Variation in the diet of killer whales Orcinus orca at Marion Island, Southern Ocean

Show simple item record Reisinger, Ryan Rudolf Gröcke, Darren R. Lubcker, Nico McClymont, Erin L. Hoelzel, Rus A. De Bruyn, P.J. Nico 2016-06-21T06:04:47Z 2016-05
dc.description.abstract Diet seems to be a key factor driving diversity and isolation among killer whale populations. Killer whales at Marion Island, Southern Ocean, have been observed preying on seals and penguins but are also know to depredate Patagonian toothfish from longline fishing vessels. However, their diet is poorly known especially when they occur offshore. We analysed carbon and nitrogen stable isotope ratios in 32 skin samples collected from 24 killer whales belonging to 8 social units. Adult males showed higher δ15N values than adult females or subadults, indicating that they occupy a higher relative trophic level. There were no significant differences in δ13C among social units, but δ15N differed significantly and 2 individuals from social units which have been observed depredating Patagonian toothfish had higher δ15N values. The inshore presence of killer whales at Marion Island was a significant predictor of δ13C values, but not of δ15N values. This suggests some foraging north of Marion Island, potentially on lower trophic level prey. We also analysed tissue samples from seal, penguin and Patagonian toothfish prey and used available values for Antarctic fur seals. Results show that killer whales around Marion Island are apex predators, but that they do not feed exclusively on other high trophic level predators such as elephant seals, fur seals, and Patagonian toothfish. Killer whales had δ15N values similar to those of Patagonian toothfish and adult male elephant seals, implying that the diet of killer whales at Marion Island includes some lower trophic level prey such as cephalopods or fishes. en_ZA
dc.description.department Mammal Research Institute en_ZA
dc.description.department Zoology and Entomology en_ZA
dc.description.embargo 2017-05-31
dc.description.librarian hb2016 en_ZA
dc.description.sponsorship The National Research Foundation’s (NRF) Thuthuka and South African National Antarctic programmes, the South African Department of Science and Technology through the NRF, the Mohamed bin Zayed Species Conservation Fund (Project number: 10251290) and the International Whaling Commission’s Southern Ocean Research Partnership. en_ZA
dc.description.uri en_ZA
dc.identifier.citation Reisinger, RR, Gröcke, DR, Lübcker, N, McClymont, EL, Hoelzel, AR & De Bruyn, PJN 2016, 'Variation in the diet of killer whales Orcinus orca at Marion Island, Southern Ocean', Marine Ecology Progress Series, vol. 549, pp. 263-274. en_ZA
dc.identifier.issn 0171-8630 (print)
dc.identifier.issn 1616-1599 (online)
dc.identifier.other 10.3354/meps11676
dc.language.iso en en_ZA
dc.publisher Inter Research en_ZA
dc.rights © 2016 Inter-Research en_ZA
dc.subject Predator en_ZA
dc.subject Stable isotopes en_ZA
dc.subject Carbon en_ZA
dc.subject δ13C en_ZA
dc.subject Nitrogen en_ZA
dc.subject δ15N en_ZA
dc.subject Foraging en_ZA
dc.subject Trophic level en_ZA
dc.title Variation in the diet of killer whales Orcinus orca at Marion Island, Southern Ocean en_ZA
dc.type Postprint Article en_ZA

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