Fishing Technique of Long-Fingered Bats Was Developed from a Primary Reaction to Disappearing Target Stimuli

Behavioral plasticity is a key feature allowing animals to broaden their dietary niche when novel food resources become available, and long-fingered bats provide an appropriate model system to study the underpinnings of behavioral plasticity, since although generally being an insectivorous species, some individuals have been reported to catch fish. Aiming to get insight into the origin of fishing behavior in long-fingered bats, we studied in the field the differences in sensorial and mechanical reactions to insect-like (stationary) and fish-like (temporary) prey stimuli between well-known piscivorous and strictly insectivorous individuals. Both piscivorous and insectivorous individuals exhibited a qualitatively similar reaction to temporary target stimuli (longer and deeper dips and terminal echolocation phase skewed towards buzz I compared to stationary stimuli). Nevertheless, the quantitative differences observed in the sensorial and mechanical features (the intensity of the shift was significantly greater in piscivorous than in insectivorous individuals) show that piscivorous individuals have honed their capture technique likely enhancing the fishing success. Thus, our results suggest that the fishing technique was developed from a primary reaction shared by all long-fingered bats. All individuals seem to be mechanically and sensorially adapted to detect and capture fish, although under appropriate environmental conditions, they would further improve their technique by experience and/or social learning.行为可塑性（behavioral plasticity）是动物在新型食物资源出现时拓展其生态位的关键特征，长指蝙蝠是研究行为可塑性底层机制的理想模型系统：尽管该类群整体为食虫性物种，但已有研究报道部分个体具备捕鱼能力。为深入探究长指蝙蝠捕鱼行为的起源，我们在野外开展对照研究，对比了公认的食鱼性（piscivorous）与严格食虫性（insectivorous）个体对类昆虫（静止）及类鱼类（动态）猎物刺激的感官与机械反应差异。两类个体对动态目标刺激均表现出定性一致的反应：与静止刺激相比，其俯冲深度更深、持续时长更长，且终端回声定位（echolocation）阶段偏向I类蜂鸣（buzz I）。不过，二者在感官与机械特征上存在显著定量差异：食鱼个体的反应偏移强度显著高于食虫个体，这表明食鱼个体已优化其捕猎技巧，进而提升了捕鱼成功率。综上，本研究结果提示，捕鱼技巧源自所有长指蝙蝠共有的基础反应。尽管所有个体均已在机械与感官层面具备探测并捕获鱼类的能力，但在适宜的环境条件下，它们可通过经验积累与/或社会学习进一步精进自身捕猎技艺。