Already there are species that are effectively extinct in nature, but live on in pens and cages, obsessively nurtured, studied and subtly–or if necessary, overtly–coaxed into that triumph of zoology, captive breeding. The American Zoo and Aquarium Association has drawn up “species survival plans” for breeding and conserving 92 endangered animals, from the majestic tiger to the humble Wyoming toad. The 750 Bali mynahs in captivity far outnumber the 30 still living in a Balinese national park. Przewalski’s horse, a Central Asian species, hasn’t been seen in the wild since 1968, but zoos have bred whole herds of them. Even “wild” populations of some large animals, such as rhinos and elephants, have to be so closely guarded and managed on their preserves that they might as well be in zoos.
The monks had it easier, because it’s enough to save one copy of a manuscript, but not just one oryx, or even two. Making more can require procedures as elaborate as the illustrations in the Book of Kells. There are only about 1,000 pandas in the world, but for years Shi Shi, a male on loan from China to the San Diego Zoo, held out for someone other than the resident female, Bai Yun. “She would solicit him, literally backing into him, and he would either growl or slap her or back away from her,” says Don Lindburg, who runs the zoo’s panda program. Artificial insemination was the solution–a tricky procedure with an animal that ovulates only once a year. The offspring, a female named Hua Mei, is the first panda bred in an American zoo to make it past infancy. The hope is that she won’t be the last–and that somewhere a male is gestating who will someday mate with her.
The species people most want to save are complex social animals, who aren’t about to forgo their mating rituals just because some bureaucrat puts them on an endangered list. There have been some successes over the years. In 1949, when the Bronx Zoo made a time capsule for its 50th anniversary, a curator dreamed that someday gorillas might be bred in captivity. By the time the capsule was opened this year, 43 gorillas had been born in the Bronx. But sometimes, even as the bells of extinction are about to toll, ethologists are still trying to figure out exactly how the creatures ever managed to propagate in the first place. Traditionally, keepers separated panda cubs from their mothers at about 6 months, so the females would come into estrus again more quickly. But some zoologists now believe that interferes with the development of adult social behavior, which explains why captive-bred pandas have such poor mating skills. Cheetahs, which once ranged as far east as India, are down to about 12,000 in the wild, almost all in southern Africa. They have, says San Diego Zoo’s director of conservation science Alan Dixson, a “prolonged and subtle” courtship behavior requiring lots of territory, which is only now being decoded, although the animals have been kept in captivity for millenniums. Meanwhile the number kept in zoos has dropped by half over the last 10 years as they died without reproducing. Responsible zookeepers won’t take them from the wild.
And it’s not enough just to breed the animal. Zoologists are fanatical about preserving genetic diversity, which is difficult enough in captivity; even in the wild, it becomes a problem when animal populations become scattered among “islands” of habitat with no chance to interbreed. As genetic diversity declines, congenital defects increase, along with the risk of devastating epidemics. Hence cloning, which has sometimes been suggested as the ultimate solution for endangered species, would be pointless, according to Dan Viederman, an expert on panda conservation. By definition, cloning contributes no new combinations to the gene pool. Some scientists, though, want to use cloning to bring back extinct species, such as the woolly mammoth. Larry Agenbroad, a paleontologist at Northern Arizona University, says that “top researchers from top labs” have contacted him about cloning a mammoth from a carcass he helped excavate in Siberia this fall. Many scientists think this is hopeless, pointless or both, but he sees it as a tremendous boon to conservation. “Can you imagine what having a small herd of mammoths would do for zoo revenues?” he says.
Of course, the thing about cloning, and zoo-based breeding programs in general, is that the ultimate goal of conservation biology is to return animals to nature, not breed them for exhibition. A century ago, bisons, which had been almost exterminated by hunting, were reintroduced to the prairie from the Bronx Zoo. But that worked only because the prairie was still there. It makes no sense to return pandas to China if the bamboo forests there have been cut down for farmland. Animals such as the panda, the gorilla or the California condor are important not just–or even primarily–for themselves, but as surrogates for their respective ecosystems, including all kinds of animals that never get put on postage stamps. “If you save the big animals without saving their habitat,” says Douglas Myers, executive director of the Zoological Society of San Diego, “you lose almost everything.”
It is easy to grow pessimistic. “You could say, ‘Well, the rain forests are going, most of the primates are going to become extinct’,’’ says Dixson. “But there’s no point in being depressed. I just think we have to fight on and do the best we can.” Very much like the monks in their scriptoria, in fact, desperately conserving for a future that they cannot quite imagine.
