Fatty acid proportions in North Atlantic killer whales from the Canadian Arctic to Arctic Norway (2008-2021)

Scientists have been studying the feeding habits of killer whales for decades, but there is still much to learn. Recent studies suggest that killer whales from Norway and Iceland mainly feed on fish, while those from Greenland and Canada eat marine mammals. Most of the previous studies that looked at North Atlantic killer whale diets relied on observation at sea. And while observing a predation event is always useful and indicates that a specific species have been consumed at some point, we cannot really conclude on the long-term dietary habits of various populations. This is especially true for remote populations (think the Canadian Arctic and Greenland), because these observation events cannot happen year-long. To better understand what these predators eat, scientists can use time-integrated dietary tracers like stable isotopes or fatty acid signature analysis. These methods provide information about a predator's long-term diet, especially when killer whales are in isolated areas and impossible to observe year-long. That's where quantitative fatty acid signature analysis (QFASA) comes in. This statistical model allows scientists to estimate the relative contributions of each prey species to a predator's diet. This method involves measuring the lipid composition in the killer whales and their potential prey, enabling the team to estimate the exact proportion of different prey in the whales' diets. We measured this fatty acid proportions in killer whales using our newly validated quantitative fatty acid signature analysis (QFASA) approach on nearly 200 killer whales to model their diets across the 5,000 km span of the North Atlantic.

数十年来，科学家始终致力于研究虎鲸（killer whales）的摄食习性，但仍有诸多未解之处。近期研究表明，挪威与冰岛海域的虎鲸主要以鱼类为食，而格陵兰及加拿大海域的虎鲸则以海洋哺乳动物为主要猎物。此前绝大多数针对北大西洋海域虎鲸食性的研究，均依赖海上实地观测手段。尽管观测捕食事件具备参考价值，能够证明虎鲸在特定时刻捕食了某一物种，但我们无法借此准确推断不同虎鲸种群的长期食性。对于地处偏远的虎鲸种群（例如加拿大北极海域与格陵兰海域的种群）而言，这一局限尤为突出——因为无法全年开展实地观测工作。为更全面地了解这些顶级捕食者的食性，科学家可采用时间整合型食性示踪技术，例如稳定同位素分析法或脂肪酸特征分析（fatty acid signature analysis）。这类方法能够反映捕食者的长期摄食情况，尤其适用于虎鲸栖息于偏远海域、无法全年开展观测的场景。定量脂肪酸特征分析（quantitative fatty acid signature analysis, QFASA）正是解决这一问题的理想方法。该统计模型可帮助科学家估算每种猎物物种在捕食者饮食中的相对贡献占比。该方法通过测定虎鲸及其潜在猎物的脂质组成，使研究团队能够精准估算不同猎物在虎鲸饮食中的具体比例。本研究团队采用经过全新验证的定量脂肪酸特征分析（QFASA）方法，对近200头虎鲸体内的脂肪酸比例进行了测定，以此构建覆盖北大西洋5000公里海域范围的虎鲸食性模型。