>> Carolyn Wilke, The New York Times
Published: 2022-05-24 16:21:56 BdST
Dolphins may rub on specific corals and sponges to treat their skin, researchers reported Thursday in the journal iScience. These stationary sea creatures may serve as drive-by pharmacies, dispensing a chemical cocktail that could treat bacterial or fungal infections or support skin health. The scientists said cetaceans have not been observed self-medicating before.
Angela Ziltener, a biologist who works at the Dolphin Watch Alliance in Switzerland, spotted this behavior in 2009. Dolphins lined up in front of a coral and each one took their turn, sometimes circling to the back of the line for another go.
The dolphins seemed to have clear preferences — out of hundreds of coral species in the reef, they used a select few, Ziltener said. Sometimes after the dolphins hit up a coral, their skin was stained yellow or green. Knowing that sponges and corals contain an assortment of chemical compounds, Ziltener connected with Gertrud Morlock, an analytical chemist, to investigate whether the dolphins’ behavior could be explained by what’s in the goo these creatures exude.
In 2019, the researchers snipped tiny pieces from two soft coral and one sponge species they had seen dolphins rubbing against in the Red Sea. Combining several powerful techniques, the team sleuthed for substances. Morlock said they found 17 bioactive compounds.
Some of these molecules may serve as immune boosters or sunscreens, said Julia Kubanek, a marine chemist.
She noted that the scientists didn’t report whether dolphins prefer to rub against corals and sponges that contain more bioactive compounds.
Self-medication “seems totally plausible,” said Eric Angel Ramos, a marine mammal scientist. “But equally it’s plausible that they just love to rub against it.”
He suggested testing whether the dolphins get a medicinal benefit from these invertebrates by working with captive animals. They often scratch, bite or otherwise beat up one another, which provides an opportunity to track how dolphins’ skin fares after some coral or sponge skin care.
The research team is working to analyze footage of thousands of dolphin rubs on corals and sponges, Ziltener said. That data could contain clues to whether the dolphins are getting an Rx on the reef. If some of them repeatedly dose themselves, that could bolster the case for self-medicating.