Dolphins are Self-Medicating with Coral, Study Suggests

The vital importance of coral can’t be underestimated, with nearly a quarter of all marine life depending on healthy coral reefs for shelter and food. Now, scientists have discovered that dolphins may be using them to treat skin infections, ​​adding to evidence that some corals and sponges may also have medicinal properties.

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Credit: Angela Ziltener

Indo-Pacific bottlenose dolphins may use coral to self-medicate their skin conditions, according to a new study published in iScience. 

As part of the research study, a team of biologists at the University of Zurich in Switzerland has been surveying a community of 360 Indo-Pacific bottlenose dolphins in the Red Sea off the coast of Egypt since 2009.

During their observations, they noticed the dolphins queuing up each morning and night to take turns rubbing their bodies against certain corals and sponges. The friction also caused some of the corals to release mucus.

“It’s very intensive,” said Angela Ziltener, one of the study’s lead authors. “They don’t just go through [the coral] – they go up, they come back down again and they rub their belly, their ventral area and the back.”

A bottlenose dolphin in the Red Sea near the southern Israeli coastal city of Eilat. Credit: Tal Shema, cc by-sa 4.0/Wikimedia

She and her team noticed that the dolphins were specific about which organisms they rubbed themselves against, seeking out the gorgonian coral (Rumphella aggregata), leather coral (Sarcophyton sp.), and a sea sponge (Ircinia sp.). The researchers took 48 samples of those seemingly favored by the dolphins and discovered 17 active metabolites with antibacterial, antioxidative, hormonal, and neurotoxic activities. The presence of these bioactive metabolites “accounts for this selective rubbing behavior”, according to the study.

“Repeated rubbing allows the active metabolites to come into contact with the skin of the dolphins,” said Professor Morlock, an analytical chemist and food scientist at Justus Liebig University in Germany and co-author of the study. “These metabolites could help them achieve skin homeostasis and be useful for prophylaxis or auxiliary treatment against microbial infections.”

Dolphins’ smooth, thick skin is susceptible to fungal infections and rashes, with diseases reportedly being aggravated by climate catastrophe. 

Although additional research is needed to determine whether the corals and sponges really do benefit the dolphins’ health, as well as the medical properties of the corals themselves, Ziltener says the find highlights the importance of conserving coral reef systems. 

“This is very valuable work,” Michael Huffman, an expert on animal self-medication at Kyoto University not involved with the research, tells Tess Joose for Science. “I’ve long awaited a really solid study of self-medication in a marine animal species.” 

Scientists collected samples of coral and sea sponge species the dolphins appeared to prefer. Credit: Angela Ziltener

With the majority of dolphin research occurring in captivity or from the surface of the water, the work also shows the importance of studying these aquatic animals in their natural habitat. For Ziltener, her ability to get close to the dolphins was down to years of scuba diving with the dolphins to earn their trust. "You have to be kind of adopted by the dolphins. It took time to actually see all their secrets," she said.

Climate catastrophe, urbanization, and overfishing, are all placing a tremendous strain on the ocean’s coral reefs. Since 1950, over half of the ocean’s living coral coverage has been lost, with estimates that 90 percent of all coral reefs could be gone by 2050. This, in turn, is causing drastic consequences for marine life, coastal communities, and beaches.

As ocean water temperatures continue to heat up, scientists are urgently searching for solutions in the fight to save the coral reefs that are essential to the survival of so many. One technological solution that is hoping to protect these important ocean ecosystems is 3D-printed artificial coral reefs. Learn more here.

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