UNGULATES AS MAJOR TAPHONOMIC AGENTS AND BONE RECYCLERS IN AN ARCTIC ECOSYSTEM

Ungulates are rarely the focus of bone gnawing studies, though they consume bone in response to seasonally driven nutrient stress and are often more abundant than co-occurring carnivoran bone modifiers. As a result, the taphonomic impacts of ungulates on bone assemblages may be high, but remain underappreciated. Here, we assess whether established criteria adequately identify the range of ungulate bone consumption or require further development. We then evaluate the exploitation of bones by co-occurring ungulates, carnivores, and rodents as an indication of resource competition. We collected bones accumulating on modern caribou calving grounds of the Arctic National Wildlife Refuge (Alaska), where adult female caribou undergo elevated nutrient stresses due to lactation and antler regrowth. Standardized surveys yielded over 1,000 antlers and several hundred postcranial bones. Each bone element was visually inspected for modifications, which were then compared to established criteria for recognizing damage caused by ungulates (Dama, Rangifer), carnivores (Ursus, Canis, Vulpes) and rodents (Urocitellus, Microtus). We identified 22 distinct modification classes with characteristic pits, punctures, furrows, and fractures. We attributed these classes to caribou (n=12 classes), carnivores (n=1), rodents (n=1), and to non-gnawing damage (n=8). Nine of the twelve caribou classes include previously undocumented patterns of ungulate bone modification, including triangular punctures; which are consistent with the cusp shape of ungulate cheek teeth and inconsistent with teeth of other modifiers. Triangular punctures are visually distinct and useful for identifying bones with lower-intensity caribou modification which would otherwise go unrecognized. We found that ungulates and carnivores target different bone elements. Caribou gnawing was recognized on ~88% of all shed antlers, but <10% of postcrania. Carnivore modifications were readily observed on postcrania (>30%), but were not present on shed antlers. Rodent gnawing was limited, but present on both antlers (<3%) and postcrania (<5%). Caribou are the dominant bone recycler on their calving grounds, but specialization by co-occurring taxa on subsets of available skeletal elements likely reduces inter-taxon competition over bone resources.