Prey of killer whales (Orcinus orca) in Iceland

Killer whales have a cosmopolitan distribution and as a species are generalists, feeding on a variety of prey. However, local populations tend to specialise on specific prey types. In Icelandic waters, killer whales are generally associated with herring and, thus, have been presumed to be herring specialists. However, recent studies suggest a more complex foraging ecology, possibly including a mosaic of strategies. With increased observational effort in recent years due to research and whale-watching activities, there have been several reports of interactions with different prey, including confirmed predation events. In this study we aimed to summarise the range of potential prey of killer whales observed in Icelandic waters. We report on 12 previously unpublished accounts and review 15 accounts published in the scientific literature or local newspapers, making a total of 27 events where killer whales were observed interacting with actual or potential prey. Thirteen different species, including birds (n = 1), cephalopods (n = 1), fish (n = 5) and marine mammals (n = 6), are reported, although herring is by far the species that killer whales are most often observed interacting with. This study provides the first summary of actual and suspected killer whale prey in Icelandic waters, and contributes towards our understanding of this population's prey preferences. However, describing the diet of individuals/groups was not possible and this study points to a need for continued monitoring to understand the intricacies of killer whale foraging behaviour in this area.