The Southernmost European Record of the Steppe Polecat (Mustela eversmanni) from the Late Pleistocene: Chaya Cave, Bulgaria

The steppe polecat (Mustela eversmanni Lesson, 1827) is a characteristic element of Eurasian steppe ecosystems whose distribution is closely linked to the expansion of open landscapes. Although the species was widespread in Europe during the Late Pleistocene, its fossil record in Southeastern Europe remains poorly documented. Here we report the first confirmed Pleistocene occurrence of M. eversmanni in Bulgaria, based on fossil material recovered from Late Pleistocene deposits of Chaya Cave in the Western Rhodope Mountains. The studied assemblage includes two crania and three hemimandibles identified through comparative morphological and morphometric analyses. The fossils display diagnostic characters of M. eversmanni, including a strongly developed postorbital constriction, robust mandibular morphology, and dental features associated with predation in open environments. Comparative analyses confirm their attribution to the species and place them within the variability of known Late Pleistocene populations. The Chaya Cave specimens represent the southernmost known occurrence of the steppe polecat in Europe, extending the previously documented range of the species during the Late Pleistocene. Their presence indicates the expansion of steppe-associated habitats into the central Balkan Peninsula during cold and relatively dry climatic phases. The occurrence of M. eversmanni at approximately 1300 m above sea level further suggests the development of open landscapes in mountainous environments under glacial conditions. These findings provide new insights into the paleoecology and biogeography of Southeastern Europe and highlight the importance of Chaya Cave as a valuable geoheritage site preserving evidence of environmental and landscape change during the Late Pleistocene.