Diet and morphological variation in bison (Bison bison) from the Bighorn Basin, Wyoming, USA

Cranial morphology has been used to examine ecological pressures on bison ( Bison bison ) populations and to place isolated crania within chronological and evolutionary contexts. This study analyzes 114 historic and 10 modern, ranched bison from the Bighorn Basin (Wyoming, USA) to assess morphological, dietary, and ecological changes before and after the 19th-century population bottleneck. Up to 26 morphological measurements were recorded on each specimen. Late Holocene bison from the region are morphologically consistent with contemporaneous populations elsewhere in North America. In contrast, modern ranched bison exhibit more curved horn cores, potentially reflecting management-related changes in herd dynamics. Stable isotope analyses (δ 13 C and δ 15 N) indicate that late Holocene Bighorn Basin bison consumed diets comparable to those of modern herds, both free-ranging, such as Yellowstone National Park, and ranched. Results offer insight into past variation in bison dietary ecology with the potential to inform modern conservation strategies for bison management.