I have a vivid childhood memory of sitting under the Blue Whale model hanging in the Natural History Museum in London, eating an ice cream and wondering “How in the world did that whale get so big?” These days we are closer to knowing the answer. Over the past several years, a group of researchers have been studying how blue whales eat to better understand how such a big animal can survive on such small food.
Blue whales are in a family of whales that have evolved comb-like baleen and large mouths to gulp huge volumes of water and then sieve out tiny prey—small crustaceans called krill or fish that are their main food source. Using small, state-of-the-art suction-cup tags and new visualization tools, we can now understand the underwater movements of these ocean giants and how they are able to consume up to one ton of food each day!
We recently discovered that blue whales, the largest animal to have ever lived on planet Earth, can feed by conducting 360 degree rolls while opening their cavernous mouths to lunge into an unsuspecting patch of krill. As the whale approaches a prey patch, it rolls more than 180 degrees onto its back, lunges with mouth agape, and then continues to complete the full roll as it closes its mouth full of prey-laden water. This maneuver is driven by several powerful fluke strokes and by tilting its pectoral flippers to help guide the whale through this energetically costly maneuver.
The energy seems to be worth it: this behavior may improve the whales’ chances of engulfing the most krill possible in a single gulp. Krill have evolved ways to escape from predators, and blue whales are easier for them to spot than anything else in the ocean given their enormous size. However, if the blue whale feeds by coming up from dark water below the krill, it may be able to avoid being detected until the last moment. Additionally, the roll may help the whale see and corral the krill better than a straight-on attack. Blue whales have eyes on either side of their heads, and rolling would allow them to see the patch with both eyes and help make the ambush as accurate as possible.
While we have not observed such dramatic rolling maneuvers by other baleen whales, we still know very little about how these ocean giants feed, and we expect to keep researching these incredible animals to learn new and valuable information on how they live. One thing is for sure: whales are big because they are really good at what they do!
Editor's note: This was written in conjunction with:
Jeremy A. Goldbogen, PhD is a post-doctoral researcher with the Cascadia Research Collective in Olympia, WA. Dr. Goldbogen’s research has helped elucidate the functional morphology and biomechanics of how baleen whales feed. His work has been among the first to demonstrate the underwater kinematics of lunge feeding in baleen whales and the energy required to perform these unique maneuvers.
Brandon Southall, PhD is President and Senior Scientist for Southall Environmental Associates, Inc. based in Aptos, CA and a Research Associate with the University of California, Santa Cruz (UCSC). He is currently involved in research projects to measure behavioral responses of free-ranging marine mammals to various human sounds, including military sonar, and hearing and the effects of impulsive noise on hearing in seals. He also serves as a technical advisor to international organizations related to understanding and mitigating impacts of conventional and alternative offshore energy development.