In juveniles extreme intraspecies aggression can seem counter-intuitive, as it might endanger their developmental goal of surviving until reproductive stage. Ultimately, aggression can be vital for survival, although the factors (e.g., genetic or environmental) leading to the expression and intensity of this behavior vary across taxa. Attacking (and sometimes killing) related individuals may reduce inclusive fitness; as a solution to this problem, some species exhibit kin discrimination and preferentially attack unrelated individuals. Here, we used both experimental and modeling approaches to consider how physical traits (e.g., size in relation to opponent) and genetic relatedness mediate aggression in dyads of cannibalistic Dendrobates tinctorius tadpoles. We paired full-sibling, half-sibling, and non-sibling tadpoles of different sizes together in an arena and recorded their aggression and activity. We found that the interaction between relative size and relatedness predicts aggressive behavior: large individuals in non-sibling dyads are significantly more aggressive than large individuals in sibling dyads. Unexpectedly, although siblings tended to attack less overall, in size-mismatched pairs they attacked faster than in non-sibling treatments. Using a theoretical model to complement these empirical findings, we propose that larval aggression reflects a balance between relatedness and size where individuals trade-off their own fitness with that of their relatives. Lay SummaryBefore you eat someone, you have to attack them first. Here, we investigated the factors that shape aggression in the cannibalistic tadpoles of the dyeing poison frog. We find that aggression depends on both size and relatedness: when set in pairs, large tadpoles are half as aggressive towards their smaller siblings than to nonsibs. It looks like belonging to the same family provides some protection against aggression, though no one is ever truly safe.

中文翻译：

---

食人物种对亲属的大小依赖性攻击。


对于青少年来说，极端的种内攻击似乎是违反直觉的，因为这可能会危及它们生存到生殖阶段的发育目标。最终，攻击对于生存至关重要，尽管导致这种行为的表达和强度的因素（例如遗传或环境）因类群而异。攻击（有时甚至杀死）相关个体可能会降低包容性适应性；为了解决这个问题，一些物种表现出亲属歧视并优先攻击不相关的个​​体。在这里，我们使用实验和建模方法来考虑物理特征（例如，与对手相关的大小）和遗传相关性如何介导同类相食的 Dendrobatestinctorius 蝌蚪的攻击行为。我们将不同大小的全兄弟、半兄弟和非兄弟蝌蚪在一个竞技场中配对，并记录它们的攻击性和活动。我们发现相对大小和相关性之间的相互作用预测了攻击性行为：非兄弟姐妹中的大个体比兄弟姐妹中的大个体更具攻击性。出乎意料的是，尽管兄弟姐妹总体上攻击较少，但在体型不匹配的配对中，它们的攻击速度比非兄弟姐妹治疗中更快。使用理论模型来补充这些实证研究结果，我们认为幼虫的攻击性反映了相关性和体型之间的平衡，个体在自身适应度与亲属适应度之间进行权衡。总结 在吃掉某人之前，你必须先攻击他们。在这里，我们研究了染色毒蛙同类相食的蝌蚪形成攻击性的因素。 我们发现，攻击性取决于体型和亲缘关系：当成对出现时，大蝌蚪对小蝌蚪的攻击性比对非同胞的攻击性低一半。看起来属于同一个家庭可以提供一些针对侵略的保护，尽管没有人是真正安全的。