Beavers are often called “nature’s engineers” for good reason. With nothing but their teeth and paws, they turn streams into ponds and raise sturdy lodges that stay warm and dry at the pond’s center. They reshape landscapes more than any other animal except humans, and some dams are so large they are visible from space; one in Canada stretches around 850 meters (about 0.53 miles). What fascinates observers isn’t just what they build, but why they build and how these rodents pull off feats that rival human engineering.

The North American beaver (Castor canadensis) is the world’s second-largest rodent, often weighing 20 kilograms (about 44 pounds). Built for water, beavers have webbed hind feet for swimming, dense waterproof fur, and a flat, paddle-like tail for steering in water and for balance on land. Their ever-growing front teeth are fortified with iron, which gives them an orange tint and the strength to chisel wood. Beavers typically live as a mated pair with their kits (newborns) and yearlings (last year’s offspring), and the whole family helps gather branches and repair structures; think of it as a small, well-run construction crew.