[MARMAM] New publication on foraging ecology of sperm whales based on stable isotope analyses

Marta Guerra martaguerra87 at gmail.com
Thu Mar 19 17:59:11 PDT 2020

Dear MARMAM subscribers,

My colleagues and I would like to announce the publication of the following
article in Marine Ecology Progress Series:

*'Stable isotope analyses reveal seasonal and inter-individual variation in
the foraging ecology of sperm whales'*

Marta Guerra, Lucy Wing, Stephen Dawson, William Rayment


Studying inter-individual variation in foraging by top predators is key for
understanding the ecology of their populations, while knowledge of seasonal
variability in foraging helps explain temporal changes in habitat use and
ecological role. We investigated the inter-individual and seasonal
differences in stable isotope ratios of sperm whales *(Physeter
macrocephalus)* in the temperate foraging ground of the Kaikōura Canyon,
New Zealand. Isotope ratios of carbon and nitrogen were measured in 107
samples of sloughed skin from 37 individual males with a wide range of
residency patterns and body lengths, sampled over four summers and three
winters. Variability in individual isotope ratios was analysed with
generalised additive mixed models. The whales’ residency patterns, but not
body size, accounted for most heterogeneity of δ13C and δ15N. Specifically,
whales that visited Kaikōura occasionally had more diverse and lower
isotope ratios than more frequent visitors (by* ca. *-1‰ δ13C and -2‰ δ15N),
likely reflecting a range of foraging habitats further offshore and/or
south of Kaikōura Canyon. We suggest that these patterns reflect
differences in large-scale foraging patterns within the population. In
addition, whales sampled in winter had significantly lower values of δ13C
than whales sampled in summer (by* ca. *-0.5‰), indicating seasonal
differences in the use of food resources. Our results provide new insights
into foraging patterns of sperm whales, and highlight the value of
accounting for individual differences in the ecology of top predators.
The article can be accessed via https://doi.org/10.3354/meps13255
(subscription only), or you can email me at marta.guerra at otago.ac.nz for a
copy of the pdf.

Best wishes,
Marta Guerra
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