Lateralization influences contest behaviour in domestic pigs

Irene Camerlink,Sophie Menneson,Gareth Arnott,Simon P Turner,Marianne Farish

doi:10.1038/s41598-018-30634-z

Abstract

Cerebral lateralization, i.e. hemispheric asymmetries in structure and function, relates in many species to a preference to attack from their left. Lateralization increases cognitive capacity, enabling the simultaneous processing of multiple sources of information. Therefore, lateralization may constitute a component of fighting ability (Resource Holding Potential), and/or influence the efficiency of information-gathering during a contest. We hypothesized that lateralization will affect contest outcome and duration, with an advantage for more strongly lateralized individuals. In 52 dyadic contests between weight-matched pigs (Sus scrofa; n = 104; 10 wk age), the direction of orientation towards the opponent was scan sampled every 10 s. Laterality indexes (LI) were calculated for the direction and strength of lateralization. Up to 12.5% of the individuals showed significant lateralization towards either the right or left but lateralization was absent at the population level. In line with our hypothesis, animals showing strong lateralization (irrespective of direction) had a shorter contest duration than animals showing weak lateralization. Winners did not differ from losers in their strength or direction of lateralization. Overall the results suggest that cerebral lateralization may aid in conflict resolution, but does not directly contribute to fighting ability, and will be of value in the study of animal contests.

Highlights

IntroductionI.e. hemispheric asymmetries in structure and function, relates in many species to a preference to attack from their left
Cerebral lateralization, i.e. hemispheric asymmetries in structure and function, relates in many species to a preference to attack from their left
Lateralization at the individual level refers to the lateralization that an individual shows whereas lateralization at the population level refers to an overall tendency of the population to move in a certain direction or to perform tasks with a preference for either their left or right side[12], such as handedness in humans[2,13]

Summary

Introduction

I.e. hemispheric asymmetries in structure and function, relates in many species to a preference to attack from their left. This contralateral organisation of the forebrain is not present in invertebrates, where the brain-body connections are predominantly ipsilateral (i.e. on the same side of the body) the central nervous system of invertebrates does have bilateral connections showing parallels with vertebrates[10,11] In both vertebrates and invertebrates, the use of the left/right limb or eye has been used in research as an indicator of cerebral lateralization. Lateralization can be studied for its direction, with either an individual-level or population-level preference to use left or right in a certain situation, and for the strength of lateralization, indicating the degree of integration between the hemispheres[12]. Contests in invertebrates is growing (fruit fly Bactrocera oleae[19]; fruit fly Ceratitis capitata[20]; blowfly Calliphora vomitoria[21])

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