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.