Sawtooth National Forest is home to over 243 bird species, 78 mammals, 28 reptiles and amphibians, and 29 fish. Invasive zebra and quagga mussels are potential threats to the forest's aquatic ecosystems because they can spread rapidly and cover large surface areas, including human structures, thus altering ecosystems, removing native mussels and threatening native fish. Wolves were controversially reintroduced to the SNRA in the mid-1990s to restore the ecosystem stability that they provide as top predators. This included managing high elk populations, which had inhibited new vegetation growth. Opponents to the reintroduction included hunters concerned that wolves would inhibit their ability to hunt the highest number of game species possible, ranchers concerned for the welfare of their animals, and land developers concerned that a species listed under the Endangered Species Act may restrict what they can do to their land.