Many times at Wolf Ridge Environmental Learning Center in Finland, Minn., and not far from Lake Superior, I have enjoyed, with student groups, observing beavers in their partly wooded stream valley natural habitat.
We watched them swim with tree branches in their mouths, using their flat tails as rudders and webbed feet to move swiftly. We also listened to their tails slap the water as an alarm. We recorded their nighttime activities, too, with trail cameras.
The beaver is nature’s original conservationist and wildlife manager. The beaver dams that create ponds support a greater variety and abundance of wildlife than any other ecosystem in the forest. Although beavers provide many positive environmental values, they can cause property damage by cutting valuable trees. Their dams often cause farm and road flooding. Historically, the trading of beaver pelts was the catalyst for the exploration and settlement of Canada and much of the northern U.S. from the 1500s to 1800s.
Quaking aspen bark, twigs and leaves are their favorite food, but other trees, ferns and aquatic plants like waterlilies are eaten, too. Lodges constructed with small tree trunks and branches are typically about 12 feet across and 5 feet above water level, with two underwater entrances. The colony residing within can be made up of an adult pair plus first- and second-year young. The young are born in May or June in litters of three or four. Beaver babies weigh less than a pound but will follow their mothers underwater before they are a day old.
Beavers live in every Minnesota county. They can weigh up to 90 pounds, with most adults about 40 to 50 pounds. The largest North American rodent, the beaver is adapted to an aquatic environment. As it goes under water, its nose and ear valves close, a special membrane acts as goggles to protect the eyes, and its lips close behind the front teeth, allowing branches to be carried by mouth without taking in water. A beaver can be submerged as long as 20 minutes.
Jim Gilbert’s observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.