Thousands of monkeys were sterilised this month to control their surging population in Thailand. Wildlife conservation officers used bananas to lure the adult primates into cages laid around Hup Pa Tat Valley in Uthai Thani province on April 1. The Assam macaques were then sedated using tranquilizer darts while being held inside the steel cages so that officers could easily take them to a makeshift clinic nearby for the operation. The clever monkeys tried to evade the officers at first giving them a hard time in trapping the animals but they were lured in upon using food bait. Tham Prathun Non-hunting Area chief Jarat Khamphaeng chief said the mass sterilisation was expected to reduce the population of monkeys as they had recently been causing problems by raiding several farms to steal crops. He said: ‘The overpopulation has forced the macaques to find food sources outside the forest and they have now started to disturbe humans. We sterilised as many as we could for now and we hope to notice the changes in the coming months.’ The unconscious monkeys were carried one-by-one to a mini-hospital set up where veterinarians spayed and neutered the wild animals. Veterinarians did small cuts in the ducts that transport sperm in the male monkeys while the females faced an abdominal operation to remove their ovaries or uterus. After the operation, their sizes were taken before being tattooed with a serial number on their arms for documentation. The animals were also given antibiotics to prevent the stitches from being infected as well as parasite cleansing. The operation lasted up to two hours per monkey done by a team of volunteer vets. They were released back to the forest the next day (April 2) after having enough rest and being fed. Chief Jarat added that they have warned tourists and locals to stop feeding the wild animals to prevent interaction with them. He said: ‘The most important thing is that humans have to stop feeding wild animals and let them stay where they belong.’ The Minister of Natural Resources and Environment had set a budget specifically for sterilising the monkeys this year after attacks have been reported all over the country. Data from the Wildlife Conservation Office reported that more than a hundred thousand monkeys had entered the residential areas in around 50 provinces making noise, eating crops, destroying garbage bins, and biting people. A government agency study showed that tourists feeding monkeys were one of the key factors resulting to overpopulation as most food that they consumed had a high quantity of carbohydrates causing a change in their eating habits and a higher sexual drive. Officials are now considering creating a ‘monkey colony’ project or moving the animals to an island over the past two years as an alternative to mass sterilisation.