Behavioural responses of animals are often placed conceptually along some axis characterized by the extremes, e.g. bold versus shy or timid. Ecological and evolutionary pressures can be associated with increased frequencies of different behavioural patterns that are also subject to intrinsic factors such as differing metabolic requirements or cognitive abilities. We exposed individual wild-caught juvenile bluegill, Lepomis macrochirus, to kairomones from predatory northern pike, Esox lucius, or to lake water controls during a Z-maze arena assay commonly used to assess relative levels of boldness and exploratory behaviours. Fish were subsequently lethally sampled for liver and brain mass to obtain estimates of relative body condition (hepato-somatic index, HSI) and cognitive capacity (brain-somatic index, BSI), as well as the state of the gallbladder, to test for relationships between these indices and observed boldness-related behaviours. Using principal components analysis (PCA) we identified a boldness–exploration syndrome in bluegill independent of chemical treatment and body metrics where bolder fish emerged from a start chamber in less time, travelled farther through the maze and crossed more lines than less bold fish. Bluegill exposed to kairomones were bolder on average than their counterparts in the control treatment independent of body metrics, suggesting that elevated risk levels indicated by predator kairomones can elicit behavioural responses consistent with boldness, exploration and risk taking. The role of relative cognitive ability in the expression of boldness and exploration is equivocal and may be resolved through repeated assays on individuals at different risk levels.

中文翻译：

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捕食者 kairomones 在幼年蓝鳃鱼中引发大胆的探索行为，Lepomis macrochirus

动物的行为反应通常沿着一些以极端为特征的轴在概念上放置，例如大胆与害羞或胆怯。生态和进化压力可能与不同行为模式的频率增加有关，这些行为模式也受内在因素的影响，例如不同的代谢需求或认知能力。我们在通常用于评估大胆和探索行为的相对水平的 Z 迷宫竞技场试验中，将个体野生捕获的蓝鳃鱼幼鱼暴露于来自掠食性北梭鱼、Esox lucius 的 kairomones 或湖水控制。随后对鱼的肝脏和大脑质量进行致命采样，以获得相对身体状况（肝-体指数，HSI）和认知能力（脑-体指数，BSI）的估计值，以及胆囊的状态，以测试这些指数与观察到的大胆相关行为之间的关系。使用主成分分析 (PCA)，我们确定了蓝鳃鱼的大胆探索综合征，与化学处理和身体指标无关，其中较大胆的鱼在更短的时间内从起始室出现，穿过迷宫走得更远，穿过的线比不那么大胆的鱼多。在独立于身体指标的控制治疗中，暴露于 kairomones 的 Bluegill 平均比它们的对应物更大胆，这表明捕食者 kairomones 指示的升高的风险水平可以引发与大胆、探索和冒险一致的行为反应。