Distributions of Arctic and Northwest Atlantic killer whales inferred from oxygen isotopes
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-f...
Published in: | Scientific Reports |
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Main Authors: | , , , |
Other Authors: | , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Springer Science and Business Media LLC
2021
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Subjects: | |
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 |
Summary: | 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. |
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