Meeting Abstract

25.2  Jan. 5  Finite element modeling of head butting in the goat (Capra hircus) FARKE, A.A.; Stony Brook University, New York afarke@ic.sunysb.edu

Although cranial sinuses are often perceived to be functionless spaces within the skull, the locations and sizes of these sinuses may have important functional consequences. For example, large sinuses may reduce overall skull mass, weaken the skull, and change the path by which forces are transmitted through the skull. It has been proposed that the frontal sinuses of sheep and goats, animals that engage in sometimes quite forceful head butting, protect the brain by acting as �shock absorbers.� Under this scenario, it is predicted that the sinuses reduce the strain and strain energy density inside the braincase, among other effects. In order to test this hypothesis, two 3D models of the skull of the domesticated goat (Capra hircus) were created from CT scans. One model had a completely solid frontal, and the other had a space in the frontal representing the frontal sinus. Using finite element analysis, the models were loaded statically on the anterior surface of the horns, to simulate the forces of head butting. In general, the model with sinuses had higher magnitudes of strain than the model without sinuses. This is not surprising, given that the former has less bone to absorb and distribute forces than the latter. Additionally, the model with sinuses had higher magnitudes of both strain and strain energy density on the endocranial surface of the braincase; this counters the proposals that the sinuses function as shock absorbers. Alternative functions currently are being explored. Perhaps the �inflated� frontal bone of sheep and goats (contrasting with the relatively thin frontals in many other horned animals) protects the brain by separating it spatially from the horncores without causing a detrimental increase of strain in the walls of the endocranium.