Biting Style and the Biomechanics of Feeding in Mammals Elizabeth R. Dumont (PI), Ian R. Grosse (Co-PI) University of Massachusetts, Amherst
The evolutionary history of mammals is largely a story about exploiting an ever broader array of food resources. While the first mammals were insect-eaters, modern mammals specialize in diets ranging from insects to fruits, foliage, meat, and plankton. This diversity in diet is reflected in the shape of the skull - the primary 'tool' that mammals use to bite and chew food. Importantly, however, the underlying mechanism driving the evolution of this diversity is unknown. This study explores the importance of the biomechanical link between the forces generated during biting and the anatomy of mammal skulls that safely and optimally bear and disperse these forces. Further, this study investigates the role of this relationship in the evolution of diversity in skull shape. Previous analyses of mammalian feeding have taken one of two approaches, each of which has inherent limitations. Broad comparative studies document correlations between skull shape and diet, but fall short of testing the causal mechanisms underlying the correlations. On the other hand, detailed experimental studies document how bones and muscles behave during feeding, but the experimental conditions are often far from natural. This study will be the first to combine data on biting behavior and bite force gathered in the field with biomechanical experiments carried out in the laboratory. The first aim is to investigate how different biting styles apply loads to the skull and how those loads are dispersed. Causal links between routine biting behaviors and morphology will be identified by comparing the loading regimes imposed by different biting styles within species. The second aim is to address two other unresolved issues regarding feeding in mammals: the extent to which skull shape is limited by other sensory systems (in this case, vision), and the strength of the facial skeleton relative to forces generated during feeding. Answers to these issues may explain why some lineages of mammals exhibit a wider variety of skull shapes than do others. Initially, the forces generated by biting will be measured and the feeding behavior of mammals will be documented in the field. Next, the mechanical implications of these behaviors will be investigated in the laboratory using finite element (FE) modeling and analysis, a physics-based numerical technique widely used by engineers to assess the mechanical behavior of physical systems. FE analysis (FEA) provides a truly novel perspective on form-function relationships, but is not yet accessible to most biologists. An objective is to make FEA more accessible by accomplishing two specific methodological aims: 1) determine the extent to which FE models of mammal skulls can be simplified and still yield sufficiently accurate results, and 2) develop protocols for efficiently translating CT-scans into three dimensional FE models. These results will be communicated to the biology community through peer-reviewed scientific publications, presentations, and workshops. This collaboration between a functional anatomist and a mechanical engineer offers an excellent opportunity to train graduate students and to expose undergraduates to collaborative, interdisciplinary research in biomechanics, comparative anatomy, and mechanical engineering. Graduate Research Assistants will conduct their own original research, and help the PIs to mentor 4-6 undergraduate research projects. These projects will serve as a springboard to graduate studies in biology and/or engineering.
