Hong Kong on Monday hailed the success of a birth control programme for the city\'s wild monkeys, saying the primates\' numbers have dropped 15 percent over four years. Officials said the latest monkey census showed the population stood at 1,965 last year, down from 2,320 in 2008 -- a year after the city started fertility controls for the primates using methods including vasectomies. The conservation department said about 70 percent of the monkeys had been treated under the \"monkey desexing programme\". All treated monkeys were implanted with a microchip for identification. The government decided to take action after receiving numerous complaints from the public including reports of aggressive monkeys chasing hikers for food. It is illegal to feed monkeys in the southern Chinese city, punishable with a fine of up to HK$10,000 ($1,300).