Dietary paleoecology of bison and horses on the mammoth steppe of eastern Beringia based on dental microwear and mesowear analyses

Abstract

Abstract In contrast to the modern Arctic, high-latitude ecosystems of the Late Pleistocene supported a diverse range of large mammalian herbivores, including abundant bison (Bison priscus) and horses (Equus sp.). This ‘mammoth steppe’ biome has no extant analog and modern tundra vegetation is likely incapable of supporting such a high density of large mammals. Compared to modern Arctic ecosystems, higher diversity and biomass of Late Pleistocene large mammal populations may have been sustained by more nutritious forage and/or dietary niche partitioning. We used dental microwear texture analysis and dental mesowear analysis of bison and horses (Bison priscus, Equus sp.) to characterize diet and assess the degree to which dietary differences supported co-existence of these dominant and likely competing herbivores on the mammoth steppe. Additionally, we compared microwear and mesowear of Late Pleistocene specimens to modern Alaska bison (reintroduced Bison bison athabascae and introduced Bison bison bison) and published microwear and mesowear data for extant bovids and equids. Our results demonstrate that Late Pleistocene bison and horses had less abrasive diets than modern obligate grazers, suggesting that these “grazers” of the mammoth steppe likely incorporated more forbs in their diets than modern grazers. Furthermore, Late Pleistocene bison and horses ate foods with similar textures, indicating that dietary niche partitioning alone cannot explain their co-occurrence. However, taphonomic differences between bison and horse specimens indicate potential spatial or temporal niche partitioning during the Late Pleistocene.