Built to bite: cranial design and function in the wrinkle-faced bat

One of the major goals of evolutionary biology is to explain phenotypic diversity and understand the limits imposed by those phenotypes. The cranial morphology of the wrinkle-faced bat Centurio senex (Family Phyllostomidae) is bizarre and enigmatic. Its extremely short and wide skull consistently emerges as an outlier in morphological studies and many researchers have speculated about its function. Here, we investigate the hypothesis that the unique skull morphology of Centurio is associated with the ability to generate high bite forces and/or high bite forces at wide gapes. We accomplish this by comparing bite force data gathered in the field and estimates of gape limitations gathered from museum specimens. We also examine the possibility that Centurio uses unique feeding behaviors that may impose unique loading regimes on the facial skeleton. We found that relative to head size, Centurio generates the strongest bites known for any fruit-eating phyllostomid bat, but that its ability to generate high bite forces at wide gape angles is likely limited. We also propose that its exceptionally strong bite indicates the ability to consume hard food items when other resources are limited, and that these 'resource bottlenecks' may have imposed strong selective pressure on its skull morphology. Behavioral data indicate that Centurio exhibits a unique reliance on unilateral biting (loading) during feeding. Based on data summarizing bite force, estimates of gape ability and feeding behavior, we suggest that Centurio's exceptionally short and wide skull reflects adaptations for high bite forces and repeated unilateral loading of the facial skeleton during feeding.