Carnivores in Captivity: Size of range in wild may predict risk in zoo

The extent of a species’ home range can be used to forecast how well members of the species will adapt to captivity, according to a controversial new survey of troubled behavior in zoo animals.

“As far as I know, we’re the first to test species vulnerability to welfare problems in captivity,” says Ros Clubb of the University of Oxford in England. She spent 3 years examining carnivore-behavior studies from about 40 zoos. Animals with the biggest ranges, such as polar bears, tended to have the highest infant mortality and do a lot of repetitive pacing, report Clubb and her coauthor Georgia Mason.

The results highlight a nasty problem for conservationists, says Clubb. Animals that need a lot of land often prove the hardest to conserve in the wild, yet her results show they could also be the most vulnerable in captivity.

Zoos may need to learn new ways to care for these species, Clubb notes. She and Mason suggest an alternative in their report in the Oct. 2 Nature: “Zoos could stop housing wide-ranging carnivores and concentrate instead on species that respond better to being kept in captivity.”

Animal keepers have long recognized that some species, such as ring-tailed lemurs and snow leopards, adapt better to captivity than other species do. “Quite a few people have made suggestions about why,” Clubb says.

To test a possible link to home-range size, she and Mason considered 35 carnivores, including lions, cheetahs, brown and black bears, mink, brown hyenas, and arctic foxes. The researchers noted the minimum territory an animal covers in a year, according to published reports.

Then they reviewed publications from zoos and several mink and fox farms, mostly in Europe and the United States, on some 300 captive animals. Infant mortality in captivity, often the result of neglectful mothering, didn’t correlate with infant mortality in the wild or with typical adult weights but did tend to increase with size of the home range. Captive minks, for example, have lower infant mortality than lions do.

Clubb and Mason also studied repetitive, or stereotypic, pacing because it’s the most common tic reported in captive carnivores and one that all the species share. Animals that paced for large portions of the observation period tended to belong to large, wide-ranging species. Polar bears, for example, often develop severe pacing habits. The researchers note that in the wild, polar bears range over at least 1,200 square kilometers annually, an area about a million times greater than that of the typical enclosure. In contrast, brown bears, reported in ranges as small as a half-kilometer square, pace only half as much as polar bears do. Also, the Arctic fox covers less than a square kilometer, and the species ranks low in stereotypic pacing.

The report raises the hackles of some zoo professionals. “It’s very simplistic,” says Michael Hutchins, director of science for the American Zoo and Aquarium Association in Silver Spring, Md. The short report, based on Clubb’s dissertation project, doesn’t provide information on individual zoos. Hutchins suggests that the data may reflect animals raised under outmoded care.

Could zoos design enclosures to keep vulnerable animals properly? “It’s a possibility,” says Clubb. “From the data we’ve got, we don’t know.”

“I believe research like this is essential,” says Richard Lattis, general director of the Bronx Zoo in New York. For all captive animals, zoos follow a learning curve, he says. Fifty years ago, “we didn’t know how to breed gorillas,” he says, but now zoo populations are thriving.

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