Risky Behavior: Fish Rub Against Sharks, Scientists Say It Could Be To Exfoliate [Watch]

Why would fish deliberately rub their bodies against their predators? This risky behavior may actually play an important role in aquatic animals, a team of researchers has found.

It seems counterintuitive, but some fish actually go close to sharks and even rub their bodies against them. The behavior has been observed before as well. However, a team of researchers has now found that this may be a more widespread and important activity than previously thought, the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science noted in a news release.

For their study, published in the journal Ecology, The Scientific Naturalist, the researchers looked at witness reports, photos, videos and drone footage of fish chafing their bodies against a shark's skin and found 47 instances of the behavior at various locations around the world.

"They recorded 12 fin fish chafing against eight different species of shark, including great whites," UM noted.

In a video shared by the team, one can clearly see several instances where the fish aren't just swimming close to the sharks, but are actually rubbing their bodies against the predators' skin. The footage even caught silky sharks also exhibiting the behavior, this time rubbing up against a much bigger whale shark.

The events lasted from eight seconds to 15 minutes, UM noted, adding that the number of fish that engaged in the behavior ranged from just one to more than 100 at a time.

"While chafing has been well documented between fish and inanimate objects, such as sand or rocky substrate, this shark-chaffing phenomenon appears to be the only scenario in nature where prey actively seek out and rubs up against a predator," study co-lead Lacey Williams, of UM Rosenstiel School, said in the news release.

So why are the fish engaging in this seemingly risky behavior? It's possible they are doing this for the simple reason of exfoliation. Parasites and bacteria can be found on the surfaces of all organisms and in most cases, the hosts have developed their own ways of ridding themselves of these ectosymbionts.

In the case of the fish, it's possible they are taking advantage of sharks' skin. This is because shark skins have tooth-like scales known as denticles, study co-author Neil Hammerschlag explained.

The V-shaped denticles help the sharks swim faster and more quietly because they help decrease turbulence and drag. In fact, some Olympian swimsuit designs have mimicked this feature to help improve swimmers' speed. Denticles also give sharks' skin a sandpaper-like texture that may possibly be perfect for other fish to exfoliate themselves.

"We suspect that chafing against shark skin might play a vital role in the removal of parasites or other skin irritants, thus improving fish health and fitness," Hammerschlag said.