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 fipsama...@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
Abstract
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
www.icelandic-orcas.com
https://icelandic-orcas.blogspot.com
www.facebook.com/icelandic.orcas
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