| Summary: | Results of field studies of beaked whales in the Gulf of California for December 2004-December 2006 are described. The goal is to determine the range of sound produced by beaked whales and to investigate beaked whale behavior and habitat. A minimum of 17 cetacean species (12 toothed and 5 baleen whales) were observed in 147 sightings. The proportion of sighted toothed whales and baleen whales was 67% and 32%, respectively. A comprehensive formulation for finite element modeling of biological tissues was developed. The mesh is voxel-based, and is generated automatically from CT scans. CT data from live, frozen, and thawed specimens of Tursiops truncatus showed similar results in tissues and organs for the following quantities: geometry, absolute density, and sound velocity. Simulated sound sources placed inside and outside of modeled adult male Cuvier's beaked whale (Ziphius cavirostris) revealed pathways for acoustic propagation into and out of the head. The simulations indicated a new gular pathway for sound reception. Propagated sound pressure waves enter the head from below and between the lower jaws, continuing toward the bony ear complexes through the internal mandibular fat bodies. N00244-06-C-0030.
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