Blue whales, the largest creatures to have evolved on the planet, are tagged during summer 2019 in the Eastern Pacific off the coast of central California by the study's research team. Through an analysis of 10,000 whale feeding events, the research team found that the body size of all whales is limited by the availability of their prey, but only filter-feeding whales have evolved a feeding strategy that rewards and drives them to achieve the largest body sizes to have ever evolved on Earth. The team's findings are reported online Dec. 12 in the journal Science.
Blue whales, humpbacks and other filter-feeding whales use baleen--rows of flexible hair-like plates in their mouths--to strain krill and other small prey from ocean water. For filter-feeding whales, large size is no impediment to foraging: blue whales, fin whales and humpback whales, the largest whales in this study, achieved greater energy payoff during feeding events than any other whale in the study. Filter-feeding whales feed on small but very abundant krill prey that flourish at high population densities for short periods of time in specific parts of the world. As a result, the researchers who conducted the study speculate that the seasonal availability of their abundant prey is what ultimately limits size in today's filter-feeding ocean giants like fin whales and blue whales.