Sheep and goat birth seasonality at Early Byzantine Sagalassos

The seasonality of birth, a key parameter when addressing past domestic livestock management, can be investigated through serial stable oxygen isotope analysis in tooth enamel. The assessment of the season of births requires furthermore the availability of modern reference data set, existing for cattle, sheep, pigs or llamas. The ancient site of Sagalassos, in the Taurus Mountains (SW Turkey), has delivered a large assemblage of sheep and goat remains. The osteological analysis revealed a predominance of goat over sheep, with a ratio varying between 65 and 90% over time. Goats and sheep were kept at an old age for the production of milk, wool/hair, as well as for horn-working and hide exploitation. A stable oxygen isotope (δ18O) analysis focussing on mandibular M2s was undertaken to investigate goat and sheep livestock demographic management during the Early Byzantine period (450-680 CE). ZooMS was used to confirm specific attribution of selected specimens (ten goats, eight sheep). Ten modern hair goats collected in the late 1990s in the context of a research project on small ruminant herd management in the Eastern Mediterranean were also sampled to provide a modern comparative for the assessment of birth season. The modern goat δ18O sequences were modelled according to Balasse et al. (2012) and compared with the existing sheep reference data set. The comparison suggests a different timing in the isotope record between sheep and goats and argues for the use of species-specific comparative for the assessment of birth season in archaeological herds. The comparison of the modern and archaeological goat δ18O sequences indicate a quite restricted season of births in spring for the latter. On the contrary, sheep births were spread out over roughly six months, from late winter/early spring to early-/mid-summer. More modern goat comparatives are needed to enrich this dataset. Keywords: Stable oxygen isotope, tooth enamel, birth seasonality, goat, Sagalassos.

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