Mammals
There are three types of aquatic mammals that can be found in the waters of the Colorado River. The largest of these is the beaver, which because of the swift currents and the size of the Colorado, cannot build dams on the river as it does on smaller streams. Beavers live in dens along the banks of the Colorado.
The muskrat, a much smaller rodent than the beaver, is also a resident. It also makes dens along the river bed. The river otter, which hunts for fish, crayfish, frogs and other creatures, is best described as semi-aquatic, equally comfortable in the water or on land.
Fish
There are several types of fish that live in the Colorado River. Smallmouth and largemouth bass can be found there as can walleyes, striped bass, channel catfish, crappies, rainbow trout and bluegill. Some of the native species include different kinds of carp, suckers and minnows. The Colorado pikeminnow, the flannelmouth sucker, and the bonytail chub are among these fish. The pikeminnow is capable of growing as long as 6 feet and can attain weights of over 100 pounds, making it one of the river's largest denizens.
Reptiles and amphibians
The western painted turtle is a reptile that lives in the Colorado River system. This turtle is easily identified by the reddish and orange colors on the bottom of its shell and the yellowish lines that are on its legs. Amphibian species found in the river and along its shores include the Arizona tiger salamander, which can live twenty years and the red spotted toad, which spends the beginning of its life in the water. The canyon tree frog, the Rocky Mountain toad, and the western spadefoot toad also can be found in the Colorado River during their larval stage.
