Stable nitrogen and carbon isotope discrimination between juveniles and adults in an income-breeding small mammal (Peromyscus maniculatus)

We investigated the stable nitrogen- and carbon-isotope compositions of blood, liver, muscle and hair of income breeding deer mice (Peromyscus maniculatus) to determine the extent to which stable isotope compositions of mothers and offspring differed. We found small differences between the δ¹⁵N and δ¹³C values of dependent offspring and adult tissues (by a magnitude of −0.8‰ to 1.1‰ for ¹⁵N and 0.3–0.9‰ for ¹³C), and limited ¹⁵N discrimination between juvenile tissues and milk, which explains the small mother-offspring trophic effects in isotopic composition. Discrimination of ¹⁵N between offspring and adults was greater than expected but smaller than known for capital breeding mammals, suggesting that different biochemical pathways for milk production and processing may affect the discrimination of ¹⁵N in these systems.