by Whit Gibbons

January 20, 2013

I received the following questions about beavers within the last month.

Q: I live in central Alabama and have seen two road-killed beavers near wetlands since Christmas. Are beavers moving into this region the way armadillos and coyotes have in recent years?

Q: Five years ago beavers lived along a small stream on my property near Columbia but then disappeared. Based on fresh cuttings, I deduce that they have returned. I have also some relatively large trees with bark missing around half the tree up to 3 feet above the ground, but the cut area is not fresh. Did beavers do this earlier? Do I need to worry about the three dogwood trees I just planted?

A: The geographic range for beavers extends from northern Florida and Mexico to Alaska and Newfoundland. One reason for the appearance of beavers in many areas in the southern part of their geographic range is that their mating season starts in winter. The babies are born in spring and early summer. For most animals, mating season finds them moving around as they seek mates. When large mammals live near highways, roadkill is a common by-product.

Beavers are the largest U.S. rodent and one of the most widespread North America mammals. Their numbers were drastically reduced during the period of overtrapping from colonial times to the 20th century, but small populations persisted throughout the country. Today, from 6 to 12 million are believed to exist in the wild. This may seem like a lot, but the comparative reduction in numbers is striking. One scientific estimate of beaver numbers in the 1700s was from 60 to 400 million individuals. Beavers now appear to be on the rise in many regions and are continually populating new areas. They are not, however, physically expanding their range like armadillos and coyotes. They are simply becoming more common where they already occur.

Beavers eat plants, including tree bark. Old, scarred areas on large trees often indicate a history of interaction between beaver and tree when the tree was much younger. The beaver stood on its hind legs and gnawed the bark of a small tree all the way to the ground. The beaver got a snack, but the tree survived and continued growing. Years later the chewed-off area of bark has gone no higher, but as the tree grows in diameter, so does the scar tissue. I have seen sweetgum trees more than two feet in diameter with large areas of bark removed by beavers years before.

Whether beavers will eat your trees depends on several variables, including how close the trees are to the water. A friend who lived on a lake told me with pride of her small beaver colony that she watched at dusk each day. Then one night the beavers cut down and carried away six boxwood shrubs she had planted the previous afternoon. The next night, as if to underscore their impertinence to their previously admiring audience, the beavers expertly felled a flowering pink dogwood tree 50 feet from shore.

Beavers are an environmental conundrum, a mix of positive and negative traits (at least from a human perspective). They are cute and charming up close. Tame ones can safely be allowed to eat out of your hand. A family of beavers in a lake can delight people who enjoy observing wild animals. They promise a rewarding wildlife experience and are a fine opportunity for parents to show teenagers what the word "industrious" means. But they can also destroy trees and shrubs, eat treated wood (such as that decks are built of) and flood areas you want to keep dry.

Cute and entertaining, yet potentially destructive, beavers are a good example of the complexity inherent in environmental preservation, with no simple solution as to how to handle the issue. A range of responses are available for dealing with nuisance wildlife. Which solution people choose will depend in part on their environmental conscience.

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