The beaver is the largest rodent in North America. One of the most notable traits of this species, however, is not its size but its ability to transform its environment to suit itself. Most animals have at least some effect on the environment around them. Spiders weave webs to catch passing insects. Woodpeckers chip cavities in the trunks of trees to build their nests. But few animals (except for humans) have as much of an impact on their environment as the beaver does. In fact, a single family of beavers can in a matter of weeks turn a small, rushing stream into acres of deep, still, interconnected ponds, creating a wetland that would otherwise not exist.
Besides humans, beavers are the only species on earth that know how to construct dams. Scientists often refer to beavers as the engineers of the animal world. But unlike humans, who must be taught how to design and build dams, beavers know instinctively how to interweave sticks to create a strong and durable structure and how to seal a dam with mud to make it impermeable to water. They are born knowing how, just as birds know how to sing songs or build nests without ever having done so.
A beaver's work is critical to the survival of its family. The deep ponds that beaver dams create offer refuge from predators and from the freezing temperatures of winter. As long as a beaver dam is tall enough and the resulting pond deep enough, a family of beavers will have underwater access to food throughout the winter.
Perhaps more importantly, beaver dams and ponds provide habitat that wouldn't otherwise exist for many other species. Ducks, geese, herons, turtles, and frogs are just a few of the species that benefit from the deep and wide waterways that beavers create. Unfortunately, this is where the dam-building accomplishments of beavers and humans diverge. While small ponds constructed by humans can be just as beneficial as a beaver pond, huge dams, including the Hoover Dam pictured in the video, serve more often to flood vital habitat than to create it. Dams as large as this create incredibly deep reservoirs that lack the diversity and richness of the ecosystems created by beavers.
