Pig-tailed macaques have a bad reputation as crop raiders, widely regarded as a pest in agricultural crops, including oil palm. But a new study shows they only cause only relatively minor losses in palm oil yield, and more importantly, they actively search for rats, a major oil palm pest. So are macaques acting as a biological pest control in oil palm plantations fringing their forest habitat? We speak to Dr Nadine Ruppert, a senior lecturer and zoologist at the School of Biological Sciences in Universiti Sains Malaysia, and the corresponding author for this study.