Sea Mammal Research Unit, University of St Andrews, St Andrews, Fife KY16 8LB, UK
Centre d'Etudes Biologiques de Chizé, CNRS, 79360 Villiers en Bois, France.
J Exp Biol. 2020 May 19;223(Pt 10):jeb222810. doi: 10.1242/jeb.222810.
Bioluminescence, which occurs in approximately 80% of the world's mesopelagic fauna, can take the form of a low-intensity continuous glow (e.g. for counter-illumination or signalling) or fast repetitions of brighter anti-predatory flashes. The southern elephant seal (SES) is a major consumer of mesopelagic organisms, in particular the abundant myctophid fish, yet the fine-scale relationship between this predator's foraging behaviour and bioluminescent prey remains poorly understood. We hypothesised that brief, intense light emissions should be closely connected with prey strikes when the seal is targeting bioluminescent prey that reacts by emitting anti-predator flashes. To test this, we developed a biologging device containing a fast-sampling light sensor together with location and movement sensors to measure simultaneously anti-predator bioluminescent emissions and the predator's attack motions with a 20 ms resolution. Tags were deployed on female SES breeding at Kerguelen Islands and Península Valdés, Argentina. light levels in combination with duration of prey capture attempts indicated that seals were targeting a variety of prey types. For some individuals, bioluminescent flashes occurred in a large proportion of prey strikes, with the timing of flashes closely connected with the predator's attack motion, suggestive of anti-predator emissions. Marked differences across individuals and location indicate that SES do exploit bioluminescent organisms but the proportion of these in the diet varies widely with location. The combination of wideband light and acceleration data provides new insight into where and when different prey types are encountered and how effectively they might be captured.
生物发光存在于全球约 80%的中层水域动物中，其形式可以是低强度的连续发光（例如用于对抗照明或信号）或更快的更亮的抗捕食闪光重复。南方象海豹（SES）是中层水域生物的主要消费者，特别是大量的磷虾鱼类，但这种捕食者的觅食行为与生物发光猎物之间的精细关系仍然知之甚少。我们假设，当海豹以生物发光的猎物为目标时，短暂而强烈的光发射应该与猎物的攻击密切相关，因为猎物会发出抗捕食闪光。为了验证这一点，我们开发了一种生物标记设备，其中包含一个快速采样的光传感器以及位置和运动传感器，以 20 毫秒的分辨率同时测量抗捕食生物发光发射和捕食者的攻击动作。标签被部署在位于凯尔盖朗群岛和阿根廷的瓦尔迪兹半岛的雌性 SES 繁殖地。光水平与猎物捕获尝试的持续时间结合起来表明，海豹以各种猎物类型为目标。对于一些个体，生物发光闪光出现在很大比例的猎物攻击中，闪光的时间与捕食者的攻击动作密切相关，这表明存在抗捕食者的发光。个体和地点之间的明显差异表明，SES 确实利用了生物发光生物，但这些生物在饮食中的比例因地点而异。宽带光和加速度数据的结合提供了新的见解，了解不同的猎物类型在何处以及何时出现，以及它们被捕获的效率如何。
