Resource partitioning in sympatric langurs and macaques in tropical rainforests of the central Western Ghats, south India.

In a competitive sympatric association, coexisting species may try to reduce interspecific interactions as well as competition for similar resources by several ecological and behavioral practices. We studied resource utilization of three sympatric primate species namely, lion-tailed macaques (Macaca silenus), bonnet macaques (M. radiata) and Hanuman langurs (Semnopithecus entellus) in a tropical rainforest of the central Western Ghats, south India. We studied resource use, tree-height use, foraging height, substrate use when consuming animal prey and interspecific interactions. The results revealed that across the year, there was very limited niche overlap in diet between each species-pair. Each primate species largely depended on different plant species or different plant parts and phenophases from shared plant species. Primate species used different heights for foraging, and the two macaque species searched different substrates when foraging on animal prey. We also recorded season-wise resource abundance for the resources shared by these three primate species. While there was low dietary overlap during the dry season (a period of relatively low resource abundance), there was high dietary overlap between the two macaque species during the wet season (a period of high resource abundance for the shared resources). We observed only a few interspecific interactions. None of these were agonistic, even during the period of high niche overlap. This suggests that the sympatric primate species in this region are characterized by little or no contest competition. Unlike in some other regions of the Western Ghats, the lack of interspecific feeding competition appears to allow these primates, especially the macaques, to remain sympatric year-round.

Diet and dietary-niche breadth of diurnal rain forest primates in the Central Western Ghats, India.

We studied the feeding ecology of 3 sympatric primate species, the lion-tailed macaque (Macaca silenus), bonnet macaque (Macaca radiata) and Hanuman langur (Semnopithecus entellus), in a tropical rain forest of the Central Western Ghats, India. Since the availability of leaves is much higher than that of fruits, we expected that the primarily folivorous langurs would use a larger number of resources than the primarily frugivorous macaques. Since fruits are a relatively total resource, unlike leaves, of which only selected parts are consumed, we expected that the primarily frugivorous macaques would use resources more proportionately than the folivorous langurs, resulting in a wider food niche breadth in macaques. We collected data on these primate species over a period of 2 years using scan sampling in a contiguous rain forest. We calculated Levin's standardised food niche breadth for each species. Langurs used a larger number of tree species than macaques, but their niche breadth was narrower than that of macaques. The majority of their diet (over 50%) came from only a few trees in the case of all three primate species. Long-term data are provided herein for the first time on the feeding ecology of bonnet macaques and Hanuman langurs in a tropical rain forest.

Drastic population decline and conservation prospects of roadside dark-bellied bonnet macaques (Macaca radiata radiata) of southern India.

We carried out a survey on roadside dark-bellied bonnet macaques (Macaca radiata radiata) on the highways around the south Indian city of Mysore. The present survey was the fourth since 1989 on the same populations. We divided the habitats into intensive cultivation (IC), wet cultivation (WC), and scrub forests (SC). The number of groups has significantly reduced from 54 to 31 and the number of animals has declined from 1,207 to 697 from 1989 to 2009. This decline has been recorded only in the IC and WC areas, whereas the population in SC with places of Hindu worship has remained stable. Due to the loss of roadside Ficus trees over the years, the habitat of the monkeys has almost disappeared. Since bonnet macaque is not primarily a forest-dwelling species, the seemingly widespread primate may soon become 'threatened' if the non-forest populations continue to decline. Scrub forests in small hillocks housing Hindu temples remain the only prospective places for conservation of bonnet macaques.