Wild monkeys on the mainland have been under pressure from human activity for hundreds of years. Emperors during the Qing dynasty were partial to scooping out the brain of a living monkey for a tasty treat, and the practice continues to this day, particularly in some southern provinces. For the past 50 years, people have hunted wild primates for use in medicine, for export and for scientific experiments, driving most species to extinction or close to it. The massive hunting of monkeys started as soon as the People's Republic was founded. More than 50,000 rhesus monkeys were captured in government-organised hunts in Guangxi and sent to the Soviet Union in the 1950s, according to regional government figures. A 1998 national survey suggested there were only 25,000 rhesus monkeys left on the mainland. Eight years later, a group of zoologists from the Chinese Academy of Sciences (CAS) found that 70 per cent of that population had disappeared. And the situation is far worse for other species, as rhesus monkeys are the most prevalent primate on the mainland. For example, there are just 15 of the once-populous Hainan gibbon left, making it the world's most threatened primate species. Monkeys also have played a role in traditional Chinese medicine, which maintains that the meat, bones and livers of monkeys have various curative effects, ranging from detoxification to improving sex drive. State-owned medicine companies buy about 2 tonnes of monkey bones a year, taken from at least 1,500 primates. Some reports estimate the volume of trade on the black market is at least three times that. In addition, some people smuggle wild primates into the mainland and export them as domestic stock. In 2003, police broke up a Beijing-based monkey-trafficking network that had bought, transported and sold more than 7,000 primates overseas in just a couple of years. According to a CAS zoologist, the biggest consumers of wild primates are government-run scientific research institutes. He estimates that more than 8,000 monkeys are used in experiments on the mainland every year, and a large proportion of them are captured in the wild. 'You can buy a captured one from peasants for a few hundred yuan. But a captive-bred monkey from a regular farm will cost many thousands,' he said. 'The growing appetite [of these institutes] is accelerating the depletion of primate resources in China.'