Third-party interference in agonistic contests entails a deliberate intervention in an ongoing fight by a bystanding individual (third party) and may be followed by post-conflict social behaviour to provide support to a specific individual. The mechanisms behind third-party intervention are, however, still largely understudied. The aim of this study was to investigate third-party interference, with the predictions that (1) the interferer derives benefits from its action by winning a fight, (2) that patterns of intervention depend on familiarity, (3) that dyadic fights last longer than triadic fights, and (4) that interferers engage in non-agonistic social behaviours afterwards. Pre-pubertal pigs (Sus scrofa) (n = 384) were grouped with one familiar and four unfamiliar conspecifics (all non-kin) to elicit contests for dominance rank. Third-party interference was analysed for the first 30 min after grouping, along with the behaviour (nosing or aggression), contest duration, contest outcome, and interferer behaviour after the fight (post-conflict social behaviour). Three types of interference were observed: non-agonistic involvement (nose contact) by the interferer in a dyadic fight; a triadic fight with each of three contestants fighting one opponent at a time; and triadic fights with two opponents jointly attacking the third one (two-against-one fights). The likelihood of a third-party intervention to occur did not depend on the presence of a familiar animal in the fight. However, once intervention was triggered, interferers attacked unfamiliar fight initiators more than familiar ones. Two-against-one fights lasted longer than other triadic fights and occurred more often when both initial contestants were females. Results of 110 triadic fights (out of 585 fights in total) revealed that interferers were more likely to win compared to the initial opponents at equal body weight. The most common post-conflict behaviour displayed by the interferer was agonistic behaviour towards another group member, independently of familiarity. The general lack of discrimination for familiarity suggests interference is not driven by support to familiar individuals in pigs. The results show that intervening in an ongoing fight gives the interferer a high chance of contest success and may be a strategy that is beneficial to the interferer to increase its dominance status.

中文翻译：

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猪（Sus scrofa）冲突中的第三方干预和冲突后行为

第三方对竞争性竞争的干预需要旁观者（第三方）对正在进行的战斗进行故意干预，并且可能会出现冲突后的社会行为，以向特定个人提供支持。然而，第三方干预背后的机制仍然没有得到充分研究。本研究的目的是调查第三方干扰，并预测 (1) 干扰者通过赢得一场战斗而从其行动中获益，(2) 干预模式取决于熟悉程度，(3) 双方的战斗会持续下去比三人争斗持续时间更长，(4) 干扰者随后会进行非对抗性的社会行为。将青春期前的猪 (Sus scrofa) (n = 384) 与 1 个熟悉的同种猪和 4 个不熟悉的同种猪（均为非亲属）分组，以引发对优势等级的竞争。分析分组后前 30 分钟的第三方干扰，以及行为（嗅探或攻击）、比赛持续时间、比赛结果和战斗后干扰者行为（冲突后社交行为）。观察到三种类型的干扰：干扰者在二元战斗中的非对抗性参与（鼻子接触）；三人对战，三名参赛者每次与一名对手交战；以及由两个对手共同攻击第三个对手的三人格斗（二对一格斗）。第三方干预发生的可能性并不取决于战斗中是否存在熟悉的动物。然而，一旦触发干预，干扰者对不熟悉的战斗发起者的攻击比对熟悉的发起者的攻击要多。二对一的打斗比其他三人打斗持续的时间更长，而且当最初的参赛者都是女性时，二对一的打斗更频繁地发生。110 场三方格斗（总共 585 场格斗）的结果显示，在体重相同的情况下，干扰者比最初的对手更有可能获胜。干扰者表现出的最常见的冲突后行为是对另一组成员的攻击行为，与熟悉程度无关。普遍缺乏对熟悉度的区分表明干扰并不是由对猪中熟悉的个体的支持驱动的。结果表明，干预正在进行的战斗给干扰者带来了很大的竞争成功机会，并且可能是有利于干扰者提高其统治地位的策略。