Lipid-rich animal tissues have low δ¹³C values, which can lead to inaccurate ecological inferences. Chemical lipid extraction (LE) or correction models account for this depletion, but the need for LE or correction is tissue- and species-specific. Also, LE can alter δ¹⁵N values, increasing labor and costs because bulk samples must be analyzed for δ¹⁵N values separately. We studied the effects of LE on δ¹³C and δ¹⁵N values in liver, muscle, and skin of common bottlenose dolphins (Tursiops truncatus) and West Indian manatees (Trichechus manatus), two ecologically important species that occupy different trophic levels. We fit lipid-correction models to each species. We also performed a meta-analysis to more broadly determine the effects of LE across taxa, tissues, and trophic groups (carnivores, omnivores, and herbivores) and to fit lipid-correction models to different taxonomic and trophic groups. Lipid extraction increased the δ¹³C values in dolphin tissues but had little effect on manatee tissues and no effect on the δ¹⁵N values in either species. A mass-balance lipid-correction model best fit the data from all dolphin tissues, and a linear model best fit data for manatee liver while null models best fit data from manatee muscle and skin. Across 128 terrestrial and aquatic species, the effects of LE varied among tissues and were lower for herbivores compared to carnivores. The best-fitting lipid-correction models varied among tissue, taxa, and trophic groups. Finally, the δ¹⁵N values from muscle and liver were affected by lipid extraction. Our results strengthen the growing body of evidence that the need for LE is tissue- and species-specific, without a reliable C:N ratio predictive threshold. The prediction errors of lipid-correction models generally decreased with taxonomic- and trophic-specificity. The smaller effects of LE in herbivores may be due to differences in diet composition or the physiology of lipid synthesis in members of this trophic group. These results suggest researchers should use the most species-, tissue-, and trophic-group specific information on LE available and, if not available, perform LE on a subset of samples prior to analysis to determine effects.

This file contains three sheets. The first sheet, titled read.me, contains column title information for the second and third sheets. The second sheet contains data on stable carbon and nitrogen values of bulk and lipid-extracted samples from liver, skin, and muscle of common bottlenose dolphins (Tursiops truncatus) and West Indian manatees (Trichechus manatus). For this sheet, each row contains the sample and animal ID, tissue type, species, bulk and lipid extracted stable carbon and nitrogen values, and carbon:nitrogen (CN) ratios, as well as the difference between the bulk and lipid-extracted stable carbon and nitrogen values and CN ratios. The third sheet contains meta-analysis data that was obtained from the literature. For this sheet, each row represents a species and contains information on the taxonomic and trophic groups as well as data on the differences between bulk and lipid-extracted liver, muscle, and skin samples as well as bulk CN ratio for each tissue type and the reported instrumental error.