Meeting Abstract

90.2  Wednesday, Jan. 7  Quantifying the Influence of Allometry on Mechanical Performance: A Study of the Evolution of Felid Cranial Form SLATER, G.J.; Univ. of California, Los Angeles gslater@ucla.edu

Skull form within a lineage often varies allometrically, but the impacts of this shape variation on performance are rarely quantified. The skulls of large and small felids are shaped very differently. Big cats have relatively elongate facial skeletons and reduced neurocrania relative to small cats. Given their elongate rostra, large cat skulls are expected to exhibit increased bending moments and reduce strength in torsion. Here, I use Finite Element Analysis (FEA) of three cat skulls, spanning the full range of body sizes and skull shapes, to test the mechanical implications of skull shape allometry. FE models were analyzed using a newly developed scaling method that allows more accurate determination of the impacts of shape on performance. Large cats produced relatively lower bite forces than small cats, but these differences were small and empirical bite force estimates generally follow expectations of geometric similarity. Nevertheless, despite their longer rostra, large cats had stronger and more mechanically efficient skulls than small cats during both bilateral and unilateral canine biting. Large cats achieve this efficiency, in part, by increasing skull bone volume relative to surface area, i.e. they have thicker skulls. Thus, allometry of external skull form in big cats appears to be driven more by the need to increase gape to kill larger prey, rather than a need to produce and resist greater absolute bite forces and the unpredictable loads from large struggling prey. To compensate for the latter, big cats evolve thicker skulls despite possible trade-offs in increased mass and metabolic costs.