Distribution and Human-Mediated Establishment of Crested Macaque (Macaca nigra) Populations in the North Moluccas, Indonesia

Abstract Over the course of human history, people have translocated plant and animal species, often with profound consequences. Understanding how endangered species adapt to human-mediated migration and novel environments is crucial to inform conservation strategies. The crested macaque ( Macaca nigra ), an endemic primate species of North Sulawesi (Indonesia), faces imminent extinction in its native range due to anthropogenic threats. While extensive research on this species has been conducted in the Duasudara Nature Reserve in North Sulawesi, critical knowledge gaps persist with regard to their distribution outside this protected area on Sulawesi and beyond. Previous studies report that crested macaques were introduced by humans to North Maluku ~200 hundred years ago. In 2023, we visited Bacan, Kasiruta, and southern Halmahera Island, conducting interviews, surveys, and direct observations of macaques to determine their presence or absence on these islands. We encountered wild crested macaques or their feces at 23 locations across these islands and pet macaques in 6 locations on Bacan. We confirm crested macaques on Bacan and also report them at Kasiruta and in the south of Halmahera, with results of our interviews suggesting that macaques might be present in North Maluku for ~500 years. We found no evidence of their presence on Mandioli. Additionally, we documented behavioral similarities, e.g., loud calls specific to male crested macaques. Our results extend the known distribution range of crested macaques by the islands of Kasiruta and Halmahera, shedding light on the potential for these populations to contribute to the survival of the species.