Dataset Information

Isotopic niche differs between seal and fish-eating killer whales (Orcinus orca) in northern Norway.

ABSTRACT: Ecological diversity has been reported for killer whales (Orcinus orca) throughout the North Atlantic but patterns of prey specialization have remained poorly understood. We quantify interindividual dietary variations in killer whales (n = 38) sampled throughout the year in 2017-2018 in northern Norway using stable isotopic nitrogen (?15N: 15N/14N) and carbon (?13C: 13C/12C) ratios. A Gaussian mixture model assigned sampled individuals to three differentiated clusters, characterized by disparate nonoverlapping isotopic niches, that were consistent with predatory field observations: seal-eaters, herring-eaters, and lumpfish-eaters. Seal-eaters showed higher ?15N values (mean ± SD: 12.6 ± 0.3‰, range = 12.3-13.2‰, n = 10) compared to herring-eaters (mean ± SD: 11.7 ± 0.2‰, range = 11.4-11.9‰, n = 19) and lumpfish-eaters (mean ± SD: 11.6 ± 0.2‰, range = 11.3-11.9, n = 9). Elevated ?15N values for seal-eaters, regardless of sampling season, confirmed feeding at high trophic levels throughout the year. However, a wide isotopic niche and low measured ?15N values in the seal-eaters, compared to that of whales that would eat solely seals (?N-measured = 12.6 vs. ?N-expected = 15.5), indicated a diverse diet that includes both fish and mammal prey. A narrow niche for killer whales sampled at herring and lumpfish seasonal grounds supported seasonal prey specialization reflective of local peaks in prey abundance for the two fish-eating groups. Our results, thus, show differences in prey specialization within this killer whale population in Norway and that the episodic observations of killer whales feeding on prey other than fish are a consistent behavior, as reflected in different isotopic niches between seal and fish-eating individuals.

SUBMITTER: Jourdain E

PROVIDER: S-EPMC7244801 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Publications

Isotopic niche differs between seal and fish-eating killer whales (Orcinus orca) in northern Norway.

Jourdain Eve E Andvik Clare C Karoliussen Richard R Ruus Anders A Vongraven Dag D Borgå Katrine K

Ecology and evolution 20200408 9

Ecological diversity has been reported for killer whales (Orcinus orca) throughout the North Atlantic but patterns of prey specialization have remained poorly understood. We quantify interindividual dietary variations in killer whales (n = 38) sampled throughout the year in 2017-2018 in northern Norway using stable isotopic nitrogen (δ15N: 15N/14N) and carbon (δ13C: 13C/12C) ratios. A Gaussian mixture model assigned ...[more]

PMID: 32489635

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Project description:Local adaption through ecological niche specialization can lead to genetic structure between and within populations. In the Northeast Pacific, killer whales (Orcinus orca) of the same population have uniform specialized diets that are non-overlapping with other sympatric, genetically divergent, and socially isolated killer whale ecotypes. However, killer whales in Iceland show intrapopulation variation of isotopic niches and observed movement patterns: some individuals appear to specialize on herring and follow it year-round while others feed upon herring only seasonally or opportunistically. We investigated genetic differentiation among Icelandic killer whales with different isotopic signatures and observed movement patterns. This information is key for management and conservation purposes but also for better understanding how niche specialization drives genetic differentiation. Photo-identified individuals (N = 61) were genotyped for 22 microsatellites and a 611 bp portion of the mitochondrial DNA (mtDNA) control region. Photo-identification of individuals allowed linkage of genetic data to existing data on individual isotopic niche, observed movement patterns, and social associations. Population subdivision into three genetic units was supported by a discriminant analysis of principal components (DAPC). Genetic clustering corresponded to the distribution of isotopic signatures, mtDNA haplotypes, and observed movement patterns, but genetic units were not socially segregated. Genetic differentiation was weak (F ST < 0.1), suggesting ongoing gene flow or recent separation of the genetic units. Our results show that killer whales in Iceland are not as genetically differentiated, ecologically discrete, or socially isolated as the Northeast Pacific prey-specialized killer whales. If any process of ecological divergence and niche specialization is taking place among killer whales in Iceland, it is likely at a very early stage and has not led to the patterns observed in the Northeast Pacific.

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Dataset Information

Isotopic niche differs between seal and fish-eating killer whales (Orcinus orca) in northern Norway.

Publications

Isotopic niche differs between seal and fish-eating killer whales (<i>Orcinus orca</i>) in northern Norway.

Similar Datasets

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