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.
A narrow tail distinguishes the muskrat from the beaver, which may live in the same locality.
The MUSKRAT is frequently active in daylight hours. It lives in the same environment as the beaver, but in the park has a much more limited distribution and is confined to lower elevations. It builds lodges, too; they are much smaller than those of the beaver, and are largely composed of mud and plant material. The lodge serves as a secondary food source in the winter, and many muskrat houses are practically eaten away by spring. Unlike the beaver, a strict vegetarian, the muskrat eats fish, insects, and any birds it can catch, as well as plant food. This animal has not acquired the ability to build dams, but does make rafts of sticks and twigs. When seen closely, a muskrat is easily distinguished from a beaver, for it is smaller and has a slender, vertically flattened tail, quite unlike that of the beaver.
Probably everyone recognizes the PORCUPINE. It is a large, short-legged rodent, rather clumsy of behavior, and usually seen either sleeping or leisurely chewing the bark of a tree. The porcupine survives, despite its sluggish behavior, because of the protection afforded by some 30,000 quills in its pelage. Although it cannot “throw” these quills, they are very loosely attached, and when the tail is vigorously thrashed about it is inevitable that some of the quills become detached and fall away. The unlucky recipient of such a slap of the tail will be convinced that the quills were thrown, although the effective embedding of quills is done by direct contact.
The MOUNTAIN COTTONTAIL is often seen in the lower forests. Despite heavy predation by many natural enemies, the cottontail manages to maintain itself because of its high birth rate. One mother may produce a total of 25 young in the 4 or 5 litters born during the year. It is fairly small, grayish-brown in color, with rather short ears and a conspicuous cottony tail resembling a powder puff. It lives in underground burrows and retains the same color winter and summer.
The SNOWSHOE HARE nests on the surface of the ground. Its fur changes from grayish-brown in summer to white in winter. A denizen of the spruce-fir and lodgepole pine forests and of the tundra, it hops about the snow on its huge, furry, “snowshoe” feet, apparently finding the severe winters of the high country no great hardship. It is not common in the park, and therefore is not often seen.
Porcupine.