The majestic Sierra Nevada bighorn sheep is the eastern Sierra Nevada’s only wild ovine mountaineer. Learning to leap from crag to crag in early lambhood, these bighorns develop quickly into keen-eyed, strong-limbed and extremely agile creatures always on the move to escape mountain lions and find food among steep, rocky slopes. Although they once populated the High Sierra by the thousands, settlement of the West brought domestic sheep and other threats to the bighorn’s habitat, and the species is thought to have been imperiled since the Gold Rush.

The Sierra Nevada bighorn sheep was the first species to be listed under the Endangered Species Act in the 21st century, and rightly so: In fact, listing should have happened much sooner. The species began its decline back in the mid-1800s upon the influx of settlers and domestic sheep to the Sierra Nevada, and by 1995 the total population numbered few more than 100 individuals. Primarily because of diseases introduced by sheep grazing in their habitat, Sierra Nevada bighorns experienced a series of dramatic declines in the latter half of the 20th century.

Thanks to Endangered Species Act listing, the bighorn has come back from the brink of extinction, and its population is slowly on the rise. Three subpopulations have been reintroduced to areas where they were lost; the U.S. Forest Service has acted to reduce the impact of domestic sheep on bighorn populations; and in 2008, a Sierra Nevada bighorn recovery plan finally published. But although the Endangered Species Act requires critical habitat to be designated upon a species’ listing, the U.S. Fish and Wildlife Service was slow to put federal habitat protections in place. In 2005, the Center sued the Service to force critical habitat designation, and in August 2008, the Service designated a total of more than 400,000 acres. Still, the agency failed to adequately protect the bighorn from potentially dangerous disease transmission — so the Center warned of another suit in 2009.