One hundred years ago, the fleet-footed Sierra Nevada bighorn
sheep kept time to the mountains, moving upslope to summer
pastures in the spring, down slope to winter ranges in the fall
when blizzards beset the high Sierra. They roamed between
Olancha and Bridgeport, walking knife-edged ridges, dodging
mountain lions and avalanches, sleeping under a thick, warm
blanket of snow when temperatures plummeted to 10 below. Then,
in the course of a half century, they almost disappeared,
knocked from their high and lofty perches by disease, habitat
loss and other factors scientists are still trying to
understand. By 1999, there were just 100 of the sheep left in
the world. Their closest relatives, the Desert bighorn of the
Great Basin country and the Rocky Mountain bighorn, were
separated by huge swathes of land, making interbreeding
impossible. The Sierra bighorn was headed for extinction. But a
last minute push to save the sheep took hold and they landed in
the middle of the federal Endangered Species list, a design