A post-war study on pigs: How to mediate a fight? How to make peace?

Domestic pigs are a subspecies of wild boars that were domesticated by humans. In ancient times, they were also called "pigs", "porks", "pigs", etc.

When people mention pigs, they often think of the lazy and gluttonous "Pig Brother".

However, apart from the label of "gluttonous and lazy", pigs are also very docile and cute animals .

However, pigs are social animals after all. Even if they have a good temper, conflicts may break out between pigs over their own interests .

Previous research has shown that one of the main challenges for social animals is managing inevitable resource conflicts within the group, which, if not resolved, can lead to the group breaking up.

For social animals, conflict resolution occurs either by the aggressor and victim reuniting after the conflict and reconciling (voluntary reconciliation) or by involving third-party bystanders, thereby reducing further aggressive behavior or anxiety following injury.

These conflict resolution strategies are important for maintaining balance in social animal groups and reducing anxiety in victims.

However, there has been no research on how domestic pigs make peace after a conflict and how third parties mediate.

In a new study, a research team from the University of Turin in Italy revealed the complex social groups formed by domestic pigs and how they resolve conflicts.

They found that when two domestic pigs were fighting, a bystander could intervene to either reduce the number of attacks by the attacker or help reduce the victim's anxiety.

The related research paper, titled “Domestic pigs (Sus scrofa) engage in non-random post-conflict affiliation with third parties: cognitive and functional implications”, has been published in the scientific journal Animal Cognition.

During this research, the research team carefully studied the behavior of 104 domestic pigs after conflicts occurred, identified the generations of most domestic pigs based on their breed, size and markings, and conducted genetic tests on 31 domestic pigs of different generations to determine the kinship of the entire group.

They observed and recorded interactions between different pigs, as well as aggressive behaviors such as head-butting, pushing, biting and arching, between June and November 2018.

Image: A conflict broke out between two domestic pigs. (GIF source: Animal Cognition)

After each aggressive conflict, they also continued to observe the pigs' behavior for the next three minutes and recorded their gender, kinship and age.

They found that both aggressors and victims exhibited conciliatory behaviors , such as nudging each other’s noses, snuggling, and resting their heads on each other. Furthermore, both aggressors and victims initiated conciliatory behaviors after a conflict had occurred.

However, the proportion of reconciliation was significantly higher in distantly related domestic pigs compared to more closely related domestic pigs .

(Injured pig: Brothers will not be forgiven easily~)

The research team explains that domestic pigs may evaluate different relationships based on what they can provide, such as social support.

Conflicts that break out between close relatives (full, half, and half kin) may be less harmful to the social group because these relationships can be seen as safer ones.

However, distantly related or unrelated domestic pigs were more likely to engage in conciliatory behaviors after conflict to ensure they still received social support and food within the group .

So what does a domestic pig do when it sees a conflict break out between other domestic pigs? And why do they do what they do?

The research team noted that the specific behavioral differences mainly depended on which of the conflicting parties the bystander pigs approached and contacted .

If the bystander pigs approached and engaged the victim , there was a significant reduction in anxiety-related behaviors observed in the victim, including trembling, scratching, chewing and yawning, although the amount of aggressive behavior did not change.

Image: Bystanders comfort the victim. (GIF source: Animal Cognition)

However, if a bystander approached the attacker , the number of aggressive behaviors toward the victim decreased significantly.

In addition, domestic pigs that are watching are more likely to intervene if one of the conflicting parties is a close relative or a close friend .

After a conflict, victims' attempts to approach and engage with bystanders had no effect on reducing the occurrence of anxious behaviors or the likelihood of being attacked again.

It turned out that bystanders did not respond to the victims approaching them in 95.2% of the cases (42 cases).

This suggests that domestic pigs value certain relationships and are more likely to support close relatives .

In addition, the research team also emphasized that this study only involved a group of adult domestic pigs and may not be representative of all pig groups. In future work, they may investigate whether these conflict resolution strategies work in other situations.

However, the behavior of domestic pigs in reconciling or persuading others after conflict suggests that they may have some social emotion regulation ability to change their own feelings or those of others in group conflicts.

References:

https://link.springer.com/article/10.1007/s10071-022-01688-4

https://www.youtube.com/watch?v=3fe9mkpd5VY&ab_channel=NPGPress

https://www.youtube.com/watch?v=KYkrnUUUat4&ab_channel=NPGPress