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Dietary intake, drinking behavior, and physiology together influence the isotopic composition of herbivore tooth enamel, but the degree to which these factors influence the sequence of delta C-13 and delta O-18 values along the tooth crown remain underexplored. Analysis of serially sampled molars from sympatric wild and domesticated cap nines inhabiting the Gobi steppe-desert reveal inter-species distinction in carbon and oxygen isotope ratios as as well as pronounced differences in the amplitude of intra-tooth isotopic change. For domesticated sheep, consistently high delta C-13 values visible in intra-tooth sequences and C-13 enrichment in enamel with a winter season formation period indicates pronounced graze intake throughout the year including receipt of a C-4 fodder source during the winter months. This pattern contrasts with low delta C-13 values visible in the teeth of wild caprines indicating the intake of C-3 graze and browse throughout the year. Domesticated sheep also demonstrate a wide amplitude of intra-tooth oxygen isotope variation compared to wild caprines in addition to higher summer season maxima delta O-18 values and lower winter season minima delta O-18 values. The greater contribution of graze to the domesticated sheep diet suggests delta O-18-enriched leaf water strongly influences summer season delta O-18 values, while O-18-depleted groundwater imbibed from wells is likely responsible for low winter season delta O-18 values. The oxygen isotopic distinction between wild and domesticated sheep populations affirm previous observations that the ingestion of isotopically distinct water sources impacts body water oxygen isotopic composition and subsequent expression of delta(18)Ovalues in herbivore tooth carbonates. This has important implications for the use of delta O-18 values obtained from serially sampled teeth for reconstructing paleoenvironment, seasonality and also the movement of wild and domesticated herbivores through modem and ancient landscapes. (C) 2017 Elsevier B.V. All rights reserved.