Data from: Concede or clash? solitary sharks competing for food assess rivals to decide.

To adapt to their environment, organisms can either directly interact with their surroundings or use social information, namely information provided by neighbouring individuals. Social information relates to the external features of surrounding peers, and little is known about its use by solitary species. Here, we investigated the use of social cues in a solitary marine predator by creating artificial aggregations of free-ranging sicklefin lemon sharks (Negaprion acutidens). Using a novel monitoring protocol, we analysed both dominance interactions and tolerance associations between sharks competing for food in relation with the number, the morphology and the behaviour of rivals. Sharks produced more agonistic displays and spent more time around the bait as competitors were more abundant. Moreover, the morphological attributes of competitors had very limited influence on the structure of shark social interactions. Instead, sharks appeared to establish tolerance relationships with competitors according to their individual behaviour. Furthermore, the more two sharks were observed together at a given study site, the fewer agonistic interactions they exchanged. We discuss these findings as evidence of the use of social cues in a non-gregarious predatory species and suggest directions for future research.为适应栖息环境，生物可通过两种途径与环境产生交互：直接与周遭环境互动，或是借助社会信息（social information）——即由邻近个体所提供的各类信息。社会信息与周遭同类的外部特征相关，目前学界对独居物种如何利用此类信息仍知之甚少。本研究以独居海洋捕食者为对象，通过构建自由活动的犁鳍柠檬鲨（Negaprion acutidens）人工聚集群，探究该物种对社会线索（social cues）的利用情况。研究采用新型监测方案，针对鲨鱼争夺食物时的支配互动与容忍关联展开分析，探究其与竞争者数量、形态特征及行为模式之间的关联关系。结果显示，随着竞争者数量增加，鲨鱼会展现出更多争斗展示行为，且在饵料区域停留的时长也随之增加。此外，竞争者的形态特征对鲨鱼社会互动的结构影响极为有限。与之相反，鲨鱼似乎会依据竞争者的个体行为来建立彼此间的容忍关系。进一步而言，在同一研究区域内，被观测到共同出现的频次越高的两条鲨鱼，彼此间发生的争斗互动就越少。本研究将上述发现作为非群居捕食性物种利用社会线索的实证依据展开讨论，并为后续研究指明了可行方向。