Anna Holzner

Worldwide, wildlife is critically affected by the conversion of natural habitats into agricultural land. The southern pig-tailed macaque (Macaca nemestrina, IUCN: endangered), a threatened yet largely understudied primate species inhabiting the rainforests of Southeast Asia, has lost large parts of its natural forest habitat to oil palm plantations. When entering these monocultures in search of food, the macaques face threats through an increased predation risk and conflicts with humans. My work focuses on providing detailed insights into the ability of this species to permanently adapt to these human-altered environments. The project is conducted in collaboration with Dr. Nadine Ruppert from Universiti Sains Malaysia.

During my PhD, I investigated the ability of M. nemestrina to flexibly adjust its diet and social behaviour to the forest-oil palm matrix. Partially diverting their foraging activities from forest into oil palm plantations, the macaques may benefit farmers as they actively hunt for plantation rats that cause substantial yield loss. Significantly reducing rat numbers, this primate can act as a biological pest control. However, M. nemestrina’s ability to adapt comes at cost of its social behaviour, the reduction of which is critical given that sociality significantly affects fitness, indicating the macaques’ strong dependency on the presence of nearby forest.

My current work focuses on further assessing the risks and benefits of macaques foraging in oil palm plantations from two different perspectives – the wildlife and the farmers. Based on chemical samples of macaques and the plantation environment, we aim at unravelling potential links between the intake of pesticide-contaminated plantation foods and the pesticide load of macaques, as we expect direct implications of the extensive use of pesticides on plantations for the health and fitness of M. nemestrina. Further, we aim at assessing how economic returns of primate friendly managed plantations compare to conventional managed plantations, taking into account the economic value of a sustainable plantation management, including biocontrol by macaques.

Present Position