Meeting Abstract

80.2  Friday, Jan. 7  Mechanics, hydrodynamics and energetics of blue whale lunge feeding: predatory strategies and efficiency dependence on krill density GOLDBOGEN, Jeremy, A.*; CALAMBOKIDIS, John; MCKENNA, Megan; OLESON, Erin; POTVIN, Jean; PYENSON, Nick; SCHORR, Greg; SHADWICK, Robert; University of California, San Diego; Cascadia Research Collective; University of California, San Diego; NOAA; Saint Louis University; Smithsonian NMNH; Cascadia Research Collective; University of British Columbia jergold@ucsd.edu

We attached high-resolution digital tags to foraging blue whales to investigate the mechanics of lunge feeding at depth. These kinematic data were incorporated into unsteady hydrodynamic models to estimate the amount of drag sustained during lunge feeding. Our analysis suggests that, despite the large amount of mechanical work required to overcome drag during lunge feeding, a large amount of prey and therefore energy is obtained during engulfment. These data indicate that foraging efficiency for blue whales is significantly higher than other marine mammals by nearly an order of magnitude, but only if lunges target extremely high densities of krill. Our analysis helps explain larger scale foraging patterns in rorqual whales, where lunge feeding behavior tracks the diel migration of krill patches from the sea surface to over 300 m deep. At a finer scale, the majority of lunges were executed from below krill patches at significantly higher body angles compared to other rorqual whales. Although maneuverability is hindered by their extreme body size, blue whales will avoid visual detection when attacking from below. This type of ambush strategy delays the escape response and the rapid expansion of krill patches during a lunge, thereby increasing the proportion of krill captured and further enhancing the efficiency of lunge feeding.