Jakarta - Zoos in Indonesia are mistreating endangered orangutans, forcing the great apes to live in cages and depriving them of adequate water and food, a conservation group said Wednesday.

The Centre for Orangutan Protection (COP) said its study showed that most zoos in five major Indonesian cities locked up orangutans in cages instead of keeping them in more spacious enclosures.

Many of the orangutans observed showed symptoms of mental stress such as banging themselves against objects, throwing up and eating their vomits, and spending time lying down or sitting, said Luki Wardhani, a researcher for the group.

"They don't get adequate access to water, don't interact with each other and live in cages without playing facilities," she said.

The COP said the orangutans were mostly used as objects of amusement for visitors.

The World Wildlife Fund for Nature estimates there are about 50,000 orangutans in Indonesian and Malaysian forests. (dpa)