The diversity of the flora and fauna in the Pinaleños make them an especially notable range. Trees that grow there include: Douglas fir, Engelmann spruce, quaking aspen, Ponderosa pine, silverleaf oaks (south-facing slopes), box elder, and bigtooth maple. Frequently seen animals include mule deer, Coue's white tail deer, hawks, and black bear. The Mount Graham red squirrel was once considered to be extinct, but was rediscovered in the 1970s and as of June 3, 1987, is officially listed as endangered. For a comprehensive list of the flora and fauna of these biodiverse mountains see the University of Arizona's Mount Graham Biology Program.