Indo-Pacific bottlenose dolphins may rub against corals in order to treat skin conditions, according to a new article by scientists from Switzerland, Germany and Egypt.
In the article, published in the peer-reviewed journal iScience, the scientists described how Indo-Pacific bottlenose dolphins repeatedly rubbed against three distinct types of coral in the northern Red Sea selectively and preferentially.
The dolphins used specific coral for specific body parts based on differences in the properties of the coral and the sensitivity of their body parts. For example, their strong head would be rubbed against harder corals. Dolphins in groups would even queue up and take turns rubbing against coral.
“I hadn’t seen this coral rubbing behavior described before, and it was clear that the dolphins knew exactly which coral they wanted to use," said co-lead author Angela Ziltener, a wildlife biologist at the University of Zurich, in a press release. “I thought, ‘There must be a reason.’”
The scientists found that when the dolphins rubbed against the corals, it caused them to release mucus. Lead author Gertrud Morlock, an analytical chemist and food scientist at Justus Liebig University Giessen in Germany, along with her team analyzed the mucus and found 17 active metabolites with antibacterial, antioxidative, hormonal and toxic activities.
Based on these results, the scientists posited that the dolphins were using the mucus from the corals to medicate their skin in order to regulate their skin's microbiome and treat infections.
“Repeated rubbing allows the active metabolites to come into contact with the skin of the dolphins,” said Morlock in a press release. “These metabolites could help them achieve skin homeostasis and be useful for prophylaxis or auxiliary treatment against microbial infections."