Nitrogen- and carbon-isotope fractionation between mothers and offspring in red-backed voles (Clethrionomys gapperi)

Abstract

Small mammals are income breeders, but the degree to which females draw from maternal reserves and partition nutrients to the mammary glands in the wild is not known. This study examined stable-nitrogen and stable-carbon isotopes in red-backed vole, Clethrionomys gapperi (Vigors, 1830), hair to determine mother–offspring trophic relationships and to consider the extent to which voles rely on maternal reserves during lactation. Both dependent and independent young showed isotopic enrichment in 15N and depletion of 13C in their hair relative to mothers. We suggest that growing offspring, both dependent and independent, may catabolize body reserves to support both growth and moult. We propose that the nitrogen- and carbon-isotope compositions of hair may be more useful indicators of metabolic rate than mother–offspring trophic relationships in small mammals.