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