Meeting Abstract
Maximum bite force is an important metric of feeding performance that defines the dietary ecology of many vertebrates. In mammals, theoretical analyses and empirical studies of muscle function, gape angle and bite force suggest a trade-off between maximum bite force and gape; cranial morphologies that enable high mechanical advantage have decreased ability to generate high bite forces at wide gapes, and vice versa. Nevertheless, very few studies have confirmed these relationships in free-ranging mammals biting voluntarily, and fewer have contrasted these measurements with those derived from biomechanical models to examine the morphological features underlying the gape-bite force relationship across species. I document the variation in bite force with respect to gape angle in a diverse sample of free-ranging bat species, and compare these results with predictions from 3D lever models of the feeding apparatus that simulate biting at increasing gapes. In vivo and model data corroborated that bite force decreases significantly as gape angle increases across species, but there is substantial intraspecific variation in the data obtained from live bats. Bite force predictions from biomechanical models revealed that species with high mechanical advantage experience a steeper drop in bite force with increasing gape, despite a smaller loss in force due to negative moments about the temporomandibular joint. These bat species correspond to short-faced frugivores and insectivores that specialize on mechanically challenging prey. Interspecific differences also highlight the influence of jaw adductor stretch factors in these relationships. Altogether, these results suggest that gape-mediated changes in bite force can be explained both by behavioral effects and cranial morphology, and that these links are relevant for functional analyses of mammal dietary ecology.
