These Sharks Don’t Have to Keep Moving to Stay Alive: ‘Blew Our Minds’

Despite the popular belief that all sharks need to keep swimming or they’ll die, many species of shark can get along just fine staying still.

Gray reef sharks are the most recent species now recognized as not needing to stay constantly on the move, according to new research in the journal Fish Biology.

These endangered sharks were previously thought to need to always move to maintain the flow of water over their gills, but the research reveals that the little sharks were spotted chilling out motionless on a reef off the Seychelles.

“On routine survey dives around D’Arros we found gray reef sharks resting under coral reef ledges. This is significant because this is not something we believed they could do,” said Robert Bullock, the director of research at the Save Our Seas Foundation D’Arros Research Center and a co-author of the paper, in a statement.

The discovery was “a pure chance encounter that blew our minds,” James Lea, study co-author and CEO of the foundation, said in the statement.

Sharks are often falsely assumed to need to constantly move, as this keeps a fresh supply of oxygenated water flowing over their gills, allowing them to absorb the oxygen into their bloodstream. This is called obligate ram ventilation, as the water needs to be constantly forced over the gills through their movement through the sea.

Other species of fish don’t need to do this. Instead, they can open and close their mouths to force the water over their gills—a process called buccal pumping—allowing them to stop and take a break.

More and more sharks once thought to be obligate ram ventilators are now being identified as buccal pumpers. Until now, gray reef sharks were assumed to ram ventilate, based on their body shape and size, and the habits of their close cousin species.

However, the research shows that the sharks can rest and ventilate their gills for at least 40 minutes. All the resting sharks were facing in different directions, which implies that they weren’t all facing into a current of water and therefore must have been pumping the water over their gills manually.

“Gray reef sharks have been generally considered the stereotypical ram-ventilating shark, unable to rest, so to find them resting really turns the fundamentals of our understanding of these sharks on its head,” Bullock said. “The finding also has…