The beaver is well adapted to its water environment. The hindlegs are webbed for efficient swimming; the tail, broad and horizontally flattened, helps in underwater maneuvering. However, its swimming speed at the surface of the water is only about 2 miles per hour. Beaver can remain submerged for over 5 minutes; this ability helps in escaping enemies. [Illustration: The beaver is sometimes seen by alert observers in late afternoon or early morning.] Beaver dams are abundant in the park. Many typical examples can be seen in Horseshoe Park, Moraine Park, Glacier Basin, and Hidden Valley, and along the Colorado River. Nearly all of the park trails pass beaver workings. The dams are built of various materials in this region, but most commonly of mud, parts of aspens, and debris. They are started from the upstream side—usually on shallow creeks—and as the water level rises so does the dam. The beaver uses its front paws almost as hands. The load of mud or sticks sometimes is carried by being pressed against the chest as the animal walks on its hind feet to the top of the structure it is building. The dam is made to create a stabilized water level. This is essential for protection of the beaver’s island den—a lodge made of sticks and mud. The beaver house starts as a solid heap of debris, but the animal chews and digs out a couple of underwater tunnels, as well as one or more dome-shaped rooms with the floor a few inches above water level. In this dry retreat the beaver rests, sleeps, and rears its family. Few natural enemies can pursue it through the underwater entrances. Its food is chiefly aspen bark and twigs. A winter supply is stored under water during late summer. Because of its energy, skill, and persistence, the beaver has become a symbol of industriousness. It is also often credited with more intelligence than it probably possesses. Its apparent industry and resourcefulness are due more likely to inherited instincts than to reasoning. At any rate, this large rodent is surely one of the most interesting animals in the park. [Illustration: A narrow tail distinguishes the muskrat from the beaver, which may live in the same locality.]