In 2013, the long-tailed macaque Macaca fascicularis was categorized as one of the 100 worst invasive alien species (Luque et al., 2013, Nature, 498, 37). However, its population has declined as a result of conflicts with people, trade for pets and for the medical industry (Hansen et al., 2019, Conservation Science and Practice, 1, e88). In addition, the Covid-19 pandemic increased the demand for this species because of its use in vaccine development (Hansen et al., 2021, Primate Conservation, 35, 1–11).

In March 2022, M. fascicularis was recategorized from Vulnerable to Endangered on the IUCN Red List (Hansen et al., 2022). However, the fact that M. fascicularis is recognized as a pest in some regions of Indonesia has raised concerns regarding the conservation of this species, especially in North Sumatra Province.

The subspecies in North Sumatra Province is M. fascicularis fascicularis (Liedigk et al., 2015, BMC Genomics, 16, 1–11); it is considered a destructive feeder on crops in this area (Marchal & Hill, 2009, Primate Conservation, 24, 107–116). One of the areas where M. f. fascicularis is considered a pest is Parapat, Lake Toba, Simalungun Regency. On the journey from Medan (the capital city of North Sumatra Province) to Parapat one can observe large numbers of M. f. fascicularis gathering along the road, waiting for travellers to hand them food. From a conservation point of view this is inappropriate because of potential negative effects on the species. Foraging along the road also increases the likelihood of individuals colliding with vehicles.

In early 2022, we received reports of M. f. fascicularis feeding on crops in villages near Parapat, and the local communities consider the species a pest. Although there are as yet no records of the hunting or killing of M. f. fascicularis in this area, any increase in conflict with the species could potentially encourage local communities to persecute it.

Studies are required to assess the population of the long-tailed macaque in several regions of Indonesia, notably on Sumatra. In particular, given the species’ Endangered status, studies are required to determine the causes of the species’ exploration for food near roads and crop use in community gardens.