Meeting Abstract

49.1  Tuesday, Jan. 5  Big heads, big gulps and high drag: mechanics and energetics of rorqual lunge feeding GOLDBOGEN, J. A.*; CALAMBOKIDIS, J. ; OLESON, E. M.; POTVIN, J.; SCHORR, G.; SHADWICK, R. E.; Univ. of British Columbia; Cascadia Research Collective; Univ. of California, San Diego; Saint Louis University; Cascadia Research Collective; Univ. of British Columbia jgoldbogen@gmail.com

Rorqual whales are not only some of the largest animals to have ever lived, but they also exhibit one of the most unique feeding methods among aquatic vertebrates. To investigate the mechanics and energetics of rorqual lunge feeding, we deployed high-resolution acoustic tags to three rorqual species that differ in average body size (blue, fin and humpback whales). We determined instantaneous body speed during lunges from the level of flow noise measured by the hydrophone within the tag. These kinematic data were then integrated with morphological data into an unsteady hydrodynamic model to estimate engulfment volume, drag, and work. Maximum lunge speed, engulfment volume and filter time increased with body size, but relative to body size there was no significant difference. In contrast, both the absolute and mass-specific work against drag increased with body size, which suggests a relatively higher cost of a lunge for larger rorquals. This hypothesis is corroborated by dive profile data which show a decrease in the number of lunges that are performed per dive and a relatively higher increase in post-dive recovery time following lunges at depth. Given these scaling patterns, I discuss the ecological and evolutionary implications of lunge feeding, including the energetic requirements of, and physical limits to, big body size in rorquals.