Data from: Initiators, leaders and recruitment mechanisms in the collective movements of damselfish

Explaining how individual behavior and social interactions give rise to group-level outcomes and affect issues such as leadership is fundamental to the understanding of collective behavior. Here we examined individual and collective behavioral dynamics in groups of humbug damselfish both before and during a collective movement. During the predeparture phase, group activity increased until the collective movement occurred. Although such movements were precipitated by one individual, the success or failure of any attempt to instigate a collective movement was not solely dependent on this initiator’s behavior but on the behavior of the group as a whole. Specifically, groups were more active and less cohesive before a successful initiation attempt than before a failed attempt. Individuals who made the most attempts to initiate a collective movement during each trial were ultimately most likely to lead the collective movement. Leadership was not related to dominance but was consistent between trials. The probability of fish recruiting to a group movement initiative was an approximately linear function of the number of fish already recruited. Overall, these results are consistent with nonselective local mimetism, with the decision to leave based on a group’s, rather than any particular individual’s, readiness to leave.

阐释个体行为与社会互动如何催生群体层面结果，并影响领导力等议题，是理解集体行为的核心基础。本研究针对三斑宅泥鱼（humbug damselfish）群体在集体移动发生前后的个体与集体行为动态展开了考察。在集体移动启动前的阶段，群体活动水平持续上升，直至集体移动正式启动。尽管这类集体移动由某一个体率先促成，但发起集体移动的尝试能否成功，并非仅取决于该发起者的行为，而是由整个群体的行为共同决定。具体而言，相较于发起尝试失败的前置阶段，发起尝试成功的群体在该阶段表现出更高的活动水平与更低的群体凝聚力。在每一轮实验试次中，最频繁发起集体移动尝试的个体，最终也最有可能成为集体移动的领导者。群体领导力与个体的支配地位无关，但在不同实验试次间具有一致性。响应集体移动发起倡议的鱼类个体占比，与已响应招募的鱼类数量大致呈线性相关关系。综合来看，本研究结果与非选择性局部模仿（nonselective local mimetism）理论相符：个体是否选择离群的决策，取决于整个群体的离群准备状态，而非某一特定个体的离群意愿。