Elephants have lived in captivity for more than 4,000 years, many of them held in zoos and circuses worldwide. Captive elephants are also used in some Asian countries for timber-logging and in religious ceremonies.
Ros Clubb of Oxford University, a zoologist and co-author of the report, said the study was done after "work by other biologists had already set alarm bells ringing."
Findings have shown, for example, that 35 percent of zoo females fail to breed and that 15 to 25 percent of Asian elephant calves are stillborn.
Clubb and her co-author, Georgia Mason, also a zoologist at Oxford University, said females in the wild normally don't conceive until around 18 years of age, but female elephants in zoos often begin breeding as early as age 12, putting them and their offspring at higher risk of death and illness.
The researchers also found that zoo elephants are often overweightup to 50 percent heavier than their counterparts in the wildand commonly exhibit unusual behavior such as weaving to and fro.
Mason said such conditions likely stem from a combination of ill health, unusually small social groupings, inadequate dwelling space, and European weather that is often colder than in the elephants' native habitats.
Female elephants in the wild live in interactive family groups of up to ten individuals, said Mason. The female calves usually remain in their family group for life and develop strong bonds with members of that group. In contrast, zoo elephants are typically found in groups of two, and two-thirds of female calves are taken from their mothers at an early age.
This low level of family structure and the relatively small enclosures of zoos contribute to boredom and distress, said Mason. Wild elephants roam over distances as much as 60 to 100 times larger than typical zoo housing for elephants.
Although the RSPCA-sponsored study was limited to European zoos, Mason believes the findings may be widely applicable. "Studies of U.S. zoos certainly show that they too have had problems with high [elephant] infant mortality," she said, adding that researchers should "look to see if similar things are happening there."
Lori Eggert, who studies elephant genetics and behavior at the Smithsonian Institution in Washington, D.C., agreed that it's important to ensure zoo elephants' comfort and welfare but said meeting the demands called for in the study would be challenging. "Elephants [in the wild] require lots of room, and trying to closely mimic their natural habitat or large social groups would be very difficult," she said.
The Federation of Zoological Gardens of Great Britain and Ireland said in a statement that its members remained committed to improving the welfare of their elephants. "Given the bleak outlook for elephants in the wild, zoo elephants have an increasingly valuable role to play," the statement said.
Apart from their drawing power as major wildlife attractions, zoo elephants are important for conservation, research, and public education.
"Elephants are generally used as a flagship species," said Eggert. "As such, they inspire awe and love for nature in people and further inspire them to open their pocketbooks to give money for conservation of habitats."
Eggert said working with zoo elephants was indispensable to her own research achievements. Much understanding about animal biology and behavior, such as forms of communication and patterns of reproduction, have been based on research involving elephants and other zoo animals, providing research opportunities that would be difficult or impossible in the world, Eggert explained.
"There are a lot of strong beliefs out there, but now we need real, objective data on what captive elephants need," said Mason. "Only then," she added, "can we judge whether zoos can ever reliably keep these animals well."
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