Cognitive and non-cognitive factors predict pigs' positions in an aggression social network.

Social network analysis (SNA) provides a means of understanding animals' agonistic behaviour in a group. The aim of this study was to use SNA to characterise how individual cognitive performance affects agonistic behaviour. Using 175 pigs, we hypothesised that their choice of opponents would be affected by their ability to discriminate spatial information and to adapt their behaviour when cues were reversed. A spatial discrimination test was conducted; left and right locations were assigned as positive (food reward) and negative (fan) and each pig's learning speed was recorded. The cues were then reversed, and we tested whether pigs adjusted their behaviour. At age 14 weeks, pigs were regrouped into 14 groups, and their behaviour recorded for 5h, from which weighted and unweighted networks were constructed. Skin lesions were counted after 24h, 1 week and 2 weeks. Males delivered more aggression, and heavier pigs were involved in more aggression. Betweenness centrality (a network position linking otherwise unconnected individuals) increased with network size and decreased with body weight. Passing the reversal learning test predicted more involvement in unilateral aggression. The current study therefore shows links between cognitive performance and aggression and advances the understanding of social network analysis in the context of animal welfare.