Dolphins use corals and sponges as medicine – to treat their skin.

Science magazine takes a deep dive on the medical lives of dolphins, who appear to be intentionally using corals and other stuff growing on the reef as antibiotic treatments for itchy skin:

Enter Angela Ziltener, a wildlife biologist with the University of Zürich and the conservation nonprofit Dolphin Watch Alliance. Since 2009, Ziltener has scuba dived in Egypt’s Red Sea among a population of 360 Indo-Pacific bottlenose dolphins (Tursiops aduncus), gaining their trust and observing their behavior up close.

Over the years, she noticed the animals rubbing up against certain corals and sponges. The behavior wasn’t random: The dolphins rubbed their heads on some corals, scraped their bellies on others, and avoided some species altogether (see video, above). Adult dolphins would queue up to rub, whereas the younger members of the group watched closely and slowly began to mimic their actions.

It seemed like the dolphins were getting more than just a good back scratch, Ziltener says. Not only were they selecting specific corals, but as they rubbed, mucus coatings puffed off the corals and sponges, clouding the water and coloring the dolphins’ skin. “They’d get yellowish or greenish,” Ziltener says.

To find out whether coatings from the corals’ mucus had medicinal properties, Ziltener teamed up with Gertrud Morlock, an analytical chemist at Justus Liebig University Giessen. The duo took tiny samples of mucus from the dolphins’ three preferred rubbing surfaces: gorgonian coral (Rumphella aggregata), leather coral (Sarcophyton sp.), and a sponge (Ircinia sp.).

The corals and sponge coatings contained 17 different biologically active compounds that had antibacterial, antioxidative, or hormonal properties.

You can read more about the pair’s research here, in iScience.