There are approximately 75 species of mammals, 200 species of birds, 15 species of reptiles and 10 species of amphibians in the Lake Roosevelt area.

Large mammals include black bear, elk, mountain lion, whitetail deer, mule deer, and moose. California Bighorn Sheep were recently introduced to the area. Smaller mammals include: beaver, river otter, muskrat, mink, badger, raccoon, skunk, bobcat, coyote, red fox, porcupine, cottontail rabbits, ground squirrels, chipmunks, yellow-bellied marmot, pika, bats, gophers, rats, and deer and house mice.

Birds found in the watershed include raptors such as: osprey, golden eagle, bald eagle, prairie falcon, red-tailed hawk, northern harrier, and American kestrel. Passerines include swallows, finches, jays, chickadees, kinglets, ravens, magpies, robins, sparrows, blackbirds, and juncos. Water birds include: mallards, pintails, teal, goldeneyes, redhead canvasback, western grebe, coot, lesser scaup, common merganser, common loon, and Canada geese. Shorebirds include: plovers, northern killdeer, spotted sandpiper, gulls, snipe, common grebes and yellowlegs. Grassland birds include: western sage grouse, Columbia sharp-tailed grouse, mourning dove, blue grouse, band-tailed pigeon, pheasant and turkey.

Lake Roosevelt watershed reptiles and amphibians include: sage brush lizard, western rattlesnake, gopher or bull snake, western terrestrial garter snake, bullfrog, western toad and various salamanders.

Native species of fish in the area include: kokanee, rainbow trout, bull trout, white sturgeon, burbot, lake whitefish, minnow, sculpin and sucker species. Introduced species include: brook trout, brown trout, walleye, yellow perch, largemouth bass, smallmouth bass, black crappie, white crappie, sunfish and yellow bullhead.

Some of the species found around Lake Roosevelt’s watershed are endangered, these include: peregrine falcons, gray wolf, woodland caribou, bald eagles, grizzly bear, bull trout and Canada lynx.

There are also many species whose decline is a matter of concern, some of these include: ferruginous hawk, Canada floater, Columbia sharp tailed grouse, Columbia spotted frog, loggerhead shrike northern goshawk, bull trout, and white sturgeon.