Once driven nearly to extinction by rampant fur trapping and forest clearing, beavers are colonizing large swaths of North America where people don't remember seeing them. Since Massachusetts banned lethal leg-hold traps in 1996, the state's beaver population has tripled, to 70,000. North Carolina may have half a million, Manitoba twice as many. From Maine to Alaska, California to the Carolinas, the beaver's numbers are exploding.
So too are complaints from property owners, many of them ardent environmentalists who like beavers in principle but not necessarily in their backyards. They know that beavers help create wetlands, those ecologically vital landscapes that Environmental Protection Agency administrator Michael Leavitt calls "nature's kidneys." But, like hiring Hell's Angels to work security, relying on the continent's chubbiest rodents to put your landscape in order is not always a good idea.
If you're standing in beaver territory, you had better be wearing hip boots. An ungainly waddler ashore, Castor canadensis spends 80% of its life in water, where it's as agile as a 50-lb. minnow. Dam building is its way of making the world a wetter, safer and more convenient place. Only humans alter their environment more drastically.
But humans aren't aquatic. Most of us, in fact, wish the world were dryer, not wetter, and flooding tops the list of human grievances against the beaver. By raising water levels, its unkempt but admirably watertight dams can flood basements, swamp sewer systems, spoil trout streams and even derail trains.
Complaint No. 2 is the beaver's maniacal devotion to felling trees, which provide it with food and building material. An adult can gnaw through a tree six inches in diameter in 15 minutes. In the Southeast, beavers cause millions of dollars of damage to timber forests every year. In 1999 a squad of bucktoothed renegades in Washington started toppling cherry trees along the Tidal Basin, putting at risk the annual Cherry Blossom Festival. (When the National Park Service relocated the colony to an undisclosed location, then Idaho Congresswoman Helen Chenoweth, a die-hard foe of reintroducing the wolf and grizzly in the West, demanded the Tidal Basin be declared "habitat critical to its well-being and survival" and the return of the beavers.)
Keeping beavers at bay isn't as simple as it was 40 or 50 years ago, when trapping was a popular hobby and wetlands were disdained as swamps. Most state wildlife agencies have since declared themselves out of the beaver-control business. If you're a property owner vexed by beavers, you'll probably have to pay for the remedy yourself provided you get the proper permits. Licensed commercial trappers charge several hundred dollars per animal, and a large pond can support dozens of them. Most communities frown on tearing up dams, dynamiting lodges or stocking beaver ponds with hungry alligators (a ploy tried in Mississippi without success in the late 1970s).
A more civilized approach is to install clandestine pipes known in the trade as Beaver Deceivers or Beaver Bafflers that lower a pond's level without disturbing the beaver dam, at least until the animals notice the pipe's intake and plug it. Another is coating tree trunks with a paint-and-sand mixture to deter gnawing. But these measures can cost $1,000 or more, and upkeep can be a headache.
The most enlightened perspective at least if you're a beaver is to acknowledge that beavers occupied North America's floodplains long before people started building McMansions near creeks and streams. Even many colonial farms were sited on the fertile bottomland of a drained beaver wetland, according to John Hadidian, director of urban wildlife for the Humane Society of the United States in Gaithersburg, Md. "From the point of view of the beaver," says Bruce Baker of the U.S. Geological Survey in Fort Collins, Colo., "there are no problem beaver. There are just problem people."