Sharing from the Same Bowl: Resource Partitioning between Sympatric Macaque Species in the Western Himalaya, India

Abstract

Comparative studies of closely related species with similar ecological requirements are essential to understand the behavioral adaptations that allow them to live in sympatry. We investigated the mechanisms that enable the coexistence of two congeneric macaques—the Assamese macaque (Macaca assamensis) and rhesus macaque (M. mulatta)—in the Western Himalaya along the India–Nepal border in the State of Uttarakhand, India. For five months from December 2016, we collected scan samples of the behavior of one Assamese macaque group (N = 9975 samples) and two rhesus macaque groups (N = 14,402). Activity budget comparisons revealed that the former spent more time on feeding and the latter on resting and moving. Although the two species had 29 (37%) of 78 food items in common, only Mallotus philippensis and agricultural crops formed a major part of their shared diet (contributing to >1% of feeding scans). The Assamese macaque fed predominantly on leaves and had a broader niche than did the rhesus macaque, which fed mostly on fruits. We also observed differences in feeding schedules and feeding heights of the two species. The two species showed variation in home range, daily movement patterns, habitat use, and sleeping sites that need further investigation. The two species exhibited a lower dietary and spatial niche overlap in winter, a period of relatively low resource abundance than in spring. The observed differences in diet and space use suggest that the niches of the two macaques are separated in several dimensions, which may have promoted their coexistence in this region. Similar long-term studies across different habitats and seasons can improve our understanding of resource use by primates in sympatry.