van der Bijl Wouter, Thyselius Malin, Kotrschal Alexander, Kolm Niclas
Department of Zoology/Ethology, Stockholm University, Svante Arrhenius väg 18B, Stockholm 10691, Sweden
Department of Zoology/Ethology, Stockholm University, Svante Arrhenius väg 18B, Stockholm 10691, Sweden.
Proc Biol Sci. 2015 Aug 7;282(1812):20151132. doi: 10.1098/rspb.2015.1132.
Large brains are thought to result from selection for cognitive benefits, but how enhanced cognition leads to increased fitness remains poorly understood. One explanation is that increased cognitive ability results in improved monitoring and assessment of predator threats. Here, we use male and female guppies (Poecilia reticulata), artificially selected for large and small brain size, to provide an experimental evaluation of this hypothesis. We examined their behavioural response as singletons, pairs or shoals of four towards a model predator. Large-brained females, but not males, spent less time performing predator inspections, an inherently risky behaviour. Video analysis revealed that large-brained females were further away from the model predator when in pairs but that they habituated quickly towards the model when in shoals of four. Males stayed further away from the predator model than females but again we found no brain size effect in males. We conclude that differences in brain size affect the female predator response. Large-brained females might be able to assess risk better or need less sensory information to reach an accurate conclusion. Our results provide experimental support for the general idea that predation pressure is likely to be important for the evolution of brain size in prey species.
大脑体积大被认为是对认知益处进行选择的结果，但增强的认知能力如何导致适应性增加仍知之甚少。一种解释是，认知能力的提高会带来对捕食者威胁的更好监测和评估。在这里，我们使用人工选择出大脑大小不同的雄性和雌性孔雀鱼（孔雀花鳉），对这一假设进行实验评估。我们研究了它们作为单条鱼、成对鱼或四条鱼的鱼群对模型捕食者的行为反应。大脑较大的雌性孔雀鱼，而非雄性，花费在进行捕食者检查上的时间更少，这是一种固有风险行为。视频分析显示，成对时大脑较大的雌性孔雀鱼离模型捕食者更远，但当处于四条鱼的鱼群中时，它们对模型捕食者的习惯化速度很快。雄性孔雀鱼比雌性孔雀鱼离捕食者模型更远，但我们再次发现雄性孔雀鱼不存在大脑大小效应。我们得出结论，大脑大小的差异会影响雌性对捕食者的反应。大脑较大的雌性孔雀鱼可能能够更好地评估风险，或者在得出准确结论时需要更少的感官信息。我们的结果为捕食压力可能对猎物物种大脑大小的进化很重要这一普遍观点提供了实验支持。
