Feeding Ecology

Killer whales in Norway feed on a variety of prey including fish and marine mammals. Feeding habits influence the whales’ contaminants loads, and plasticity in diet shapes their capacity to adapt to changing habitats. The aim of this project is to identify patterns of dietary habits and variations at the individual and group levels. We combine visual observations collected from unmanned aerial vehicles (drone) of predation events and molecular techniques applied to prey remains collected from the surface, to identify target prey species. We also use dietary markers such as fatty acids and stable isotopic ratios in biopsy samples to evaluate long-term feeding habits of sampled individuals. Multi-sensor camera tags attached with suction cups is used to quantify activity budgets and prey profitability. So far, we have confirmed herring, mackerel, lumpfish, seal and porpoise as part of Norwegian killer whales’ diet. While some groups appear to be herring-specialists, others seem to switch seasonally or opportunistically to feeding on other prey. A subset of groups feed on marine mammals in addition to fish; these whales carrying four times higher levels of toxins than others known to be exclusive fish-eaters. To date, there is no evidence of mammal-specialized killer whales in Norway. Identify feeding behaviors and food sources will help tracking sources of contamination and assessing Norwegian killer whales’ resilience capacity to increasingly disturbed natural habitats.