Poon Lok, Haag Michael A, Molina Jorge, Crampton William G R
Department of Biology, University of Central Florida, Orlando, Florida, USA.
Departamento de Ciencias Biológicas, Universidad de los Andes, Bogotá, DC, Colombia.
Ecology. 2025 Jun;106(6):e70133. doi: 10.1002/ecy.70133.
Animals continually balance the rewards of activity against the risk of predation. The mere perception of predation risk can trigger cascading effects across "landscapes of fear," from shifts in individual activity to altered community composition. Despite the established role of sensory systems in predator detection, their role in shaping trade-offs between activity and predator avoidance remains underexplored. For many nocturnal species, moonlight-a key driver of predation risk-varies cyclically, offering a unique opportunity to study how sensory capacity influences activity patterns. We studied four species of Neotropical electric fish inhabiting open areas of a shallow, clearwater Amazon stream, where visually oriented nocturnal predators are abundant. These species were similar in size and diet but differed in body mass-adjusted eye size, a commonly used proxy for visual acuity. Using custom-designed loggers to detect and record the continuously emitted, species-specific electrolocation signals of these fish, we monitored each species' foraging activity across a full lunar cycle while simultaneously measuring moonlight illuminance with a low-light radiometer. The two species with the smallest eyes exhibited strong lunar phobia, hiding during moonlit periods and, as a result, sacrificing ~25% of their nocturnal foraging time. They foraged instead during moonless periods, which follow a complex temporal pattern throughout the lunar cycle. In contrast, the species with the largest eyes foraged continuously, likely using vision to detect and evade predators. A species with intermediate-sized eyes showed a canopy-dependent response: foraging normally under semi-open canopy but exhibiting lunar phobia under closed canopy. Active electroreception, the primary sensory modality of electric fish, enables foraging in complete darkness, but its limited range (<10 cm) makes it ineffective for predator detection. Our findings suggest that large-eyed species can detect approaching predators and adopt a "vigilance" strategy, while the poor low-light vision of small-eyed species promotes a "hiding" strategy. These alternative strategies impose distinct metabolic challenges: the opportunity costs of lost foraging time versus the energetic demands of maintaining larger eyes. Overall, our results highlight how sensory adaptations influence critical trade-offs between foraging and predation risk across both spatial and temporal landscapes of fear.
动物不断地在活动的回报与被捕食的风险之间寻求平衡。仅仅是对捕食风险的感知就可能引发跨越“恐惧景观”的连锁反应，从个体活动的变化到群落组成的改变。尽管感觉系统在捕食者检测中已确立了作用，但其在塑造活动与躲避捕食者之间权衡中的作用仍未得到充分探索。对于许多夜行性物种来说，月光——捕食风险的一个关键驱动因素——呈周期性变化，这为研究感觉能力如何影响活动模式提供了独特的机会。我们研究了四种新热带电鱼，它们栖息在一条浅而清澈的亚马逊溪流的开阔区域，那里有大量视觉导向的夜行性捕食者。这些物种在大小和饮食方面相似，但在体重调整后的眼睛大小方面有所不同，眼睛大小通常被用作视力的指标。我们使用定制设计的记录器来检测和记录这些鱼持续发出的、物种特有的电定位信号，在整个月相周期内监测每个物种的觅食活动，同时用低光辐射计测量月光照度。眼睛最小的两个物种表现出强烈的月光恐惧症，在月光照射期间躲藏起来，结果牺牲了约25%的夜间觅食时间。它们改为在无月期间觅食，无月期间在整个月相周期遵循复杂的时间模式。相比之下，眼睛最大的物种持续觅食，可能利用视觉来检测和躲避捕食者。眼睛大小中等的一个物种表现出依赖树冠的反应：在半开放树冠下正常觅食，但在封闭树冠下表现出月光恐惧症。主动电感受是电鱼的主要感觉方式，它能使电鱼在完全黑暗中觅食，但其有限的范围（<10厘米）使其在捕食者检测方面无效。我们的研究结果表明，大眼睛物种能够检测到接近的捕食者并采取“警惕”策略，而小眼睛物种较差的低光视觉则促使其采取“躲藏”策略。这些不同的策略带来了不同的代谢挑战：失去觅食时间的机会成本与维持大眼睛的能量需求。总体而言，我们的结果突出了感觉适应如何在恐惧的时空景观中影响觅食与捕食风险之间的关键权衡。
