Of the 34 mammal species found along the Colorado River corridor, 15 are rodents and eight are bats. Of the rodents, river otters may have disappeared from the park in the last decade and muskrats are extremely rare. However, an increase in the population size and distribution of beavers has occurred seen since the construction of Glen Canyon Dam. Beavers cut willows, cottonwoods, and shrubs for food, and can significantly affect the riparian vegetation. Other rodents, such as antelope squirrels and pocket mice, are mostly omnivorous, using many different vegetation types. Grand Canyon bats typically roost in desert uplands, but forage on the abundance of insects along the river and its tributaries.
In addition to bats, coyotes, ringtails, and spotted skunks are the most numerous riparian predators. They prey on invertebrates, rodents, and reptiles. Raccoon, weasel, bobcat, gray fox, and mountain lion are also present, but are much more rare. Mule deer and desert bighorn sheep are the ungulates that frequent the river corridor. Since the removal of 500 ferral burros in the early 1980's, bighorn sheep numbers have rebounded. Mule deer are generally not permanent residents along the river, but travel down from the rim when food and water resources there become scarce.
The mammalian fauna in the woodland scrub community consists of 50 species, mostly rodents and bats. Three of the five Park woodrat species live in the desert scrub community. Many generations of woodrats inhabit the same middens, which can serve as valuable indicators of past climatic conditions and associated vegetation. Numerous caves in the inner canyon provide roost sites for migratory and resident bats. Maternity colonies are especially prone to disturbance from human exploration, and greater efforts are needed to inventory park caves for bats and establish protective measures where necessary.
The conifer forests provide habitat for 52 mammal species. Porcupines, shrews, red squirrels, tassel eared Kaibab and Abert squirrels, black bear, mule deer, and elk are found at the park's higher elevations on the Kaibab Plateau.
Please remember that it is illegal to approach or feed wildlife in Grand Canyon National Park.