Dietary plasticity and broad North Atlantic origins inferred from bulk and amino acid-specific δ15N and δ13C favor killer whale range expansions into Arctic waters

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 2009-2020 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-P..., All details in associated manuscript., , # Dietary plasticity and broad North Atlantic origins inferred from bulk and amino acid-specific δ15N and δ13C favor killer whale range expansions into Arctic waters

[https://doi.org/10.5061/dryad.0zpc8675r](https://doi.org/10.5061/dryad.0zpc8675r)

This dataset includes amino acid specific and bulk stable nitrogen and carbon isotope measurements of lipid extracted from killer whale skin. The skin samples were collected from wild killer whales around Baffin Island, Canada, using standard biopsy techniques. All relevant collection data and permits are provided in the associated manuscript.

## Description of the data and file structure

The Excel file is divided into two pages, one with the amino acid specific data and the other with the bulk tissue data (lipid extracted). Rows are individual whales, while columns are the measurements (d15N and d13C). All data in this Excel file are also presented in the manuscript, either directly or as supplementary information. All analytical details...