Meeting Abstract
Large body size is widely recognized to confer many benefits, including reduced transport costs and enhanced diving capacity. Such advantages should allow divers to increase their ability to forage at depth, increasing overall foraging efficiency. Rorqual whales engulf a large mass of prey-laden water at high speed and filter it through baleen plates retaining prey. This lunge feeding mechanism incurs a large energetic cost due to high drag, but provides the animal with extraordinary prey consumption rates. However, as engulfment capacity increases with body length across species (Engulfment=length3.2*100.61,r2=0.96), the surface area of the baleen filter does not increase proportionally (Baleen area=length1.85*100.18,r2=0.83).Therefore, we hypothesize that these scaling differences lead to longer filtration time (Filter time α length1.5) for rorquals of larger body size because the baleen surface area filters a disproportionally large amount of water. We tested this hypothesis on 4 rorqual species using 40 cetacean-mounted video and 3D accelerometry tag deployments with corresponding drone photogrammetry that provided direct measures of body size, lunge rates, and filtration times. Our findings show that filter time increased with body length (Filter time=length1.8*10-0.6, r2= 0.86), whereas the number of lunges per dive decreased with size (Lunges per dive =length-0.8*101.7, r2=0.55). Although larger rorqual whales should have increased diving capacity, the disproportional cost and filter time required to engulf larger volumes progressively limits dive time that could otherwise be spent selecting the highest quality prey patches.
