Parts of a whole: isotopic offset between single keratin-based tissues
and whole-body values of birds and mammals
Abstract
Abstract RATIONALE Stable isotope analysis is a frequently used
tool in ecology for unraveling dietary dynamics and trophic
relationships. In isotopic studies that use mixing models to infer diet,
a single tissue is often used to represent the isotopic values of a
whole organism. Here, we examine that assumption in keratin-based
tissues and provide recommendations for isotopic diet studies of animals
that consume prey whole. METHODS By comparing carbon ( δ
13C) and nitrogen ( δ 15N)
stable isotope values in single tissues of mammals and birds, this study
aims to elucidate the extent to which nondestructive sampling methods in
tissues such as hair and feathers, accurately represent the overall
isotopic composition of four mammalian species (rats, mice, rabbits,
guinea pigs) and one avian species (quail). RESULTS We found that
keratin-based tissue and the homogenized whole-body samples were
significantly different in δ 13C values in
mammals (mean 𝚫 13C -1.93 ± 0.37‰) but not in birds.
Feathers differed significantly from whole body in δ
15N values in birds (mean 𝚫 15N
-0.32 ± 0.11‰), but δ 15N values did not differ
among hair and the whole body of mammals. CONCLUSIONS We provide a
mathematical correction for diet reconstruction based on specific
tissues, especially for animals consuming whole prey. We suggest that
future studies reconsider the assumption that non-invasively sampled
tissues are representative of whole-body isotopic values.