[MARMAM] New publication: Cetacean Skeletons Demonstrate Ecologically Relevant Variation in Intraskeletal Stable Isotopic Values

Kerri J. Smith smithkerrij at gmail.com
Wed Jun 3 06:19:02 PDT 2020

Dear all,

We are pleased to share our recent publication on carbon and nitrogen
isotope variation in cetacean skeletons.

Smith KJ, Sparks JP, Timmons ZL and Peterson MJ (2020) Cetacean Skeletons
Demonstrate Ecologically Relevant Variation in Intraskeletal Stable
Isotopic Values. *Front. Mar. Sci.* 7:388. doi: 10.3389/fmars.2020.00388

Conservation science requires quickly acquiring information and taking
action in order to protect species at risk of extinction. Stable isotope
measurements are one way to rapidly gather data regarding species’ foraging
ecology and habitat use, and passively collected samples limit additional
stress to at-risk species. For these samples to be useful, however, we must
know how representative they are of the stable isotope ratios of the entire
organism. Bone tissue, often stored in museum collections or research
centers, may be the most readily available tissue from rare, endangered, or
extinct vertebrates, but using bone requires practitioners to understand
intraskeletal stable isotope variation. We sampled the same eight skeletal
elements from 72 cetacean skeletons from 14 species to evaluate
intraskeletal variation in carbon and nitrogen isotope values. We found
considerably more variation than anticipated. Carbon intraskeletal ranges
varied from 0.4 to 7.6‰, with 84.7% (*n* = 61) of skeletons having a range
>1‰, and 55.5% (*n* = 40) exhibiting a range >2‰. Similarly, nitrogen
intraskeletal ranges varied from 0.4 to 5.2‰, with 59.7% (*n* = 43) of
skeletons exhibiting a range >1‰, and 15.3% (*n* = 11) with a range >2‰.
There were differences in which bones contributed most to intraskeletal
variation; however, we advise against using humeri and mandibles as these
bones presented the most consistent trends in deviation from the
intraskeletal means for both isotopes. The large intraskeletal variation we
observed is likely due to changes in foraging behavior or habitat use being
reflected differently in bone isotope ratios due to differences in bone
turnover rates. We suggest that for cetaceans, intraskeletal carbon isotope
ranges >1‰ and nitrogen ranges >2‰ are ecologically relevant, and that
using different bones from animals of the same population may produce false
positive differences in foraging behavior or habitat within the population
if intraskeletal variation is not considered. Future studies should use the
same bones from each animal and conduct species-specific analyses of
intraskeletal variation, if possible, when using specimens of opportunity.
Failure to consider this variation could lead to erroneous conclusions
regarding a species range or key habitats, jeopardizing conservation


*--Kerri J. Smith, Ph.D.*
Postdoctoral Researcher - Baylor University
Research Fellow - Smithsonian Institution
Website <https://kerrijsmith.wordpress.com/>

“The love for all living creatures is the most noble attribute of man.”
-Charles Darwin
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