But as soon as the cephalofoil was tilted up or down, the force quickly came into play, enabling a rapid ascent or descent. This helps to explain why hammerheads are “much more maneuverable than a typical shark,” said Dr. Parsons, who thinks the skill may help them snap up food from the sea floor.

The researchers also measured how much drag the cephalofoils produced. The winghead shark, which has the largest hammer, appears to be dealing with “20 to 40 times the amount of drag” as a typical fish, Dr. Parsons said.

Such a head, he added, seems like “a pain in the butt,” although the benefits it provides must outweigh the costs.

Analyzing so many species is “a real push forward” for hammerhead hydrodynamics, said Marianne Porter, a biologist at Florida Atlantic University who was not involved with the research. “We can start to study the variation among them.”

But, she added, “there are some limitations with computational models.” In the real world, sharks swim with their whole bodies, through constantly changing ocean conditions. When you are trying to recreate such things in models, and focusing on one body part at a time, “things get muddy really fast,” she said. (Indeed, in a similar study published in 2018, Dr. Porter found that the hammerhead body overall does produce lift.)

“The hammer is, at all angles of attack, producing a lot of drag,” Dr. Parsons said in reply. “But it might be possible to recover some of that lost momentum by appropriately placed fins and structures” elsewhere on the shark.

He said he hoped that other researchers would continue to investigate the issue: “The best research questions are the ones that generate 10 more.”

source: nytimes.com


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