Seasonality of calving and characteristics of the parturition process in domestic reindeer in the republic of Sakha (Yakutia)

Reindeer herding remains a cornerstone of traditional livelihood for indigenous peoples of the Republic of Sakha (Yakutia), where harsh climatic conditions profoundly shape the reproductive cycle of domestic reindeer (Rangifer tarandus). This study examines the seasonality of calving and the morphofunctional characteristics of the parturition process in female reindeer (vaizhenki) across diverse natural and climatic zones of the republic. Data were collected from reindeer herding farms in Olenyoksky, Momsky, Bulunsky, Nizhnekolymsky, and Anabarsky uluses during peak calving periods (April–June). The earliest calving was observed in Nizhnekolymsky ulus, whereas in Anabarsky, Bulunsky, and the northern part of Olenyoksky ulus, mass calving typically begins in early May and concludes in the third decade of May to the first decade of June. The overall calving season lasts 30–45 days (6–9 five -day periods), with 70–80% of females calving within a highly synchronized window of only 3–4 five-day periods. This pronounced reproductive synchrony reflects adaptation to the short favorable season and is influenced by local climatic factors, rut timing, and the physiological condition of breeding females. Early and compact calving holds significant practical value for herds undertaking long nomadic migrations, as early-born calves gain sufficient strength by river breakup and the onset of mass insect emergence, thereby reducing risks of hypothermia, pneumonia, and mortality.
These findings highlight adaptive mechanisms in the reproductive system of reindeer to Arctic environments and offer valuable insights for improving herding technologies, veterinary monitoring, and selective breeding practices in Yakutian reindeer farms.

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