ABSTRACT Stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) are widely used to study the feeding ecology of cetaceans, as they provide critical insights into diet and migratory behaviors. Lipids in tissues may bias the interpretation of δ 13 C. Because of this, lipids need to be extracted before measuring stable isotope ratios, but their removal may alter δ 15 N values. Using nearly 900 skin samples of five cetacean species, this study examined the impact of lipid extraction (Folch method) on skin δ 15 N values and developed mathematical corrections for these effects. The mathematical corrections were then validated with three species sampled in the same or other environments. Lipid extraction increased δ 15 N values in all species, albeit by a variable amount. This effect was accurately predicted by both species‐specific and multi‐species linear relationships. The proposed mathematical corrections across species and environments offer a cost‐effective alternative to analysis of separate aliquots for δ 13 C and δ 15 N determination, and a valuable tool for retrospectively correcting existing lipid‐extracted samples for which raw material may no longer exist.
Cabrol et al. (Fri,) studied this question.