National Geographic : 2013 Oct
Modern arks 153 critically endangered; no more than 150 are estimated to exist in the wild. Not long ago the zoo announced it was going to try to breed half the species on the list of the world’s 25 most endangered turtles. It has appealed to other zoos to take on the remaining half. “This can’t be a missed opportunity,” Breheny says. “Even if you’re a small zoo, you can house one species or several species of turtles and re- ally make a difference.” On the other side of the country, at the San Diego Zoo Institute for Conservation Research, Marlys Houck pulls a box of small plastic vi- als from a vat of liquid nitrogen. To protect her hands from the cold—the temperature inside the vat is minus 320°F—she’s wearing what look like heavy-duty oven mitts. The vials are arranged upright, in little slots. Houck locates the two she wants and places them on a steel table. “There they are,” she says. Inside the vials is much of what’s left of the po‘ouli, a chunky bird with a sweet black face and a light chest that lived on Maui. The po‘ouli probably went extinct a year or two after the San Diego Zoo and the U.S. Fish and Wildlife Service made a last-ditch effort to save it, in 2004. At that point a mere three individuals were thought to exist, and the idea was to capture all of them and try to breed them. But only one bird—a male— allowed himself to be netted. When he died, two months later, his body was immediately sent to the San Diego Zoo. It was Thanksgiving weekend, and Houck rushed to the institute to harvest still living cells from the carcass. “ This is our last chance,” she remembers thinking. “This is the dodo.” She succeeded in culturing some of the cells from the bird’s eye, and the results of that effort now make up the contents of the vials. (The po‘ouli’s skin is now at the Smithsonian.) Houck doesn’t want the cells to get so warm that they are damaged, so after about a minute, she places the vials back in the box and returns them to the vat. The liquid nitrogen gives off a misty, ghostlike vapor. Along with thousands of other identical- looking vials, the tubes of po‘ouli cells represent what might be described as a beyond-the-last- ditch conservation effort: the Frozen Zoo. Nearly a thousand species are represented in the Frozen Zoo, which occupies a single room on the insti- tute’s ground floor. For now, at least, all but one of the species in deep freeze still have flesh-and-blood members. But it seems safe to predict that in the coming years, more and more will go the way of the po‘ouli. Many of the animals in the “zoo” are highly endangered; these include the Sumatran orangutan, the Amur leopard, and the puaiohi, a songbird from Kauai. As I watch Houck put away the little vials, I wonder about a future in which what counts as conservation all too often involves liquid nitrogen. Though frogs and toads enjoy the dubious distinction of belonging to the world’s most endangered group, it’s worth noting that extinction rates among many other classes are approaching amphibian levels: It’s estimated that a third of all reef-forming corals, a quarter of all mammals, a fifth of all reptiles, and a sixth of all birds are headed toward oblivion. “I think there are going to be more and more species where the only living material left is go- ing to be cells in the Frozen Zoo,” Oliver Ryder, the institute’s director of genetics, tells me. As it happens, one such species, or really, in this case, subspecies—the northern white rhino—can be found just a few hundred yards from Ryder’s office. Native to central Africa, the northern white rhino is down to its last seven individu- als, and its extinction is at this point considered inevitable. Two of the seven—Nola, a female, and Angalifu, a male—live at the San Diego Zoo Safari Park, and when I leave the institute to go visit them, I find them basking in the late after- noon sun. The animals are both nearing 40 and too old to breed. But after they die, they will, in a manner of speaking, live on—one last hope, suspended in a frozen cloud. j Zoos may have to rethink their mission. Why devote resources to species that are doing fine?