KOROBOV, Natasha; DUMONT, Elizabeth; University of Massachusetts; University of Massachusetts: Modeling Bite Force Production: A Comparative Analysis within Chiroptera

It has been hypothesized that the morphology of the masticatory apparatus in mammals is constrained by the need to avoid dislocation of the temporomandibular joint (TMJ). This idea has formed the basis of several models of masticatory force production. Investigations of these models using morphological data from mammals with derived masticatory systems support this hypothesis. A key result of these studies is that bite force increases along the toothrow from anterior to posterior until a maximum force is reached. Beyond this point force remains constant. We expect the chewing/grinding teeth to be located in this region of maximum, constant bite force (Region 2). We examined whether the molars are contained within Region 2 in bats because bats exhibit a wide diversity of craniofacial form and relatively primitive masticatory morphology. Our data were collected from 5 families of bats representing a wide range of feeding behaviors, dental formulae and skull shapes. We calculated the length of Region 2 for each species and compared this length to measures of the lengths of the molar and premolar rows. As predicted, Region 2 always encompasses all of the molar teeth. However, the length of Region 2 varies among species, and is correlated with diet in several clades of bats. In the insectivorous bats, Region 2 was limited to the anterior border of the molar teeth. In plant-visiting bats the length of Region 2 also includes a significant portion of the premolars. Previous studies have documented diversity in premolar form among bats, and variation in species-specific food processing (biting) behaviors. The results of this study suggest that it may be advantageous for plant-visiting bats to exert large bite forces anterior to the molars, highlighting the role of the premolar teeth in food processing.