Winter is coming: seasonality of ancient pastoral nomadic practices revealed in the carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic record of Xiongnu caprines

Winter is a challenging time for herders, who must carefully consider both calculable and unpredictable environmental circumstances in order to ensure that their livestock survive the season and retain body condition adequate for the production of offspring and animal products during the rest of the year. Today, pastoral nomads of Inner Asia employ several strategies that serve to alleviate graze shortages associated with the onset of the winter season, including winter pasturing and foddering. However, the emergence of such management strategies in ancient pastoral nomadic communities remains poorly understood. Ancient livestock husbandry practices related to seasonal dietary augmentation are documented here for the first time in an Inner Asian context. Carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic analyses of incrementally sampled second mandibular molar dentin collagens from caprines recovered from Iron Age Xiongnu (300 bc to 200 ad) contexts in the Gobi Desert, Mongolia, reveal patterned intra-tooth isotopic variation, indicating winter provisioning of animals with a fodder source that included C₄ plants and pasturing of livestock on winter pastures enriched in ¹⁵N by manure. Inter-individual variation in the shape of carbon and nitrogen isotopic curves suggests differences in the timing and intensity of application of fodder provisioning and winter pasturing by Xiongnu pastoralists to different animals. These isotopic data reveal that herding practices focused on promoting livestock survivorship through the harsh winter months were in use by Xiongnu pastoral nomads over 2000 years ago.