KUALA LUMPUR, Malaysia - Veterinarians have been tracking three orangutans they implanted with tiny transmitters as part of efforts to protect the endangered primates once they reintroduce them to the wild, a Malaysian official said Monday.

French and Austrian veterinarians worked with the Wildlife Department in eastern Sabah state on Borneo island to implant specially designed coin-sized transmitters in the necks of the orangutans for the first time ever in September, said Senthilvel Nathan, the department's chief field veterinarian.

The orangutans' jungle habitat in Sabah has shrunk over the decades and their numbers have plummeted as loggers cut down the forests and plantation farming encroached.

Fewer than 11,000 orangutans remain in Sabah. Up to eight times that number existed 15 years ago, a French-based conservation group, Hutan, has estimated.

The three orangutans are among about 250 primates that were cared for by humans after being found sick, injured or orphaned when they were young. They now live in a 40 sq.-kilometre reserve that can only handle a limited number of them, Senthilvel said.

The transmitters will not be able to show any imminent threat to the orangutans, but they will allow officials to monitor their whereabouts in the wild and find them quickly if necessary.

Previous attempts to use radio-tracking collars on orangutans failed because they could easily take them off. The surgery on the three orangutans has shown no harmful side effects.

Officials have not decided when to release the animals into the wild or how many more orangutans would have the transmitters implanted.

Sabah authorities recently announced plans to bar companies from planting palm oil and other crops near rivers to preserve the natural habitat of orangutans, pygmy elephants, rhinoceroses, sun bears and other threatened animals.