Data from: Discrimination behavior mediates foraging quality versus quantity trade-offs: nut choice in wild rodents

Discrimination, the ability to distinguish sensory stimuli and respond accordingly, is a critical factor underscoring optimal foraging decisions. Nevertheless, little is known about how mammals discriminate between apparently similar foods of different quality. Here, we compared the foraging behavior of Chinese white-bellied rats, Niviventer confucianus, and Edwards’s long-tailed giant rats, Leopoldamys edwardsi, under natural conditions in the field and in a captive enclosure without predation/competition. We examined the behavioral processes involved in discriminating between sound (i.e., undamaged) and insect larvae-infested nuts of seguin chestnuts (Castanea seguinii) and demonstrated that both rats could discriminate nut quality, where nut examination improved the rats’ success rate at selecting sound nuts. Despite similar extents of discrimination-derived benefit in both settings for each species, differences between species-specific discrimination processes were identified. Chinese white-bellied rats engaged in a higher relative frequency and longer duration of nut examination in the enclosure than in the wild. This indicates that they alter their feeding strategy to trade-off selection for nut quality in captivity for a quantity-driven strategy in the field. In contrast, giant rats showed a consistent relative frequency of nut examination in both experimental settings. Their fixed strategy balanced food quality and quantity primarily to maximize caloric uptake without compromise when faced with predation or competition risk. We posit that this behavioral difference in optimal foraging between rat species is mediated by their differing, size-dependent energetic requirements as well as the higher competition pressure and predation risk faced by the approximately 8 times smaller white-bellied rats.

辨别能力，即区分感官刺激并做出对应反应的能力，是支撑最优觅食决策的关键因素。然而目前学界对哺乳动物如何区分品质迥异但外观相近的食物仍知之甚少。本研究针对中华白腹鼠（Niviventer confucianus）与爱德华长尾巨鼠（Leopoldamys edwardsi），分别在野外自然环境以及无捕食/竞争压力的人工圈养笼舍中，对比二者的觅食行为。本研究以锥栗（Castanea seguinii）的完好坚果与被昆虫幼虫蛀食的坚果为实验材料，探究二者辨别食物品质的行为过程，结果表明两种鼠类均具备辨别坚果品质的能力，且对坚果的探查行为可提升其选择完好坚果的成功率。尽管两个实验环境下，两个物种从辨别行为中获得的收益程度相近，但二者的特异性辨别过程存在差异。中华白腹鼠在圈养环境中，对坚果的探查相对频率更高、持续时间更长，这表明其觅食策略存在调整：在圈养环境中优先权衡坚果品质，而在野外则转向以食物数量为导向的策略。与之相反，爱德华长尾巨鼠在两种实验环境中，对坚果的探查相对频率保持一致。其固定的觅食策略可在面临捕食或竞争风险时，平衡食物品质与数量，在不妥协的前提下最大化热量摄入。本研究推测，两种鼠类在最优觅食行为上的差异，是由二者基于体型的不同能量需求所介导的；同时，体型仅为爱德华长尾巨鼠约1/8的中华白腹鼠，面临着更高的竞争压力与捕食风险。