A new study of minke whales in Antarctica reveals a minimum size limit for whales using a highly efficient “rush-feeding” strategy that enabled the blue whale to become the largest animal on Earth.
Lunge feeding whales rush toward a patch of prey, swallow a massive amount of water, then filter the prey through the baleen plates in their mouths. This strategy is used by the largest group of baleen whales, known as rorquals, which includes blue, fin, humpback, and minke whales.
The ability to swallow large amounts of prey-laden water is essential to bringing this feeding strategy to fruition, and energy efficiency increases with body size. For example, an 80-ton blue whale can swallow a volume of water equal to 135% of its own body mass, while a 5-ton minke whale can swallow a volume equal to 42% of its own body mass.
In the new study, published March 13 in the nature and its evolution, researchers used non-invasive suction tags to monitor 23 Antarctic minke whales in the waters off the West Antarctic Peninsula, tracking their daytime and nighttime foraging behavior as they fed on Antarctic krill. Data from previous studies of humpback whales feeding on krill and blue whales was used for comparison.
said first author David Kidd, who led the study as a postdoctoral researcher at UC Santa Cruz and is now at Naval Station Hopkins at Stanford. “Anything smaller than a mink cannot achieve the foraging rates needed to survive.”
Minke whales are not as well studied as other species of baleen whales, in part because they are difficult to find and tag.
“The data presented in this study represent more information about poorly studied species than ever before, and help us better understand not only species, but the role of baleen whales in ecosystems,” said co-author Ari Friedlender, Professor of Marine Biology, Ari Friedlender. Navy”. Oceanography at the University of California, Santa Cruz. “With so little known about these species being affected by climate change, the better we understand their ecology and behavior, the better we can protect them.”
The researchers observed minke whales’ remarkably high feeding rates, especially at night, when they often fed every 15 seconds or so. Krill come to the surface at night and stay at depths during the day, so feeding during the day requires deep diving, which is less efficient for smaller animals.
“During the day they feed at depths similar to humpbacks and blue whales,” Kidd said, “but their foraging rates are not as high because they are smaller.” “Their feeding rates at night are two to five times that of the day.”
At night, the smaller, more maneuverable minke whales are well-suited to stalking the small, scattered patches of krill on the surface. “When they’re feeding at the surface, they don’t have to hold their breath while diving and they can do the lunge over and over,” Kidd said. “Only at night can they get the high feeding rates they need.”
The study also addresses questions about the evolution of baleen whales and the origins of their large body size feeding strategy. Lunge feeding is thought to have originated first in whales the size of minke whales in today’s Antarctica. This enabled the evolution of whales with massive body sizes, such as blue whales, over the past 5 million years when changing ocean conditions created predictable areas with large patches of prey that could be efficiently exploited by lunge-feeding whales.
“Mine whales represent one extreme, at the small end of the spectrum, of how filter feeding has evolved in ocean predators,” Friedlander said. “Understanding both the maximum and minimum size constraints on the size of the baleen whale really helps us understand how this group of animals evolved and how they influence and are affected by marine ecosystems.”
In addition to Kidd and Friedlander, co-authors on the paper include Cheryl Kahane-Rothert, William Goff, and Jeremy Goldbogen at Naval Station Hopkins. KC Bierlich and David Johnston at Duke University; Jacob Lenski of the University of California, Santa Cruz; and John Kalambokidis at the Cascadia Research Collegiate. This work was funded by the National Science Foundation and the Office of Naval Research.