There are almost 60 different species of mammals in the park. The most important species are the Gray Wolf and the Grizzly Bear.
The Gray Wolf was reintroduced into the park, because it was extinct in 1930 by hunters.
Other large mammals are the bison, black bear, elk, moose, mule deer, mountain goat, pronghorn, bighorn sheep and puma.
A lot of the visitors are going fishing in the big lakes for about 18 species of fish.