Posture does not matter! Paw usage and grasping paw preference in a small-bodied rooting quadrupedal mammal.

Marine Joly,Elke Zimmermann,Marina Scheumann

doi:10.1371/journal.pone.0038228

Marine Joly, Elke Zimmermann + Show 1 more

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https://doi.org/10.1371/journal.pone.0038228

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Abstract

BackgroundRecent results in birds, marsupials, rodents and nonhuman primates suggest that phylogeny and ecological factors such as body size, diet and postural habit of a species influence limb usage and the direction and strength of limb laterality. To examine to which extent these findings can be generalised to small-bodied rooting quadrupedal mammals, we studied trees shrews (Tupaia belangeri).Methodology/Principal FindingsWe established a behavioural test battery for examining paw usage comparable to small-bodied primates and tested 36 Tupaia belangeri. We studied paw usage in a natural foraging situation (simple food grasping task) and measured the influence of varying postural demands (triped, biped, cling, sit) on paw preferences by applying a forced-food grasping task similar to other small-bodied primates. Our findings suggest that rooting tree shrews prefer mouth over paw usage to catch food in a natural foraging situation. Moreover, we demonstrated that despite differences in postural demand, tree shrews show a strong and consistent individual paw preference for grasping across different tasks, but no paw preference at a population level.Conclusions/SignificanceTree shrews showed less paw usage than small-bodied quadrupedal and arboreal primates, but the same paw preference. Our results confirm that individual paw preferences remain constant irrespective of postural demand in some small-bodied quadrupedal non primate and primate mammals which do not require fine motoric control for manipulating food items. Our findings suggest that the lack of paw/hand preference for grasping food at a population level is a universal pattern among those species and that the influence of postural demand on manual lateralisation in quadrupeds may have evolved in large-bodied species specialised in fine manipulations of food items.

Highlights

First thought to be a unique trait in humans, a side bias in limb preference has been reported in a variety of tetrapod species (e.g. [1,2,3,4,5,6])
Our findings suggest that the lack of paw/hand preference for grasping food at a population level is a universal pattern among those species and that the influence of postural demand on manual lateralisation in quadrupeds may have evolved in large-bodied species specialised in fine manipulations of food items
It has been shown that a side bias in limb usage at a population level seems to be constrained by phylogeny and varies according to ecological variables such as body size, foraging mode and postural habit [12,13,14]

Summary

Introduction

First thought to be a unique trait in humans, a side bias in limb preference has been reported in a variety of tetrapod species (e.g. [1,2,3,4,5,6]). It has been shown that a side bias in limb usage at a population level seems to be constrained by phylogeny and varies according to ecological variables such as body size, foraging mode and postural habit [12,13,14]. A recent analysis in 23 different Australian parrot species showed that while direction and strength of lateralisation are constrained by phylogeny, the strength of laterality varies between the species, probably due to a shift in foraging mode [12]. Marsupials, rodents and nonhuman primates suggest that phylogeny and ecological factors such as body size, diet and postural habit of a species influence limb usage and the direction and strength of limb laterality. To examine to which extent these findings can be generalised to small-bodied rooting quadrupedal mammals, we studied trees shrews (Tupaia belangeri)

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