Distributions of Arctic and Northwest Atlantic killer whales inferred from oxygen isotopes

• Published in: Scientific Reports
• Main Authors: Matthews, Cory J. D., Longstaffe, Fred J., Lawson, Jack W., Ferguson, Steven H.
• Other Authors: Natural Sciences and Engineering Research Council of Canada, Nunavut Wildlife Management Board, Canada Research Chairs Program, ArcticNet Network of Centres of Excellence of Canada
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2021
• Subjects: Multidisciplinary; Arctic; Newfoundland; Killer Whale; North Atlantic; Northwest Atlantic; Orca; Orcinus orca; Killer whale
• Online Access: http://dx.doi.org/10.1038/s41598-021-86272-5; http://www.nature.com/articles/s41598-021-86272-5.pdf; http://www.nature.com/articles/s41598-021-86272-5

Abstract Killer whales ( Orcinus orca ) are distributed widely in all oceans, although they are most common in coastal waters of temperate and high-latitude regions. The species’ distribution has not been fully described in the northwest Atlantic (NWA), where killer whales move into seasonally ice-free waters of the eastern Canadian Arctic (ECA) and occur year-round off the coast of Newfoundland and Labrador farther south. We measured stable oxygen and carbon isotope ratios in dentine phosphate (δ 18 O P ) and structural carbonate (δ 18 O SC , δ 13 C SC ) of whole teeth and annual growth layers from killer whales that stranded in the ECA (n = 11) and NWA (n = 7). Source δ 18 O of marine water (δ 18 O marine ) at location of origin was estimated from dentine δ 18 O P values, and then compared with predicted isoscape values to assign individual distributions. Dentine δ 18 O P values were also assessed against those of other known-origin North Atlantic odontocetes for spatial reference. Most ECA and NWA killer whales had mean δ 18 O P and estimated δ 18 O marine values consistent with 18 O-depleted, high-latitude waters north of the Gulf Stream, above which a marked decrease in baseline δ 18 O values occurs. Several individuals, however, had relatively high values that reflected origins in 18 O-enriched, low-latitude waters below this boundary. Within-tooth δ 18 O SC ranges on the order of 1–2‰ indicated interannual variation in distribution. Different distributions inferred from oxygen isotopes suggest there is not a single killer whale population distributed across the northwest Atlantic, and corroborate dietary and morphological differences of purported ecotypes in the region.