There are now many creatures more numerous in captivity than in the wild, thanks to humans' relentless appropriation of the earth. Some, like the Bactrian camel, are being dragged into domestication. Tiger habitat is vanishing around the globe, but the tiger's numbers are booming, largely because of its popularity as an "exotic pet." (The World Wildlife Federation's estimate of 5,000 captive tigers is for the U.S. alone.) Captive red wolves and black-footed ferrets, on the other hand, are in breeding programs and are eventually returned to the wild. It worked for the California condor. In 1987, it was extinct in the wild, but there are now more condors in the wild than in breeding facilities.