Morphological characteristics of harbor seal (Phoca vitulina) whiskers and their use in dietary reconstruction using stable isotope ratios

• Main Authors: Smith, Justin, Karpovich, Shawna, Breed, Greg A, O'Brien, Diane M
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press (a division of Canadian Science Publishing) 2018
• Subjects: harbor seal; Phoca vitulina
• Online Access: http://hdl.handle.net/1807/91217; http://www.nrcresearchpress.com/doi/abs/10.1139/cjz-2017-0309

We investigated whether inferences about harbor seal (Phoca vitulina Linnaeus, 1758) whisker shed status and growth rates based on whisker morphology could improve dietary time series from whisker isotopic profiles. We identified morphometric characteristics of Alaskan harbor seal whiskers, including a smooth root section (SRS) and a bumpy section. The SRS was longer for spring versus fall-collected whiskers and matched the length of fully-grown, shed whiskers. Thus, SRS length can differentiate whisker shed and growth status, and we used it to determine the sequence of whisker shedding by cohort in summer-captured seals. The mean inter-bump length (IBL) correlated with whisker length, potentially providing a proxy for whisker growth rate. We compared carbon isotope ratios (expressed as δ13C values) along the three longest whiskers from 10 harbor seals, using two approaches for converting whisker position to date: (1) a standard growth rate constant based on captive studies and (2) individually adjusted growth rates based on whisker morphology. Intra-individual patterns of whisker δ13C values became more synchronous when expressed by deposition date rather than by position, however, adjusting growth rates based on IBL did not improve synchrony further. These findings suggest that whisker morphology can contribute whisker growth rate and shedding information for dietary reconstruction. The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author.