1Biopsychology laboratory, Department of Psychology, Institute of Excellence, University of Mysore, Manasagagothri, Mysuru-570006, India
2Wildlife Information Liaison Development, Coimbatore-641035, Tamil Nadu, India
3Primate Research Institute, Kyoto University, Inuyama, Aichi-484, Japan
Correspondence*Sayantan Das, Biopsychology laboratory, Department of Psychology, Institute of Excellence, University of Mysore, Manasagagothri, Mysuru-570006, India Email: sayantaniiser@gmail.com
ABSTRACT How a species differentially uses its appendages is determined by anatomy and physiology at a proximate level and by phylogeny and ecology at an ultimate level. Primates are often distinguished by their prehensile capabilities and manual dexterity characterized by complex skeletomuscular architecture, interconnected sensory systems and congruous cognitive mechanisms. However, species-specific predispositions and task-specific requirements can lead to differential use of anatomical manipulators. Theoretical explanations for intraspecific variation in the use of mouth and hands by nonhuman animals is non-existent. In context to the intense pressures of urbanization on natural habitats, we examined if hand and mouth use differed across the rural-urban gradient in tasks at the extreme ends of the complexity spectrum, food retrieval (simple) and food processing (complex and hierarchical) under experimental conditions in bonnet macaques (Macaca radiata ) and more generally, under naturalistic conditions in an additional two primate species (Japanese monkey,Macaca fuscata ; vervet monkey, Chlorocebus pygerythrus ). The use of hands in both tasks increased with urbanization and the converse was true for the use of mouth under experimental conditions. Even under naturalistic settings, all examined species of urban primates showed a bias in hand use during food acquisition. Thus, it appears that the adaptive pressures of urbanization, like the manual constraints of extracting packaged food and perhaps the need for visual-haptic exploration of novel objects accentuates hand use in even simple tasks among synanthropic groups of nonhuman primates. Additional research is needed to determine specific factors of urbanization influencing the trend observed and to ascertain similar patterns in other primates occupying forest-urban niches.
KEYWORDS hand use, packaged food, urbanization, synanthropic species