Intermittent engulfment filtration feeding, a foraging modality unique to rorqual whales, is an energetically efficient strategy that relies on abundant and dense prey aggregations and which enabled the evolution of the largest animals. The efficiency of this strategy increases with body size, yet the smallest rorqual whales (minke whales) still appear to forage at several times the efficiency of many other cetacean species. Additionally, baleen whale ancestors exhibited much lower body sizes overall, so the absence of rorqual whales smaller than extant minkes is conspicuous and largely unexplained. Similarly, the linearly increasing efficiency of rorqual whale foraging with body size does not suggest an upper limit to size, leaving unexplained why no animals larger than a blue whale have ever been discovered. Our best answers to date for these related problems involve the intersection of ecology, physiology, biomechanics, paleontology and oceanography, and take us on a tour of productive temperate ocean waters around the world.

Dave Cade is a postdoc at Hopkins Marine Station.