Dietary plasticity and broad North Atlantic origins inferred from bulk and amino acid-specific δ

Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic (ECA), where their range expansion associated with declining sea ice have raised questions about the impacts of increasing killer whale predation pressure on Arctic-endemic prey. We assessed diet and distribution of ECA kil...

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Bibliographic Details
Published in:Journal of Animal Ecology
Main Authors: Matthews, Cory J D, Yarnes, Chris T, Lefort, Kyle J, Edkins, Tera L, Kiszka, Jeremy J, Ferguson, Steven H
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2024
Subjects:
Orcinus orca
compound‐specific stable isotope analysis of amino acids
diet
distribution
essential
source
threonine
trophic
Arctic
Baffin Island
Canada
Pacific
Baffin
baleen whales
Killer Whale
North Atlantic
Orca
Sea ice
Killer whale
Online Access:https://doi.org/10.1111/1365-2656.14123
https://pubmed.ncbi.nlm.nih.gov/38956826
Description
Summary:Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic (ECA), where their range expansion associated with declining sea ice have raised questions about the impacts of increasing killer whale predation pressure on Arctic-endemic prey. We assessed diet and distribution of ECA killer whales using bulk and compound-specific stable isotope analysis (CSIA) of amino acids (AA) of 54 skin biopsies collected from 2009 to 2020 around Baffin Island, Canada. Bulk ECA killer whale skin δ15N and δ13C values did not overlap with potential Arctic prey after adjustment for trophic discrimination, and instead reflected foraging history in the North Atlantic prior to their arrival in the ECA. Adjusted killer whale stable isotope (SI) values primarily overlapped with several species of North Atlantic baleen whales or tuna. Amino acid (AA)-specific δ15N values indicated the ECA killer whales fed primarily on marine mammals, having similar glutamic acid δ15N-phenylalanine δ15N (δ15NGlx-Phe) and threonine δ15N (δ15NThr) as mammal-eating killer whales from the eastern North Pacific (ENP) that served as a comparative framework. However, one ECA whale grouped with the fish-eating ENP ecotype based δ15NThr. Distinctive essential AA δ13C of ECA killer whale groups, along with bulk SI similarity to killer whales from different regions of the North Atlantic, indicates different populations converge in Arctic waters from a broad source area. Generalist diet and long-distance dispersal capacity favour range expansions, and integration of these insights will be critical for assessing ecological impacts of increasing killer whale predation pressure on Arctic-endemic species.

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