Meeting Abstract

P2.80  Wednesday, Jan. 5  Computer simulations of engulfment drag by small and large lunge-feeding rorquals POTVIN, Jean*; GOLDBOGEN, Jeremy A; SHADWICK, Robert E; Saint Louis University; Univ. of California, San Diego; Univ. of British Columbia potvinj@slu.edu

Lunge feeding by rorqual whales represents one of the most extreme feeding methods among aquatic vertebrates. The strategy requires the momentary abandonment of the body-streamlining that make their non-feeding locomotion so energy-efficient, in favor of a high-drag mouth-open configuration aimed at engulfing the maximum amount of prey-laden water. Although the basic mechanics of this process is well-understood, the body size-scaling of the associated drag costs is not. We present the latest simulations of a scaling study of the costs specifically incurred during engulfment using the Basic Lunge Feeding model (Potvin et al. 2009 J. Roy. Soc. Interface), a numerical scheme that treats a lunging whale and engulfed mass as two separate bodies interacting via the active push on the latter by buccal cavity wall musculature (Shadwick et al. 2011, this conference). Here the model has been upgraded to incorporate a direct coupling between gape rate and (whale) speed (Potvin et al. 2010 Journal of Theoretical Biology) as well as an explicit simulation of water capture in the cavity anterior to the temporomandibular joint (TMJ). The upgrade uses also the new hypothesis of Synchronized Engulfment in which the metering of the cavity’s push results in the complete filling of the cavity posterior to the TMJ by the moment of maximum gape, followed by that of the cavity anterior to the TMJ by mouth closure. Our analysis suggests engulfment duration to increase with body length by as much as 100% over the entire size range in fin whales (Balaenoptera physalus). It shows also that the energy losses due to drag (mass specific) are to increase between 40% and 200% depending on the predator-prey interactions influencing a whale’s pre-engulfment speeds.