Testing the use of southern France and Cyprus mouflons as a reference to reconstruct birth season in sheep from oxygen isotope analysis in teeth

Reconstructing past sheep birth seasons relies on oxygen isotope analysis in dental enamel, using modern reference datasets with known birth seasons for comparison. However, the comparability of dental growth calendar between modern and ancient sheep remains uncertain. The current mouflons in Europe, descended from Neolithic domestic sheep that later became feral in Corsica, Sardinia, and Cyprus, are amongst the closest living relatives of Neolithic sheep. Their suitability as references for the estimation of the birth season was explored by analysing the third molar of individuals from two populations giving birth in the spring: Cyprus mouflons (n = 7) and Mediterranean mouflons from southern France (n = 10). Results from oxygen isotope analysis of dental enamel reflect environmental and management differences (e.g., wild vs. captive conditions, local climate and seasonal temperature fluctuations). Isotopic sequence modelling indicated a good agreement between the Mediterranean mouflons from southern France and previously published western European sheep references. However, a radical shift in the record of the δ¹⁸O values of the seasonal cycle between the Cyprus mouflon and the sheep references has been observed.

This divergence suggests distinct dental growth calendars between the Cyprus mouflons and the remaining Ovis included in the study, which may be attributed to a different genetic lineage, reduced genetic diversity in Cyprus mouflons due to one or more founder events—potentially leading to the expression of traits not present or rarely present in the source population—and/or long-term isolation resulting in phylogenetic drift.

These findings suggest that Mediterranean mouflons from southern France are as suitable as modern sheep breeds as references for reconstructing past birth seasons in Western Europe. In contrast, the use of the Cyprus mouflons as a reference requires further investigation, both in the context of Cyprus and more broadly across the Near East.