[MARMAM] New study investigating the isotopic niche of Icelandic killer whales

Filipa Samarra fipsamarra at gmail.com
Sun Feb 5 04:13:04 PST 2017

Dear colleagues,

We are happy to announce the publication of the following paper in 
Marine Ecology Progress Series:

Intra-population variation in isotopic niche in herring-eating killer 
whales off Iceland
Filipa I. P. Samarra, Morgana Vighi, Alex Aguilar and Gísli A. Víkingsson
Marine Ecology Progress Series 564: 199-210

The paper is available online at 
http://www.int-res.com/abstracts/meps/v564/p199-210/ or you can contact 
me at fipsamarra at gmail.com for a reprint or if you have any questions.

This study is part of the Icelandic Orca Project, a long-term research 
project dedicated to the study of killer whales in Iceland. You can find 
out more about the project on www.icelandic-orcas.com

Among-individual variation in dietary preferences can impact community 
dynamics and be a driving force for evolutionary divergence, although it 
can be difficult to assess in free-ranging marine mammal populations. In 
this study, we investigate the existence of variation in isotopic niche 
within a population of putative herring-specialist killer whales. 
Isotopic ratios of carbon and nitrogen were measured in 67 skin biopsy 
samples from 56 individual killer whales, sampled in herring 
overwintering (winter) grounds and spawning (summer) grounds in Iceland 
when the whales were presumably feeding on herring. Whales that appeared 
to follow herring year round (n = 31) had lower δ15N values, consistent 
with a diet predominantly composed of herring. This supports the 
existence of herring specialists in the population. In contrast, whales 
that were only photo-identified either in winter or in summer (n = 25) 
had larger variation in δ15N values. A discriminant function analysis 
clearly distinguished between putative herring specialists and whales 
seasonally travelling to Scotland in summer (n = 3), which exhibited 
distinctly larger δ15N values indicative of a diet including higher 
trophic level prey. This study shows that herring-eating killer whales 
in Iceland exhibit intra-population ecological variation, whereby 
individuals or groups differ in the proportional contribution of 
different prey items to their diet. This variation occurs in the absence 
of social and, potentially, reproductive isolation. Although further 
information will be required to assess the degree of structuring within 
the population, such heterogeneity should be taken into account in 
future conservation and management plans.

Best regards,

Filipa Samarra
Postdoctoral Researcher
Marine Research Institute
Skúlagata 4
121 Reykjavík, Iceland
Tel: +354-5752082

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