Captive breeding of critically endangered species should be considered a last resort, not a long-term solution for survival, warn leading conservationists from Yale, the National Zoo and the San Diego Wild Animal Park.
Some revisions being considered by Congress for the Endangered Species Act would greatly emphasize expensive captive breeding programs, note the researchers, who urge instead a careful, case-by-case analysis of the costs and benefits of all conservation alternatives, including recovery programs in the wild.
In an article in the April issue of Conservation Biology, the researchers argue that the use of captive breeding has increased enormously in recent years without a parallel growth in understanding its limitations, such as high costs, risks of disease and lack of success in reintroducing the animals to the wild.
"Captive breeding is no panacea for saving endangered species," says Steven R. Beissinger, one of the authors and an associate professor of ecology and conservation biology at the School of Forestry and Environmental Studies. "In some cases, captive breeding has meant the difference between survival and extinction. By no means are we saying it shouldn't be used in those cases, but captive breeding is being proposed with increasing frequency when it's not appropriate."
Advances in captive breeding techniques, such as the successful in vitro fertilization process recently used with cheetahs, have focused public attention on the possibility of rescuing glamorous species. However, the long-term survival of endangered species hinges on their success in the wild, say the authors, all of whom have been involved in recovering endangered species -- from California condors to Hawaiian crows, whooping cranes, black-footed ferrets, snail kites and Puerto Rican parrots. In addition to Professor Beissinger, the researchers are Noel F.R. Snyder, Wildlife Preservation Trust International; Scott R. Derrickson, National Zoological Park; James W. Wiley, Grambling State University Cooperative Wildlife Project; Thomas B. Smith, biologist at San Francisco State University; William D. Toone, San Diego Wild Animal Park; and Brian Miller, Fundacion Ecologia de Curxmala, Jalisco, Mexico.
About 70 percent of recovery plans for endangered species advocate breeding in captivity, but such programs should not overlook efforts to increase populations in the wild, the researchers argue. "Roughly half of the 330 parrot species in the world have been recommended for captive breeding, along with about one-third of the roughly 3,500 endangered vertebrate species," says Professor Beissinger, who is a specialist in the conservation of endangered birds, especially parrots, and curator of ornithology at the Peabody Museum of Natural History. "That's just not feasible. There is not enough room in zoos, and few species can survive in the wild after being raised for generations in captivity."
People need to understand that animals can become domesticated in as little as two generations in captivity -- making it impossible for them to survive in the wild, Professor Beissinger says. In fact, only 11 percent of 145 programs to reintroduce captive-bred species to the wild have been successful thus far, according to a recent study.
Other limitations of captive breeding include low fertility rates that make it difficult to sustain population levels, lack of administrative continuity and stable funding to maintain long-term programs, and diseases spread by close contact with species not encountered in the wild. Inbreeding can also make captive-bred species more susceptible to disease, the researchers note.
In addition, the existence of captive populations can give a false impression that the species is safe, so destruction of habitats and wild populations can proceed unchecked, the researchers warn. Moreover, long- term solutions are often politically more difficult to fund than captive breeding programs, so it is tempting for the U.S. Fish and Wildlife Service and other groups to deemphasize efforts to save wild populations once captive populations are in place, they add.
"More attention should be focused on correcting conditions in the wild that are threatening species survival," says Professor Beissinger. "Instead of taking a species-by-species crisis approach to conservation, we should focus on preserving the ecosystems that support a wide variety of plants and animals. It's much more cost-effective to intervene before a crisis occurs."
Zoos probably help preserve biodiversity more through their capacities for public education, professional training, research and support of conservation efforts in the wild than by captive breeding of endangered species, he adds.