A tough nut to crack? Proficiency in coconut processing of the Nicobar long-tailed macaque Macaca fascicularis umbrosus

The ability to manipulate objects enables macaques to utilize resources well. Coconut ( Cocos nucifera ) is one such food that has high energy and nutrient value but requires complex motor skills for extraction. In this study, we examined the proficiency of a single group of Macaca fascicularis umbrosus from Campbell Bay, India, in feeding on different types of coconuts. The group comprised 16 individuals with 3 adult males, 6 adult females, 3 sub-adult males, and 4 infants. We observed individuals feeding on tender, mature, dry, and dry-dehusked coconuts in 90 feeding bouts between August 2013 and December 2015. Their feeding behaviour was divided into four types of behavioural acts: pluck, process, drink, and feed. We prepared an ethogram consisting of 32 behavioural acts associated with feeding on coconuts, and recorded the occurrence of these acts during focal animal sampling. We used NMDS to examine differences among age/sex classes in the occurrence of behavioural acts associated with feeding on coconuts. Although females and males showed no significant separation in these behaviours, adults and young individuals formed distinct groups. However, only 3 out of 32 acts were exclusive to age classes. Using Discrete Time Markov Chain analysis, we found that adults tended to transition back to processing behaviours after drinking and feeding behaviours more often than young individuals. An almost similar repertoire of behaviours among age and sex classes indicates that there is no single model behaviour. Further, this study indicates that among different age/sex classes, adults tend to maximise the nutritional gains during single feeding bouts than younger individuals.