When Pigs Fight: Conflict Resolution Among Domestic Pigs

Conflict resolution is an important part of the social lives of many different species, including  parrots, crows, non-human primates, and some wallabies.  It may come as no surprise to learn that pigs have this ability too, as they are also cognitively advanced in other ways. For example, pigs can recognize familiar individuals and objects, show sensitivity to other individuals’ emotions, and proactively respond to others’ distress, all of which play a role in conflict resolution. 

In this study, researchers looked at the ways in which pigs resolve conflicts — both their own conflicts, and conflicts between other individuals. The team focused on a group of 104 pigs living on a farm in Italy. Although the farm raises pigs for slaughter, its mission is to keep them in a natural or semi-natural environment by allowing them to carry out natural behaviors. Over a period of six months, the researchers videotaped the pigs daily, looking for signs of aggression, post-conflict contact between pigs, and anxiety-related behaviors. 

They found three general ways that the pigs resolved conflicts: reconciliation, “triadic solicited contact,” and “triadic unsolicited contact.” In reconciliation, the two pigs involved in the conflict resolve it on their own without the help of a third party. In triadic contacts, a third, uninvolved pig helps to mediate the conflict between the aggressor and victim. This happens either by one of the involved pigs asking the third pig for help (solicited), or by the third pig stepping in independently to help resolve the issue (unsolicited). 

An important contribution of this study is that it shows how pigs choose a conflict resolution strategy in various situations. Specifically, pigs opt for reconciliation more often if they are only weakly related to each other, while third-party pigs mediate conflicts more often if they are closely related to the pig(s) involved in the conflict. This suggests that pigs more generally are able to attach different social values to other pigs depending on their kinship. It also suggests they can regulate their own emotions, help to regulate others pigs’ emotions, and possibly even make their own assessments of a conflict based on how other pigs feel about it. This insight could be helpful for advocates by offering evidence of what some people might consider being “human” traits in pigs, thus making it easier to empathize with pigs’ experiences.

In these ways, the authors argue that pigs may be capable of high-level, cognitively advanced socio-emotional experiences. While advocates have cited the high intelligence of pigs in efforts to protect them, this study adds an additional point of evidence, demonstrating not only that pigs are smart, but also that their emotional lives are rich, fulfilling, and complicated in some of the ways humans’ lives are.

The authors note a few possible limitations of their work. First, only adult pigs were included in the study. Like humans, pigs at different ages might resolve conflicts in different ways. Second, the pigs in the study were domestic and came from only three breeds. Results could be different for other breeds or for wild boars. Next, the composition of the group changed slightly over time, as some pigs were killed during the study period. Finally, male pigs were castrated very young, which could decrease aggression and the frequency of conflicts.

All told, this study bolsters a point advocates have been making for a long time: many species of non-human animals have rich emotional lives that are worth protecting. For better or worse, it seems that humans are more likely to care about other beings they can relate with. To the extent that this study reveals a bit of “humanity” in pigs, animal advocates can use it to create more empathy for them among the general public. This is especially important given the staggering number of pigs slaughtered every year (more than 1.5 billion in 2020). Drastically reducing this number will be crucial to advancing animal protection.