people can take to protect against beaver-related damage. Homeowners can protect desirable trees by wrapping the bases with wire-mesh fencing or hardware cloth. When a dam causes safety concerns, professionals can install pipes to move water around or through it. Removing beavers from an area to solve a conflict, though, is not typically effective. Beavers live in family groups where young kits often remain with their parents for two years while learning survival skills. Removing adults can leave kits in a vulnerable predicament, and trying to remove the entire family can be extremely difficult. Besides, given the abundance of beavers and the distance young disperse from their natal area, a new family of beavers will quickly move into any suitable habitat. In the forest preserves, unless beavers are causing flooding on private property, they are usually left alone.
Beavers are not only fun to observe but also important to our ecosystems, and our ability to live in harmony with these creatures speaks to our success in providing habitat for and coexisting with wildlife in our urban landscape.
Source: The Conservationist