New research suggests that dolphins rub up against coral for more reasons than scratching a hard-to-reach itch. The cetaceans, which are known to rub against the rough surfaces of coral, take naps in coral beds, and enjoy soaking on sponges along the reef may actually be using the coral to treat their skin ailments.

This new information was published last week in a study co-led by a wildlife biologist at the University of Zurich, Switzerland, Angela Ziltener. “It’s very intensive,” Ziltener says of the dolphins’ interactions with particular corals. “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.”

Using coral as skincare

Dolphin skin, which is smooth and thick, can still be prone to skin conditions like yeast and bacterial infections, scars, or tattoo-like lesions caused by viral pox infections. Global heating seems to only be making these conditions worse.

Ziltener and her team have been monitoring a community of 360 Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the northern Red Sea for over a decade. They observed that the dolphins would line up nose-to-tail to rub themselves against the coral as soon as they woke up and right before they went to sleep. The dolphins’ rubbing also caused the corals to release polyp mucus.

Choosing only certain coral species

The scientists also noticed that the dolphins were particular about which coral species they chose and which parts of their body they were rubbing against them. After running tests on 48 samples of corals, sponges, and coral mucus that were “chosen” by the dolphins, the team found that at least 17 different bioactive metabolites with antibacterial, antioxidative, and estrogen-like hormonal properties, all of which could be used in skin treatments.

The team plans to conduct more research on the topic so that they can figure out which coral’s medicinal properties the dolphins need to treat their skin ailments, and whether these properties have a positive impact on the overall health of the dolphins.

The team also hopes to study the corals ignored by dolphins, to see if they lack the same medicinal properties.

Source study: Cell — Evidence that Indo-Pacific bottlenose dolphins self-medicate with invertebrates in coral reefs