Agonistic Behaviour of European Wild Boar (Sus scrofa) in Connection with Farrowing : Welfare Implications of Captivity
2025
Adriansson, Amanda | Björk, Maria
Agonistic behaviour encompasses both aggressive and passive or avoidant behaviours. In wild boars and domestic pigs, this has mainly been studied in piglet-directed contexts. Research on antagonistic behaviours between sows around farrowing is limited despite potentially affecting social relationships, physical and mental health of sows and piglets. While one study reported a decline after farrowing, another reported no significant changes but had limited consideration of individual variance. We addressed this gap using generalised linear mixed models on previously collected data to account for within-individual variance in sows' tendency to perform agonistic behaviours in connection with farrowing, and whether it was influenced by habitat selection. We hypothesised that agonistic interactions would decline after farrowing, aligning with suggestions that isolation is a counter-adaptation against non-maternal infanticide. Significant declines were observed for all agonistic behaviours after farrowing, with one or both of the isolation and sociality phases affecting the behaviour regardless of habitat. Threatening, biting, and butting decreased over a longer timeframe, which could indicate an adaptive value to maintain social bonds, allowing benefits such as communal care. In contrast, responding defensively declined more rapidly, reflecting a temporary shift, allocating resources by reducing defensive behaviour, when non-maternal infanticide risk is reduced by isolation. However, for wild boars in captivity, small enclosure sizes limit such preventive strategies, possibly making the trait maladaptive as the threat of conspecifics remains, potentially reducing maternal success and fitness. We suggest stricter regulation of wild boars' enclosures to ensure better animal welfare standards supporting behavioural needs.
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