Worldwide, primates are affected by habitat conversion into agriculture. Apart from the apparent impacts of habitat loss and fragmentation, primates face various threats when foraging in monocultures, including increased exposure to predators, hunters, but also to harmful chemicals. However, knowledge on the impacts of agricultural pesticides on wild primates is lacking. This project aims to explore the effects of pesticides commonly used in Malaysian oil palm plantations on the health of an endangered primate species, the southern pig-tailed macaque (Macaca nemestrina). As we have shown in previous studies, Macaca nemestrina regularly enters oil palm plantations to forage for food on the ground that can be potentially contaminated with harmful chemicals and their derivates from herbicides, insecticides, rodenticides, and chemical fertilizers.