Meeting Abstract

P3.131  Wednesday, Jan. 6  Quantitative Computed Tomography of Rorqual Mandibles: Mechanical Implications for Lunge-feeding FIELD, D.J.*; GOLDBOGEN, J.A.; CAMPBELL-MALONE, R.; BEN-ZVI, M.; PINTO, S.J.; SHADWICK, R.E.; Univ. of British Columbia; Univ. of British Columbia; Brown University; Univ. of British Columbia; Univ. of British Columbia; Univ. of British Columbia danieljaredfield@gmail.com

Rorqual whales lunge at high speed with mouth open to nearly 90 degrees in order to engulf large volumes of prey-laden water. This feeding process is enabled by extremely large skulls and mandibles that effectively increase mouth area, thereby enhancing the flux of water into the mouth. When these mandibles are lowered during a lunge, they are exposed to high drag and therefore may be subject to significant amounts of bending. Quantitative computed tomography (QCT) was used to investigate the morphology of a pair of sub-adult humpback whale mandibles (length = 2.10 m). QCT data indicated a significant increase in mineral density and cross-sectional area from the mandibular symphysis to the coronoid process, thereby providing high resistance to bending much like a cantilever beam. These data contrast significantly with the density distribution previously reported for right whales, which employ a different filter feeding method that does not involve high speed or extreme gape angles. This comparison suggests that adaptive bone remodeling is a significant contributing factor in establishing mandibular bone density distributions in cetaceans. We conclude that the morphological design of rorqual mandibles functions to accommodate high drag loads during lunge-feeding without experiencing high strain. To further test this hypothesis, we incorporated QCT data into a finite element model and explored the mechanical behavior of the bone when simulated drag forces were applied.