PDF(Pubmed)
Abstract：
While various marine predators form associations, the most commonly studied are those between subsurface predators and seabirds, with gulls, shearwaters or terns frequently co-occurring with dolphins, billfish or tuna. However, the mechanisms underlying these associations remain poorly understood. Three hypotheses have been proposed to explain the prevalence of these associations: (1) subsurface predators herd prey to the surface and make prey accessible to birds, (2) subsurface predators damage prey close to the surface and thereby provide food scraps to birds, and (3) attacks of underwater predators lower the cohesion of prey groups and thereby their collective defences making the prey easier to be captured by birds. Using drone footage, we investigated the interaction between Indo-Pacific sailfish (Istiophorus platypterus) and terns (Onychoprion sp.) preying on schooling fish off the eastern coast of the Malaysian peninsula. Through spatio-temporal analysis of the hunting behaviour of the two predatory species and direct measures of prey cohesion we showed that terns attacked when school cohesion was low, and that this decrease in cohesion was frequently caused by sailfish attacks. Therefore, we propose that sailfish created a by-product benefit for the bird species, lending support to the hypothesis that lowering cohesion can facilitate associations between subsurface predators and seabirds.
摘要：
虽然各种海洋捕食者形成协会，最常见的研究是地下捕食者和海鸟之间的研究，海鸥，剪毛水或燕鸥经常与海豚共存，比目鱼或金枪鱼。然而,这些关联的潜在机制仍然知之甚少.已经提出了三个假设来解释这些关联的普遍性：（1）地下捕食者将猎物聚集到地面，并使鸟类可以接近猎物，(2)地下捕食者伤害靠近地面的猎物，从而向鸟类提供食物残渣，（3）水下捕食者的攻击降低了猎物群的凝聚力，从而降低了它们的集体防御能力，使猎物更容易被鸟类捕获。使用无人机镜头，我们调查了印度太平洋旗鱼（Istiophorusplatypterus）和燕鸥（Onychoprionsp。)在马来西亚半岛东海岸捕食养鱼。通过对两种掠食性物种的狩猎行为的时空分析和猎物凝聚力的直接测量，我们表明当学校凝聚力低时，燕鸥会受到攻击，这种凝聚力的下降经常是由旗鱼袭击引起的。因此,我们建议旗鱼为鸟类创造副产品利益，支持降低凝聚力可以促进地下捕食者和海鸟之间的联系的假设。
