Shark teeth zinc isotope values document intrapopulation foraging differences related to ontogeny and sex.

Trophic ecology and resource use are challenging to discern in migratory marine species, including sharks. However, effective management and conservation strategies depend on understanding these life history details. Here we investigate whether dental enameloid zinc isotope (δZn) values can be used to infer intrapopulation differences in foraging ecology by comparing δZn with same-tooth collagen carbon and nitrogen (δC, δN) values from critically endangered sand tiger sharks (Carcharias taurus) from Delaware Bay (USA). We document ontogeny and sex-related isotopic differences indicating distinct diet and habitat use at the time of tooth formation. Adult females have the most distinct isotopic niche, likely feeding on higher trophic level prey in a distinct habitat. This multi-proxy approach characterises an animal's isotopic niche in greater detail than traditional isotope analysis alone and shows that δZn analysis can highlight intrapopulation dietary variability thereby informing conservation management and, due to good δZn fossil tooth preservation, palaeoecological reconstructions.