Flexibility in food extraction techniques in urban free-ranging bonnet macaques, Macaca radiata.

Elsa Addessi,Madhur Mangalam,Mewa Singh

doi:10.1371/journal.pone.0085497

Elsa Addessi, Madhur Mangalam + Show 1 more

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https://doi.org/10.1371/journal.pone.0085497

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Abstract

Non-human primate populations, other than responding appropriately to naturally occurring challenges, also need to cope with anthropogenic factors such as environmental pollution, resource depletion, and habitat destruction. Populations and individuals are likely to show considerable variations in food extraction abilities, with some populations and individuals more efficient than others at exploiting a set of resources. In this study, we examined among urban free-ranging bonnet macaques, Macaca radiata (a) local differences in food extraction abilities, (b) between-individual variation and within-individual consistency in problem-solving success and the underlying problem-solving characteristics, and (c) behavioral patterns associated with higher efficiency in food extraction. When presented with novel food extraction tasks, the urban macaques having more frequent exposure to novel physical objects in their surroundings, extracted food material from PET bottles and also solved another food extraction task (i.e., extracting an orange from a wire mesh box), more often than those living under more natural conditions. Adults solved the tasks more frequently than juveniles, and females more frequently than males. Both solution-technique and problem-solving characteristics varied across individuals but remained consistent within each individual across the successive presentations of PET bottles. The macaques that solved the tasks showed lesser within-individual variation in their food extraction behavior as compared to those that failed to solve the tasks. A few macaques appropriately modified their problem-solving behavior in accordance with the task requirements and solved the modified versions of the tasks without trial-and-error learning. These observations are ecologically relevant – they demonstrate considerable local differences in food extraction abilities, between-individual variation and within-individual consistency in food extraction techniques among free-ranging bonnet macaques, possibly affecting the species’ local adaptability and resilience to environmental changes.

Highlights

Animals respond to novel and unpredictable challenges in their physical and social environments by showing new or modified behavioral patterns, a phenomenon referred to as behavioral flexibility
Experimental Procedure In order to examine local differences in food extraction abilities, we presented the macaques of the roadside and the temple group with two distinct food extraction tasks: (a) task-1, a 400 ml unsealed PET bottle containing ca. 50 ml of sweet milk (Figure S1); and (b) task-2, a wire mesh box containing an orange (Figure S2)
In order to examine behavioral patterns associated with higher efficiency in food extraction, we presented the two temple group macaques AM1 and AF4 with manipulated versions of task-1: (a) task-1a, an unsealed PET bottle without cap-seal (Figure S3A); (b) Task-1b, an unsealed PET bottle with a relatively small capseal as compared to normal, such that there was a significant gap between cap and cap-seal (Figure S3B); (c) Task-1c, a PET bottle with an immovable cap and cap-seal (Figure S3C); (d) Task-1d, a PET bottle with a non-functional cap and capseal, such that even rotating the cap would not loosen the cap (Figure S3D)

Summary

Introduction

Animals respond to novel and unpredictable challenges in their physical and social environments by showing new or modified behavioral patterns, a phenomenon referred to as behavioral flexibility. Variation in behavioral flexibility among populations and individuals results in phenotypic diversity, i.e., populations and individuals respond differently to different environmental conditions. Existing populations of non-human primates, other than responding appropriately to naturally occurring challenges, need to cope with anthropogenic factors, such as environmental pollution, resource depletion, and habitat destruction [7,8,9]. Within such populations, adaptive variation in behavioral flexibility, or the expression of novel behavioral phenotypes, may have significant ecological and evolutionary consequences [10,11]. Ecological constraints on behavioral plasticity, through means of natural selection, may influence individuals’ responses to environmental heterogeneity, i.e., behavioral flexibility may increase or decrease, depending upon the adaptability of behavioral traits across a range of environmental conditions; overall, behavioral traits may vary between individuals but remain consistent within each individual [12,13,14]

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