Skull Morphology, Bite Force, and Diet in Insectivorous Bats from Tropical Dry Forests in Colombia

SIMPLE SUMMARY: The cranial structure is highly variable among mammals and thought to reflect specializations for feeding and echolocation in bats. However, recent analyses of skull structure, feeding behavior and bite force across a wide range of bats suggest that correlations between morphology, performance, and ecology are not as delineated as previously thought. For example, most of the variations in bite force in insectivorous bats have been explained by differences in body size rather than specific cranial traits. We tested several relationships associated with the cranium to ascertain predictors of bite force in different bat species based on in vivo measurements from the Colombian tropical dry forests and museum specimens. Our data show that skull size had a significant contribution to bite force for beetle-eating bats, such as Noctilio albiventris, Molossus molossus, M. coibensis, and Molossops temminckii. Cranial traits and the combined action of the jaw morphology generate a biomechanical comparative advantage that allows these species to feed on “hard” prey, supporting the hypothesis that skull morphology, bite force, and diet are linked in insectivorous bats. ABSTRACT: In Neotropical bats, studies on bite force have focused mainly on differences in trophic ecology, and little is known about whether factors other than body size generate interspecific differences in bite force amongst insectivorous bats and, consequently, in their diets. We tested if bite force is related to skull morphology and also to diet in an assemblage of Neotropical insectivorous bats from tropical dry forests in the inter-Andean central valley in Colombia. It is predicted that the preference of prey types among insectivorous species is based on bite force and cranial characteristics. We also evaluated whether skull morphology varies depending on the species and sex. Cranial measurements and correlations between morphological variation and bite force were examined for 10 insectivorous bat species. We calculated the size-independent mechanical advantage for the mandibular (jaw) lever system. In all species, bite force increased with length of the skull and the jaw more than other cranial measurements. Obligate insectivorous species were morphologically different from the omnivorous Noctilio albiventris, which feeds primarily on insects, but also consumes fish and fruits. Our results show that bite force and skull morphology are closely linked to diets in Neotropical insectivorous bats and, consequently, these traits are key to the interactions within the assemblage and with their prey.