Save for humans, there may not be another animal with as profound an influence on the land as a beaver. A family of these creatures can build a dam overnight, using locally available materials - sticks, stones, mud and reeds - to convert a river or stream into a wooded marshland. The thriving ecosystems inadvertently created by beavers support a vast web of wildlife, including fish, frogs, birds and mammals.
During a typical life span of about 12 years, a beaver may cut down thousands of trees - each felled in a matter of minutes - which are used for creating a network of dams, spaced every 500 or so feet along a stream, that can withstand all but the most violent floods. These dams, in turn, decrease siltation downstream by filtering out solid materials suspended in the water. By slowing down the flow of water, the dams also help to recharge aquifers.
Marshes reestablished along the Des Plaines River in northern Illinois, for example, owe their success to the labors of beavers and muskrats, claims hydrologist Donald Hey, who heads the restoration effort from the human end. As for the animal contingent, beavers get most of the glory, but lowly muskrats play a key supporting role. They carve out small, circular patches - clearing about one-twentieth of an acre in a couple of days - within a solid stand of cattails, creating interior spaces for ducks and other wildlife to inhabit. "Once muskrats opened up these areas, the yellow-headed blackbird, an endangered species in this state, moved back in," says Hey. "If you took the muskrats out of this environment, we wouldn't have yellow-headed blackbirds or the plant diversity we have."
Muskrats build cone-shaped "lodges" out of cattails and other marsh materials that rise above water level, providing a home for up to a dozen of their kin. The "roofs" of these structures serve as preening platforms, resting places, feeding stations, nesting foundations and latrines for mallard ducks, trumpeter swans and other birds.
Ecologically speaking, muskrats assume an important place in the food chain, providing the occasional meal for minks, wolves, foxes, owls, hawks, snapping turtles and other predators. But in this country, muskrat meat has yet to catch on as a food source for humans. That's probably a good thing, as it leaves more of these animals available to apply their unique skills as wetland architects and engineers.
More than half of the wetlands in the United States have been lost to human activities and as much as 90 percent of the wetlands in states such as California and Ohio have been wiped out.