Parental aggression can be a costly behaviour and flexible based upon context. While defence of offspring from potential predators has been well studied in the convict cichlid, it is unclear why parents are aggressive towards other parental pairs who are not likely to be offspring predators. In this experiment we explore the aggressive behaviour of pairs towards parental pairs and nonparental individuals using experimental presentations in the field. We found that parental pairs showed more aggressive displays towards other parental pairs than towards nonparental individuals. Bites did not differ between treatments, but there was a sex difference in bites, with males preferring to bite males and females showing no preference. As a higher level of display was observed both in the presence and absence of fry, we also examined the pair response to fry alone. Focal pairs were more aggressive to stimulus fry that were larger than their own fry, indicating that the larger stimulus fry represented a risk to the focal pair, as predicted by previous findings on brood mixing. We conclude that pair aggression towards parental pairs is a means to prevent brood mixing, and the greater aggression shown towards parental pairs suggests that the risk to parental pairs of brood mixing is greater than that of fry predation by nonparental fish.

中文翻译：

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被定罪的慈鲷对的攻击是阻止自然环境中的育雏混合的一种手段

父母的攻击可能是一种代价高昂的行为，并且根据情况灵活。虽然在被定罪的慈鲷中已经很好地研究了保护后代免受潜在捕食者的侵害，但尚不清楚为什么父母会对其他不太可能成为后代捕食者的父母表现出攻击性。在这个实验中，我们使用现场的实验演示来探索对对父母对和非父母个人的攻击行为。我们发现父母对对其他父母对表现出比对非父母个体更具攻击性的表现。不同治疗之间的咬伤没有差异，但咬伤存在性别差异，雄性更喜欢咬雄性，雌性则没有偏好。由于在有和没有鱼苗的情况下都观察到了更高水平的展示，我们还研究了单独炸鱼的配对反应。焦点对对比它们自己的鱼苗大的刺激鱼苗更具攻击性，这表明较大的刺激鱼苗代表了焦点对的风险，正如先前关于育雏混合的发现所预测的那样。我们得出结论，对亲本对的成对攻击是防止育雏混合的一种手段，对亲本对表现出的更大的侵略表明，亲本对育雏混合的风险大于非亲本鱼捕食鱼苗的风险。