First longitudinal study of seal-feeding killer whales (Orcinus orca) in Norwegian coastal waters.

• Published in: PLOS ONE
• Main Authors: Eve Jourdain, Dag Vongraven, Anna Bisther, Richard Karoliussen
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2017
• Subjects: Medicine; R; Science; Q; Norway; Killer Whale; Orca; Orcinus orca; Phoca vitulina; Killer whale
• Online Access: https://doi.org/10.1371/journal.pone.0180099; https://doaj.org/article/e1cad6db35514ae5b68e8beec7147b31

Killer whales (Orcinus orca) have been documented preying on either fish or marine mammals in several regions, suggesting that this odontocete species has the ability to specialize on different types of prey. Off Norway, killer whales have been shown to rely on the Atlantic herring (Clupea harengus) as a main prey resource. Infrequent observations have revealed seals as an additional component of their diet, yet the extent of predation on marine mammals has remained largely unknown. Here, we present the findings of 29 years of photographic and observational data on seal-feeding killer whale groups identified in Norwegian coastal waters. Four groups have been observed preying and feeding on seals over several years, taking both harbor (Phoca vitulina) and grey (Halichoerus grypus) seals. These stable groups are shown to adopt small group sizes, were typically observed in near-shore areas and were not encountered on herring wintering grounds. Behavioral and social traits adopted by these groups are similar to those of pinniped-feeding killer whales from other regions. The potential ecological reasons and the extent of such prey specializations are discussed.