FIN WHALES SWALLOW A BUS-FULL
12.7.07 Enviar esta notaJennifer Viegas
When great whales lunge they swallow about 2,900 cubic feet of krill ’soup.’
WASHINGTON, U.S.; December 7, 2007.- How much can a great whale gulp? Scientists now know the answer. According to new calculations, when lunging toward schools of krill and fish with an open mouth, a single fin whale can engulf up to 2,900 cubic feet of the ocean “soup.”
That’s equivalent to what would fit into a large school bus. After filtering out the water through special plates at the top of its mouth, the whale, which can measure up to 88 feet in length, is left with about 25 pounds of krill.
For decades, researchers have speculated about how much water and food whales can fit into their mouths. The new calculation, along with analysis of whale energy and locomotion, are the first that are based on verifiable scientific testing procedures rather than on educated guesswork. Pyenson points out it’s not easy gathering data on the massive mammals.
“Remember that you can’t get whales to run on a treadmill in a laboratory,” said Nicholas Pyenson, who worked on the research with colleagues Jeremy Goldbogen and Robert Shadwick.
“It’d also be impossible to hold a whale in place for research,” he said, “not to mention the fact that their activity occurs under water and their size makes it next to impossible for a cameraman to hold a camera in the right position for any usable length of time.”
The research, published in this month’s Marine Ecology Progress Series journal, actually used footage from Discovery’s recent “Blue Planet” series.
Pyenson, a paleontologist and University of California at Berkeley Department of Integrative Biology researcher, and his two colleagues input footage from the “Open Seas” episode into a computer program. The footage showed a Bryde’s whale lunge-feeding on a school of fish.
“The footage is extraordinary and is arguably the best for any rorqual (fast-moving lunge feeders),” Pyenson told Discovery News. “It serves as a vital source of information regarding the change in (mouth) gape angle over time.”
The scientists combined this data with information gathered in recent years from “critter cams,” or tiny recording devices stuck momentarily with plungers to the backs of whales. They also took precise measurements of whale skeletons from museum specimens.
Together, the information suggests fin whales feed in a series of lunges, which each last 6-10 seconds. A single dive incorporates up to seven lunges. Given the nutrition in 25 pounds of krill, a whale could meet its daily energy requirements in about four hours of hunting, according to the researchers.
Pyenson likens the open-mouthed lunge technique to a predator taking a bite out of prey, since krill and many fish “school together as though they were one, much larger, organism.”
That could help to explain why the largest marine mammals feed seemingly at the bottom of the food chain. Massed together, a school of krill can provide a nutritious and filling amount of food for whales.
The researchers also determined that the force of each whale lunge creates an enormous amount of drag that “essentially stops the whale dead in the water,” forcing it to accelerate from a resting position, which requires a lot of energy.
Steven Vogel, a professor emeritus of biology at Duke University and the author of numerous best-selling books on biomechanics and animal locomotion, explained that the whale mouth “acts like a gigantic parachute on steroids when it’s open,” causing the whale to lose momentum from its lunge.
“The mouthful of water and krill is so large that it also changes the body shape of the whale, turning an otherwise streamlined swimmer into a slower mass,” he added.
Vogel also said that he too has used film footage during his research. In his case, it was the 1953 Disney nature film classic, “The Living Desert,” which wound up inspiring some of his findings on kangaroo rats and movement in other bipedal jumpers.
(Discovery News)
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