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Blane Klemek column: Beavers are remarkable rodents

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Blane Klemek column: Beavers are remarkable rodents
Bemidji Minnesota P.O. Box 455 56619

I read with interest a recent Internet article about a beaver dam so large that it's visible from outer space.

Discovered by a Canadian ecologist in Wood Buffalo National Park, Alberta, the dam is estimated at about 850 meters long. Think about that. A beaver dam longer than the length of an 80-acre field -- more than half a mile in total length!

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The article described the dam as being very old, but still growing. Probably begun in the 1970s, successive generations of beavers have been working on the dam-building project for 40 years or more. A park spokesman described the dam as supporting significant vegetation growing on it, suggesting that the dam has been there for a long time.

Indeed, the story of the gigantic Alberta beaver dam reminds me of a familiar dam found in a similar, flat marshland environment, although located much further south and closer to home. As well, like the people quoted in the article, I am as fascinated about this northern Minnesota beaver dam as they are about their Alberta dam.

The beaver dam that I've come to know is located on a State Wildlife Management Area in Kittson County. It most definitely rivals the Alberta dam. In fact, it could even be longer (perhaps during my next trip up north, I'll take a GPS and measure it). Holding water from draining out of two distinct wetlands totaling about 15 acres, the old, sinewy dam is wide, high and vegetated. Willows, alders and poplar trees grow freely on most segments of the dam.

I've often inched my way along the top of this dam, working to keep my footing, careful not to misstep and fall into the deep ponds. While exploring the wild tangles of brushland and forest that the dam weaves through, I can't help thinking about the amazing animals that are responsible for constructing the massive dam. It always strikes me as nearly inconceivable that animals without tools, trucks and trackhoes can perform such incredible feats.

The beaver is the largest rodent in North America, and the third-largest rodent in the world. Adults average 35 pounds with some reaching as much as 65 pounds. Specimens of 90 pounds have also been found. Beavers can reach 4 to 5 feet in length from nose to the tip of their tail. Prehistoric beavers were almost as large as today's bears. Imagine the dams and lodges animals of that size would have constructed. One can easily imagine lakes, not ponds, being created by such creatures.

Long-lived for rodents, beavers can reach 20 years of age. They tend to mate for life. Kits remain with their parents for two years, until they disperse to locate their own mates and territories. One litter per year of two to four kits is born to a mated pair. So many marvelous adaptations help make beavers perfectly suited to an aquatic lifestyle. Powerful hind legs with flipper-like webbed feet propel them through the water with ease. Nostrils can be closed to keep water out. And clawed toes help assist digging and gripping sticks.

Beavers have extremely dense fur that repels water and keeps them warm in frigid conditions. Their massive chisel-like incisors, imbedded in equally massive skulls where powerful muscles attach to supporting jaws, provides beavers with the necessary means to cut through wood. And the beaver's broad and flat tails, used as both a rudder for swimming and for support when standing, is also used as a warning signal. A loud slap on the surface of the water warns other beavers in the pond that danger lurks nearby.

Aside from the impressive dams beavers construct to hold the water they require to survive, the lodges, too, are unique and elaborate in design. The inside chamber, which may be as wide as 8 feet and as high as 3 feet, is lined with soft vegetative materials like grass and woodchips. Depending also on the structure's design, the entrances may differ as well. Some entrances are bored vertically through the floor of the lodge, while other lodges are entered through gradually sloped entrance holes.

Beavers are especially active in the autumn as they prepare for the long, cold winter. Branches and sections of felled trees are transported near their lodge where they are stored underwater and called food rafts. Beavers cache these sub-surface food items for consuming throughout the winter months. When a meal is needed, the beaver simply exits the lodge, swims below the ice to the food raft, and carries back with it something to eat inside the warm and cozy lodge. It is the nutritious bark of the aspen tree that is among their favorite foods.

Though sometimes viewed as pests because of the problems they can create for people, beaver ponds provide many benefits for other species of wildlife. Flooded trees often die and subsequently become excellent cavity trees for wood ducks and other cavity-using wildlife.

River otter, mink, turtles, amphibians, aquatic invertebrates, fishes and many species of birds, such as belted kingfishers, great blue herons and scores of songbirds, shorebirds and waterfowl, use beaver ponds and the associated habitats, too.

Sometimes, because of sedimentation, diminishing timber resources or hydrologic changes, beavers abandon their ponds. These old and deserted ponds often become lush meadows that provide yet another valuable resource for a whole new assemblage of flora and fauna.

Beavers, with all their remarkable engineering abilities, not to mention their contributions to the environment and benefits to other species of wildlife, provide us plenty of reasons to get out and enjoy the great outdoors.

Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at bklemek@yahoo.com.

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