Why do dolphins rub against corals?

When you have a rash, you go to the doctor or the pharmacy and you may come out with an ointment as a remedy. Indo-Pacific bottlenose dolphins also suffer from skin conditions, but get their medication by lining up to rub against coral. A new study published in ‘science’ shows that these marine invertebrates have medicinal properties, suggesting that dolphins use them to cure skin conditions such as fungal infections.

thirteen years ago, angela ziltener, a wildlife biologist at the University of Zurich, Switzerland, first observed a pod of dolphins skimming against coral in the northern Red Sea off the coast of Egypt. She and her team noticed that the dolphins were choosy about which corals they rubbed against and wanted to understand why. “I hadn’t seen this behavior before, and it was clear the dolphins knew exactly which coral they wanted to use.”says the researcher. She thought there must be a reason.

Since Ziltener is a diver, she was able to study the dolphins up close. It took her some time to gain the trust of the pod, but once the animals allowed her to visit them regularly, she and her colleagues were able to identify and sample the corals the dolphins rubbed against. The researchers found that by repeatedly rubbing against corals, Indo-Pacific bottlenose dolphins stirred up the tiny polyps that make up the coral community, and these invertebrates released mucus. To understand what properties the mucus contained, the team collected samples from the coral.

Dolphins’ favorite corals

Gertrud Morlock, an analytical chemist at Justus Liebig University Giessen in Germany, and her team studied samples of the dolphins’ favorite corals and sponges (Rumphella aggregata, Sarcophyton sp., Ircinia sp..), with high resolution mass spectrometry and other techniques and found 17 active metabolites with antibacterial, antioxidant, hormonal and toxic activities.

This discovery of these bioactive compounds led the team to believe that mucus from corals and sponges serves to regulate the dolphin skin microbiome and treat infections. “Repeated rubbing allows the active metabolites to come into contact with the dolphins’ skin”Morlock explains. “These metabolites could help them achieve skin homeostasis and be useful for prophylaxis or ancillary treatment against microbial infections”he points out.

cleaning before sleeping

The reefs where these corals are found are important places for the local populations of dolphins. They go there to rest and have fun. “Many people don’t realize that these coral reefs are bedrooms for dolphins and also play areas”Ziltener says. Between naps, dolphins often wake up to perform the coral-rubbing behavior. “It’s almost as if they were taking a shower, cleaning themselves before going to sleep or getting up”it states.

Since he began researching dolphins in Egypt in 2009, Ziltener has noticed a disturbing trend. “The tourism industry makes a lot of money now from swimming with dolphins. People dream of swimming with them, so they’re finding out what reefs they use and bother these mammals if they don’t follow guidelines on how to approach them responsibly.”, He says. For this reason, he has formed Dolphin Watch Alliancea conservation group that educates tour guides, tourists and the general public on how to provide tourists with safe experiences for these mammals, and has pushed for the reefs to become protected areas.

The researchers hope that as long as the reefs remain a safe place, they can continue to study coral rubbing and identify which selected corals and sponges are used for specific body parts.

Font: ABC

Reference article: https://www.abc.es/ciencia/abci-delfines-hacen-cola-para-fritarse-contra-corales-202205192011_noticia.html