The influence of biopsy site and pregnancy on stable isotope ratios in humpback whale skin

• Published in: Rapid Communications in Mass Spectrometry
• Main Authors: Fraleigh, Devin C., Pallin, Logan J., Friedlaender, Ari S., Barlow, Jay, Henry, Annette E., Waples, Danielle M., Oglesby, Teris, Fleming, Alyson H.
• Other Authors: National Science Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2024
• Subjects: Antarctic; Antarctic Peninsula; Antarc*; Humpback Whale; Megaptera novaeangliae
• Online Access: http://dx.doi.org/10.1002/rcm.9746; https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/pdf/10.1002/rcm.9746

Abstract Rationale Stable isotope analysis (SIA) of free‐swimming mysticetes using biopsies is often limited in sample size and uses only one sample per individual, failing to capture both intra‐individual variability and the influence of demographic and physiological factors on isotope ratios. Methods We applied SIA of δ 13 C and δ 15 N to humpback whale ( Megaptera novaeangliae ) biopsies taken during the foraging season along the western Antarctic Peninsula to quantify intra‐individual variation from repeatedly sampled individuals, as well as to determine the effect of biopsy collection site, sex, and pregnancy on isotope ratios. Results There was substantial variability in δ 13 C from multiple biopsies taken from the same individuals, though δ 15 N was much more consistent. Side of the body (left versus right) and biopsy location (dorsal, anterior, ventral, and posterior) did marginally affect the isotopic composition of δ 15 N but not δ 13 C. Pregnancy had a significant effect on both δ 13 C and δ 15 N, where pregnant females were depleted in both when compared to non‐pregnant females and males. Conclusions These results indicate that isotopic signatures are influenced by multiple endogenous and exogenous factors and emphasize value in accounting for intra‐individual variability and pregnancy status within a sampled population. Placed within an ecological context, the endogenous variability in δ 13 C observed here may be informative for future isotopic analyses.