Witness for resolution: post-conflict quadratic affiliation in semi-free ranging pigs.

In social mammals, post-conflict resolution can involve the reunion of former opponents (reconciliation), spontaneous/solicited post-conflict affiliation of a third party with either opponent (triadic contacts), and affiliation between other individuals (hereafter bystanders; quadratic contacts). Quadratic contacts-possibly informing complex cognitive abilities-have been neglected in post-conflict studies. We investigated quadratic affiliation in semi-free ranging pigs Sus scrofa, at the ethical farm Parva-Domus (Cavagnolo, Italy). Kinship was known. We collected behavioral data on adult pigs (n = 104) via video recordings (43 h) followed by video analyses. Affiliative and anxiety behaviors between bystanders were collected under post-conflict (PC; following a conflict between non-bystanders) and matched-control (MC; no conflict) conditions. Quadratic affiliation was present in pigs, as bystanders affiliated more in PC than MC, and such affiliation was followed by a decrease in the anxiety behaviors of both the interacting bystanders. Thus, quadratic contacts may be partly aimed at reducing one's own anxiety (intrinsic regulation). Quadratic affiliation was highest between closely related bystanders, which suggests that such affiliation may be most effective when close kin is involved. Quadratic affiliation was lowest after reconciliation and spontaneous triadic contacts. This suggests that direct peacemaking between opponents and spontaneous triadic contacts with close kin may most likely replace quadratic affiliation. Hence, pigs can be influenced by the negative events that affect other pigs-but not themselves-and their response may be modulated by social factors. Such non-random quadratic affiliation may point toward the presence of elements of social appraisal abilities in pigs.

Sows' Responses to Piglets in Distress: An Experimental Investigation in a Natural Setting.

Domestic pigs (Sus scrofa) possess complex socio-cognitive skills, and sows show high inter-individual variability in maternal behaviour. To evaluate how females-reared under natural conditions-react to the isolation calls of their own piglets or those of other females, we conducted observations and experimental trials. In January-February 2021, we conducted all-occurrences sampling on affiliation, aggression, and lactation (daily, 7:30-16:30 h) on six lactating and four non-lactating females at the ethical farm Parva Domus (Turin, Italy). The trials (30 s each, n = 37/sow) consisted of briefly catching and restraining a piglet. We recorded the sow response (none/reactive/proactive movement towards the piglet; self-directed anxiety behaviours such as body shaking) before and during the trial and under control conditions. Increased levels of anxiety behaviour in sows were accompanied by an increased frequency of responses. Less aggressive sows and lactating sows showed the highest frequencies of response. Finally, the isolation calls' maximum intensity had an influence on the type of response observed, with higher proactive response frequencies following lower intensity isolation calls. Our results suggest that being under lactation could play a key role in increasing sow response levels and that specific acoustic features may influence the response.

Domestic pigs (Sus scrofa) engage in non-random post-conflict affiliation with third parties: cognitive and functional implications.

In social mammals, conflict resolution involves the reunion of former opponents (aggressor and victim) after an aggressive event (reconciliation) or post-conflict triadic contacts with a third party, started by either opponent (solicited-TSC) or spontaneously offered by the third party (unsolicited-TUC). These post-conflict strategies can serve different functions, including consolation (specifically when TUCs reduce the victim's anxiety). We investigated the possible presence and modulating factors of such strategies on semi-free ranging pigs (Sus scrofa; N = 104), housed at the ethical farm Parva Domus (Cavagnolo, Italy). Kinship was known. Reconciliation was present and mainly occurred between weakly related pigs to possibly improve tolerant cohabitation. Triadic contacts (all present except aggressor TSCs) mostly occurred between close kin. TSCs enacted by victims reduced neither their post-conflict anxiety behaviors nor further attacks by the previous aggressor, possibly because TSCs remained largely unreciprocated. TUCs towards aggressors did not reduce aggressor post-conflict anxiety but limited aggression redirection towards third parties. TUCs towards the victim reduced the victim but not the third-party's anxiety. However, TUCs may also provide inclusive fitness benefits to third parties by benefiting close kin. In sum, pigs engaged in non-random solicited/unsolicited triadic contacts, which suggests that pigs might possess socio-emotional regulation abilities to change their own or others' experience and elements of social appraisal, necessary to detect the emotional arousal of relevant others and (in case of TUCs) take the agency to restore homeostasis.

