Xiku, the only grown chimp in the zoo of Urumqi, capital of Xinjiang Uygur Autonomous Region, succumbed to addiction by observing and mimicking humans when he performed in a circus several years ago.

"After Xiku came to stay in our zoo in September 2002, his nicotine addiction became ever stronger. He was smoking nearly twenty cigarettes a day compared with less than ten prior to coming here," said the keeper.

We were worried that smoking harmed Xiku's health, and began to control his smoking soon after he entered the zoo, said the keeper.

But to encourage the chimp to quit smoking was not easy. At the beginning, he became irascible when he wanted to smoke, jolting windows and doors, said the keeper.

Visitors to the zoo did not help the situation, tossing Xiku cigarettes for their own amusement.

We sometimes gave him some sunflower seeds or a bottle of beer to help him shake off the addiction and visitors are no longer allowed to throw him cigarettes, the keeper said.

Now, Xiku has gone through the pain barrier and has become less addicted to cigarettes, said the keeper. Xiku is now down to four a day.

"We are confident that Xiku will soon quit smoking completely with our help," the keeper said.