Can urbanization accentuate hand use in the foraging activities of primates?

OBJECTIVES: How a species uses its anatomical manipulators is determined by its anatomy, physiology, and ecology. While ecology explains interspecific variation in gripping, grasping, and manipulating objects, its role in intraspecific variation in mouth- and hand-use by animals is less explored. Primates are distinguished by their prehensile capabilities and manual dexterity. In context to the adaptive pressures of urbanization on primates, we examined if mouth and hand use differed across the forest-urban gradient in food retrieval and processing under experimental and naturalistic conditions in cercopithecids, a family comprising several urbanizing primates. MATERIALS AND METHODS: We recorded the acquisition and processing of peanuts under experimental conditions in three groups of bonnet macaques (BM, Macaca radiata) differing in their dietary dependence on packaged food items along a rural-urban gradient. To affirm the pattern obtained in the experiment, we coded food acquisition of three cercopithecid species in similar habitats from video sources. RESULTS: Urban macaques had a disproportionately higher hand use to acquire and process peanuts while rural macaques had higher mouth use. Based on analyses of videos, urban populations of BM, Japanese macaque (M. fuscata) and vervet monkey (Chlorocebus pygerythrus) showed a bias toward hand use during food acquisition. DISCUSSION: The adaptive pressures of urbanization, like the manual constraints of extracting packaged foods and perhaps, the need for visual-haptic exploration of novel objects seem to accentuate hand use in synanthropic groups of primates. Additional research should ascertain similar patterns in other primates and determine specific aspects of urbanization that modulate the observed trend.

Losing its ground: A case study of fast declining populations of a 'least-concern' species, the bonnet macaque (Macaca radiata).

The populations of many species that are widespread and commensal with humans have been drastically declining during the past few decades, but little attention has been paid to their conservation. Here, we report the status of the bonnet macaque, a species that is considered 'least-concern' for conservation. We show that the widely ranging rhesus macaque is expanding its range into the distributional range of the bonnet macaque, a species endemic only to southern India. Bonnet macaques have very low abundance in forests of all types indicating that it is not a typically forest dwelling species. The traditionally preferred habitats of bonnet macaques have been Hindu temples/ tourist spots but our data reveal that nearly 50% population of bonnet macaques has disappeared from such previously occupied spots. Another preferred habitat of bonnet macaques has been roadsides with abundant Ficus trees adjoining croplands. We found that between 2003 and 2015, the roadsides have drastically changed where vegetation has been replaced with barren lands and urbanization. Consequently, the populations of bonnet macaques have declined by more than 65% over the past 25 years, and by more than 50% between 2003 and 2015 alone. We, therefore, conclude that this 'least-concern' species is actually facing serious conservation challenges. We also identify a few places such as small hillocks with natural vegetation and a few temples/tourist spots which are likely to remain stable and thus can serve as 'bonnet macaque conservation reserves'. Since the bonnet macaque shares many traits with several other commensal and 'low-risk' species, it can serve as a model for the development of long-term conservation strategies for most such species.