Quantity discrimination in a lizard

While foraging or during social interactions, animals may benefit from judging relative quantity. Individuals may select larger prey or a patch with more food and likewise, it may pay to track the number and type of individuals and social interactions. We tested for spontaneous quantity discrimination in the gidgee skink (Egernia stokesii), a family-living lizard. Lizards were presented with food quantities differing in number or size and selected the larger quantity of food items when they differed in number, but not when items differed in size. We show, for the first time, superior spontaneous discrimination of items differing in number over size in a lizard species which contrasts with previous findings. Our simple method, however, did not include controls for the use of continuous quantities and further tests are required to determine the role of such information during quantity discrimination. Our results provide support for use of the parallel individuation system for the discrimi...在觅食或社交互动过程中，动物通过判断相对数量可获得适应性收益。个体可选择体型更大的猎物或食物丰度更高的觅食斑块；同理，追踪同类的数量、类群以及社交互动行为亦具备演化优势。本研究针对群居蜥蜴吉吉石龙子（Egernia stokesii）的自发数量辨别能力展开了实验探究。研究人员向石龙子展示数量或尺寸存在差异的食物，结果表明：当食物仅数量不同时，石龙子会优先选择数量更多的食物；而当食物仅尺寸存在差异时，石龙子则无明显偏好。本研究首次在蜥蜴类物种中发现，相较于尺寸差异的刺激，该物种能更出色地自发辨别数量差异的食物，这与既往相关研究结论相悖。不过，本研究采用的简易实验方案未设置连续数量信息的对照组，因此仍需开展进一步实验，以明确此类信息在数量辨别过程中的具体作用。本研究结果为并行个体化系统（parallel individuation system）在数量辨别中的应用提供了实验依据，相关论述暂未完整呈现。