[MARMAM] New publication: stable isotope analysis of seal whiskers

Elizabeth McHuron emchuron at ucsc.edu
Fri Oct 26 16:36:02 PDT 2018

Dear colleagues,

My co-authors and I are pleased to announce the publication of the
following paper online in Rapid Communications in Mass Spectrometry

What's in a whisker? Disentangling ecological and physiological isotopic
McHuron, EA, Holser, RR, and DP Costa. https://doi.org/10.1002/rcm.8312

*Rationale:* Stable isotope analysis of keratinized tissues is an
informative tool to quantify foraging ecology that can address questions
related to niche specialization and temporal variation in behavior.
Application of this approach relies on an understanding of tissue growth
and how isotope ratios relate to physiological and ecological processes,
data that are lacking for many species.
*Methods:* We collected paired whisker length measurements from northern
elephant seals to estimate growth and shedding patterns (n = 16). A subset
of seals (n = 5) carried a satellite tag and time-depth recorder across the
7+ month foraging trip following the annual pelage molt. Stable isotopes of
carbon and nitrogen were measured in segments grown across the 6+ week
fasting on land and the subsequent foraging trip; profiles were combined
with growth parameters to timestamp each segment and investigate
relationships with foraging behavior.
*Results:* Whisker loss and initial regrowth primarily occurred during the
annual pelage molt, but newly grown whiskers exhibited active, nonlinear
growth across the foraging trip. δ13C and δ15N values were higher in
segments grown on land than at sea and exhibited a characteristic decline
upon departure from the rookery. There was a relationship between latitude
and longitude and δ15N values, and individual whisker segments grown at sea
could be classified to the correct ecoregion with 81% accuracy.
*Conclusions: *Fasting affected both δ13C and δ15N values and the ability
to exclude these values from ecological investigations is crucial given the
temporal overlap with tissue growth. The rapid decline in isotope ratios
upon departure can be used to isolate portions of the whisker with a strong
physiological signal, even for whiskers with unknown growth histories. The
active growth across the foraging trip combined with the ability to
identify differences in foraging behavior validate the utility of this
approach for addressing ecological questions.

Please don't hesitate to contact me (emchuron at ucsc.edu) with any questions
or for a copy of the manuscript if you do not have access to the journal.

Elizabeth McHuron, Ph.D.
Research Scientist
University of Washington JISAO
115 McAllister Way
Santa Cruz, CA 95060
emchuron at uw.edu <emchuron at ucsc.edu>
emchuron at ucsc.edu
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