Frequencies of Spiral and Green-Bone Fractures on Ungulate Limb Bones in Modern Surface Assemblages

During observational fieldwork in undisturbed ranges of free-roaming bison and moose, I have identified approximately 8% of surface bones as spirally or green-fractured due to documented carnivore activity, and 5% as spirally or green-fractured due to trampling or dust wallowing by bison. The bones of smaller species suffer up to 50% breakage. Bone modifications by wild wolves and bears are briefly described, as are characteristics of fractures caused by trampling and wallowing.