A humpback whale fuels its 45-foot-long body with tiny shrimp called krill and other small plants and animals called plankton. To gather enough krill for its massive size, the humpback whale lunges forward while opening its mouth to gather a giant mouthful of seawater.
The whale then spits the water back out through plates of baleen that filter out the tiny prey. (Also read: “Mysterious New Humpback Whale ‘Song’ Detected?”)Whales lunge hundreds of times each day, which requires a substantial amount of energy.
“It’s like driving in stop-and-go traffic. All that acceleration and breaking is hard on your fuel economy,” adds Frank Fish, a marine biologist at Pennsylvania’s West Chester University who was not involved in the new study. All this flipper flapping, then, appears to provide a much needed energy boost to heaving that giant body.
Fish notes that before this study, scientists “had looked at humpback flippers like static airplane wings.” (Read how we brought humpback whales back from the brink of extinction.)Like a jumbo jet, it was thought that whales steer by banking with their flippers. The rear flukes—the large appendage on a whale’s tail—provide the thrust, like jet engines.
Source : http://news.nationalgeographic.com/2017/07/humpback-whales-oceans-feeding-flippers/