Relative Effectiveness of Different Osteological Predictors of Bite Force in Carnivora

Abstract

Bite force--a parameter of ecological importance among mammals because it correlates with the mechanical limitations of the feeding apparatus–is frequently estimated using anatomical correlates including estimates of jaw adductor muscle size (e.g., physiological cross-sectional area) and their attachment areas. However, validation of the use of osteological estimates of jaw adductor size and bite force across ecomorphologically diverse mammalian samples has been limited. Moreover, in recent years, the ability to quickly and easily extract increasingly complex measurements (e.g., 3D surface scans) has increased. Nonetheless, working with 3D scanning is typically more expensive and time consuming than is obtaining and processing 2D images, and thus it is important to question whether it is also more effective. In this study, we use a sample of 40 carnivoran species spanning nearly four orders of magnitude in body size (~60 g in Mustela nivalis to ~500 g in Ursus arctos) and dietary diversity ranging from frugivory to insectivory, generalized omnivory, and hypercarnivory, to compare the efficacy of several osteological measurements in predicting jaw adductor muscle size. We find that Thomason ‘dry skull’ technique provides a stronger correlation with muscle mass than estimates derived directly from two- or three-dimensionally measured muscle attachment areas, suggesting that estimates that account for muscle thickness are more effective in predicting muscle mass than those that only reflect the muscle's attachment areas. However, of muscle attachment measurements, areas that are taken from 3D surface scans or µCT data provide stronger estimates of muscle size than do surfaces measured from 2D lateral photographs.