Play fighting versus real fighting in piglets (Sus scrofa): Similar patterns, different structure.

When animals engage in 'non-serious' fighting (play-fighting) they 'borrow' motor patterns especially from the aggressive context. It may be difficult to distinguish play- and real-fighting. This is particularly true for piglets (Sus scrofa), which can use play-fighting as a substitute for aggression. To check for the structural differences between play- and real-fighting in piglets, we: i) video recorded 496 interactions from three litters (at Parva-Domus extensive ethical farm; Turin, Italy); ii) extracted (by video analyses) duration, patterns, and data on involved individuals; iii) calculated session structural/ecological indices; and iv) compared the indices (play- vs real-fighting). Compared to real-fighting - play-fighting was longer (informing its rewarding nature), more symmetrical (lower asymmetry index) and variable (higher Shannon index). Moreover, play-fighting showed less pattern repetition (lower Repetition Index) and was not more polyadic and evenly distributed (comparable polyadic and Pielou indices). By being longer, and more variable and symmetrical than real-fighting, play-fighting could serve some of its functions such as motor training, social assessment and training for the unexpected. However, play-fighting in piglets did not comply with all the expected play features, possibly because play is a fluid behavioural system that under certain circumstances may escalate into or replace aggression.

Does the Domestication Syndrome Apply to the Domestic Pig? Not Completely.

The 'domestication syndrome' defines a suite of features that domesticated animals possess as the result of the artificial selection operated by Homo sapiens since the Neolithic. An interesting anthropological question is whether such features, including increased tameness and reduced aggression, apply to all domesticated forms. We investigated this issue in the domestic pig (Sus scrofa). We video-recorded and analysed aggression and social play (mostly play-fighting) sessions from piglets (three litters; n = 24) and wild boar hybrids (domestic pig mother x wild boar father; three litters; n = 27) from 6-50 days of age, raised in the same woodland/grassland habitat and extensive farming management (ethical farm 'Parva Domus', Cavagnolo, Torino). Play and aggression session structure was assessed via Asymmetry (AI; offensive/defensive pattern balance), Shannon (H'; pattern variability), and Pielou (J; pattern evenness) indices. We found that piglets played more (especially after the 20th day of life) and engaged in less variable and uniform sessions than wild boar hybrids. Compared to hybrids, piglets showed less variable but more frequent (especially when approaching weaning) and asymmetrical aggressive events. Thus, the domestication syndrome does not seem to fully apply to either social play or aggression, possibly because artificial selection has produced greater tameness of pigs towards humans than towards conspecifics.

Anxiety Behavior in Pigs (Sus scrofa) Decreases Through Affiliation and May Anticipate Threat.

Anxiety is a physio-psychological state anticipating an imminent threat. In social mammals it is behaviorally expressed via displacement activities and buffered via affiliation. Anxiety research on domestic pigs (Sus scrofa) has mostly focused on abnormal/stereotypic behavior associated with intensive farming. We investigated how anxiety is expressed and modulated in semi-free ranging pigs, in natural habitats. Owing to pigs' socio-cognitive complexity, we posited that displacement activities, if such, would increase after a (stressful) intra-group aggression (Prediction 1), be reduced by affiliation (Prediction 2) and influenced by individual/contextual factors (Prediction 3). From 224 videos recorded on adult individuals (Mean ± SD/subject: 4.84 ± 1.85 h) at the "Ethical Farm Parva Domus" (Turin, Italy), we extracted possible displacement activities (vacuum-chewing, scratching/body-rubbing, head/body-shaking, and yawning) in four 3-min conditions: before (BA) and after aggression events, in the absence (AA) or presence (AP) of post-aggression affiliation, and a matched-control (no event; MC). We conducted a minute-by-minute analysis in AE/AA and assessed the effect of subjects' involvement in a conflict (aggressor, aggression's recipient, bystander). All activities were higher in AA than in BA condition-thus being anxiety markers-and all of them decreased to baseline levels in AP, faster compared to AE. Hence, anxiety behavior in pigs was socially buffered. Intriguingly, anxiety behavior was expressed significantly more by bystanders than opponents, which suggests that pigs may be able to anticipate imminent threats. By highlighting how anxiety is managed under extensive farming, this study contributes to the understanding of pig welfare and biology.