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

PLoS One. 2017 Jun 30;12(6):e0180099. doi: 10.1371/journal.pone.0180099. eCollection 2017. Jourdain E1, Vongraven D2, Bisther A3, Karoliussen R1. Author information Abstract 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. PMID: 28666015 PMCID: PMC5493372 DOI: 10.1371/journal.pone.0180099 Free PMC Article Share on FacebookShare on TwitterShare on Google+ Images from this publication.See all images (6)Free text Fig 1Fig 2Fig 3Fig 4Fig 5Fig 6 LinkOut - more resources