A comparative assessment of hand preference in captive red howler monkeys, Alouatta seniculus and yellow-breasted capuchin monkeys, Sapajus xanthosternos.

Werner Kaumanns,Mewa Singh,Madhur Mangalam,Nasibah Sfar

doi:10.1371/journal.pone.0107838

Werner Kaumanns, Mewa Singh + Show 2 more

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https://doi.org/10.1371/journal.pone.0107838

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Abstract

There are two major theories that attempt to explain hand preference in non-human primates–the ‘task complexity’ theory and the ‘postural origins’ theory. In the present study, we proposed a third hypothesis to explain the evolutionary origin of hand preference in non-human primates, stating that it could have evolved owing to structural and functional adaptations to feeding, which we refer to as the ‘niche structure’ hypothesis. We attempted to explore this hypothesis by comparing hand preference across species that differ in the feeding ecology and niche structure: red howler monkeys, Alouatta seniculus and yellow-breasted capuchin monkeys, Sapajus xanthosternos. The red howler monkeys used the mouth to obtain food more frequently than the yellow-breasted capuchin monkeys. The red howler monkeys almost never reached for food presented on the opposite side of a wire mesh or inside a portable container, whereas the yellow-breasted capuchin monkeys reached for food presented in all four spatial arrangements (scattered, on the opposite side of a wire mesh, inside a suspended container, and inside a portable container). In contrast to the red howler monkeys that almost never acquired bipedal and clinging posture, the yellow-breasted capuchin monkeys acquired all five body postures (sitting, bipedal, tripedal, clinging, and hanging). Although there was no difference between the proportion of the red howler monkeys and the yellow-breasted capuchin monkeys that preferentially used one hand, the yellow-breasted capuchin monkeys exhibited an overall weaker hand preference than the red howler monkeys. Differences in hand preference diminished with the increasing complexity of the reaching-for-food tasks, i.e., the relatively more complex tasks were perceived as equally complex by both the red howler monkeys and the yellow-breasted capuchin monkeys. These findings suggest that species-specific differences in feeding ecology and niche structure can influence the perception of the complexity of the task and, consequently, hand preference.

Highlights

Non-human primates preferentially use one hand to perform a unimanual task, or to execute the most complex action while performing a bimanual task [1]
Consistent with the task complexity theory, studies on several non-human primate species reported that the same individuals that used both hands to a similar extent in simple unimanual reaching-for-food tasks (here, ‘reaching-forfood’ refers to the manual action involved in obtaining food using hand(s)/mouth), preferentially used one hand in the relatively complex bimanual tasks (red-capped mangabeys, Cercocebus torquatus [8], vervet monkeys, Chlorocebus aethiops [9], brown capuchin monkeys [11], white-faced capuchin monkeys, Cebus capucinus [12], olive baboons, Papio anubis [13], Campbell’s monkeys, Cercopithecus campbelli [14], De Brazza’s monkeys, Cercopithecus neglectus [15], Sichuan snub-nosed monkeys, Rhinopithecus roxellana [16], rhesus macaques, Macaca mulatta [17], gorillas, Gorilla gorilla berengei [18], and chimpanzees, Pan troglodytes [19])
We attempted to explore this hypothesis by comparing hand preference between species that differ in the feeding ecology and niche structure, namely red howler monkeys, Alouatta seniculus and yellow-breasted capuchin monkeys

Summary

Introduction

Non-human primates preferentially use one hand to perform a unimanual task, or to execute the most complex action while performing a bimanual task [1]. Thereon, with the evolution of a lesser arboreal lifestyle, the right hand was no longer required to obtain postural support and became specialized for manipulating objects while coordinating complex bimanual actions In this respect, studies on several non-human primate species reported that the same individuals that used both hands to a similar extent in unimanual reaching-for-food tasks that require tripedal/ quadrupedal posture, preferentially used the right hand in those tasks that require bipedal posture (red-capped mangabeys [8], tufted capuchin monkeys [23], bonobos, Pan paniscus [24], chimpanzees, and orangutans, Pongo pygmaeus [25]). Many other factors that these two theories do not consider could possibly have played a role in the evolution of hand preference in non-human primates, as well as in humans [5,26]

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