ABSTRACT The faunal remains from the late Neolithic site of Ness of Brodgar on the Orkney Islands (UK) provide a unique opportunity to investigate past adaptations of animal husbandry strategies to the Northern island environment, as well as the potential management of red deer. In this study, sheep and red deer mandibles and loose teeth (dP4 & M3) from the Ness of Brodgar were studied to construct age-at-death profiles, and analysed for δ13C, δ15N and δ18O. The mortality profile showed that around half of the analysed sheep were slaughtered when they reached maturity (i.e. after 2–4 years of life), consistent with a husbandry regime targeted at meat production. The stable isotope evidence indicates seaweed consumption in winter by several sheep (domesticates), but not by red deer (wild, possibly managed fauna). This dietary difference may have resulted from anthropogenically mediated influences, e.g. restriction of red deer habitats to upland areas. The varying extent of seaweed consumption between individual sheep and between Neolithic Orkney sites suggests differences in sheep husbandry practices across Orkney, indicating that the adaptation to consume seaweed was not ubiquitous on Orkney in the Neolithic, and did not follow a linear development.