Play fighting social networks do not predict injuries from later aggression

Simon P Turner,Andrea Doeschl-Wilson,Simone Foister,Gareth Arnott,Irene Camerlink,Jennifer E Weller,Taegyu Choi,Marianne Farish

doi:10.1038/s41598-020-72477-7

Abstract

Early play fighting mimics later aggression in many species, and may, therefore, be expected to reduce costs from later aggressive interactions. Using social network analysis (SNA) the effect of a central play fighting network position on later skin lesions from aggression was assessed in domestic pigs. Piglets (n = 263) were kept in litter groups or socialised pre-weaning with another litter to enhance play fighting experience. Play fighting was recorded for 1.5 h per day over 6 days pre-weaning. Play fighting network centrality was quantified using measures of individual network position and entire network structure (degree, eigenvector, betweenness, clustering coefficient). Skin lesions from aggression were counted after a dyadic contest and at 24 h and 3 weeks following group mixing. Pigs with play fighting interactions with many partners experienced fewer lesions from the dyadic contest (in-degree, p = 0.01) and tended to received fewer lesions 3 weeks after group mixing (degree, p = 0.088) but no other play fighting centrality measures affected the number of lesions at any point. The benefits of play fighting were therefore limited to specific aggressive social contexts. The tendency of socialised piglets to play fight with non-littermates did not affect subsequent lesions. We advocate the use of SNA over approaches that only consider dyadic interactions to further our understanding of the influence of early social group interactions on later life experience.

Highlights

Faithfully mimics adult fighting except in the scarcity of injuries, the honouring of submissive signals following defeat and the willingness of defeated animals to stimulate new bouts of interaction
In the context of social play, social network analysis can quantify novel characteristics such as how central or peripheral an individual is in the play fighting network, whether its position is key in the group and the extent to which its play partners are experienced in play
We test whether centrality of piglets in their play fighting network predicts the number of skin lesions resulting from a dyadic contest between two unfamiliar pigs several weeks later and thereafter in the highly dynamic scenario of formation of a new social group

Summary

Introduction

Faithfully mimics adult fighting except in the scarcity of injuries, the honouring of submissive signals following defeat and the willingness of defeated animals to stimulate new bouts of interaction. In the context of social play, social network analysis can quantify novel characteristics such as how central or peripheral an individual is in the play fighting network, whether its position is key in the group (e.g. operating as the gatekeeper between play subgroups) and the extent to which its play partners are experienced in play Despite these benefits, to our knowledge no study has examined how position in a play fighting network affects later outcomes of aggressive behaviour. We test whether centrality of piglets in their play fighting network predicts the number of skin lesions resulting from a dyadic contest between two unfamiliar pigs several weeks later and thereafter in the highly dynamic scenario of formation of a new social group. We predict that piglets that play fight with non-littermates when given the opportunity of early-life socialisation will receive fewer injuries from later life aggression than those which play preferentially with littermates (Prediction 2)

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Conclusion