The beaver—buck-toothedpaddle-tailed and famously industrious—has been reshaping freshwater landscapes for millions of years. With their iron-reinforced orange incisorsthese skilled rodents cut down trees and build dams that slow the flow of waterimprove its quality and create wetlands that support a remarkable diversity of life. Their sturdy lodgesmade of branches and mudhave underwater entrances that protect them from predators and keep their families safe.