Penndorf Julia, Farine Damien R, Martin John M, Aplin Lucy M
Max Planck Institute of Animal Behavior, Radolfzell, Baden-Württemberg, Germany.
Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
R Soc Open Sci. 2025 May 28;12(5):241542. doi: 10.1098/rsos.241542. eCollection 2025 May.
Dominance hierarchies are generally thought to form over time via memory of repeated interactions. Yet dominance hierarchies are also occasionally reported in species with fission-fusion social dynamics, where individuals may encounter large numbers of individuals, leading to incomplete social information. In these cases, three potential mechanisms have been proposed. First, the complex decision-making required could increase selection for social cognition. Second, so-called 'badge-of-status' could evolve as shortcuts. Third, mixed strategies could evolve that rely on memory for interactions with familiars and status signals for strangers. Here, we test these hypotheses in wild sulphur-crested cockatoos (), recording social associations and aggressive interactions of 411 individuals across three neighbouring roosts. We find cockatoos use a twofold social strategy when initiating or reacting to aggression. For familiar individuals, aggressions were initiated or responded to based on differences in dominance rank. However, when facing less familiar individuals, decisions to interact-or respond-were based on body weight, with interactions directed towards, and more likely to respond to, individuals of similar weight. Our results suggest that social knowledge remains an important determinant of aggressive interactions in fission-fusion systems, but that individuals can dynamically incorporate other cues of competitive ability when knowledge is lacking.
优势等级制度通常被认为是随着时间的推移，通过对重复互动的记忆而形成的。然而，在具有裂变-融合社会动态的物种中，也偶尔会报告优势等级制度，在这些物种中，个体可能会遇到大量个体，导致社会信息不完整。在这些情况下，人们提出了三种潜在机制。第一，所需的复杂决策可能会增加对社会认知的选择。第二，所谓的“地位标志”可能会作为捷径而进化。第三，可能会进化出混合策略，即依赖于对熟悉个体互动的记忆和对陌生个体的地位信号。在这里，我们在野生凤头鹦鹉中测试这些假设，记录了三个相邻栖息地中411只个体的社会关联和攻击性行为。我们发现，凤头鹦鹉在发起攻击或对攻击做出反应时采用了双重社会策略。对于熟悉的个体，攻击行为的发起或反应是基于优势等级的差异。然而，当面对不太熟悉的个体时，互动或反应的决定是基于体重做出的，互动针对体重相似的个体，并且更有可能对体重相似的个体做出反应。我们的结果表明，社会知识仍然是裂变-融合系统中攻击行为的重要决定因素，但当缺乏知识时，个体可以动态地纳入其他竞争能力线索。
