Self-medication in the animal kingdom is surprisingly widespread. From ants and bees to orangutans, chimps, and – obviously – humans, many organisms have learned to use products from their environment to soothe their ills.
Now it looks as though bottlenose dolphins may have joined the queue at nature’s drugstore, as they’ve been observed lining up to rub themselves against corals in an apparent effort to treat skin problems. The findings, published in Parasitology, come thanks to the commitment of wildlife biologist at the University of Zurich, Angela Ziltener, who took to the water to earn the dolphins’ trust so that she might get an up-close look at their behavior.
Their penchant for rubbing up to corals first became apparent 13 years ago when Ziltener saw a pod of Indo-Pacific bottlenose dolphins getting chummy with coral in the Northern Red Sea, Egypt.
“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,” Ziltener said in a statement. “I thought, ‘There must be a reason.’”
Having been accepted by the dolphins, Ziltener and colleagues could get a look at which corals in particular the dolphins were rubbing against and what effect this was having on both the animals and the reef species. They realized that the abrasive action of scraping against the coral upset the invertebrate polyps that live within it, and that as a result, they were churning out mucus.
Coral samples in hand, the researchers headed back to the lab so that lead author Gertrud Morlock, an analytical chemist at Justus Liebig University Giessen in Germany, could analyze the goods they were secreting. Their haul contained gorgonian coral (Rumphella aggregata), leather coral (Sarcophyton sp.), and sponge (Ircinia sp.).
The trio of reef species yielded 17 active metabolites in the lab which had antibacterial, antioxidative, hormonal, and toxic properties. It seems, like we humans who are partial to putting snail mucus on our face, the dolphins may be making use of the bioactive compounds in the coral species’ exudates to make their skin happier.
“Repeated rubbing allows the active metabolites to come into contact with the skin of the dolphins,” Morlock said. “These metabolites could help them achieve skin homeostasis and be useful for prophylaxis or auxiliary treatment against microbial infections.”
The dolphins’ use of the coral rub station is comparative to showering or brushing your teeth, says Morlock, as the dolphins top up on mucus scrubs throughout the day.
The team hope to continue studying the behavior to better understand what conditions or body parts the different coral rubs can treat but fear the pod and other dolphins are under threat from the increasing disturbance from tourist groups wanting to swim with the animals recreationally.
“The tourism industry makes a lot of money now out of dolphin swimming,” said Ziltener, “…so they are figuring out which reefs they use and disturbing the dolphins if they don’t follow the guidelines for how to approach them in a responsible way.”
Her work with Dolphin Watch Alliance, a conservation group, hopes to educate tour companies so that reefs and those who call them home can receive the necessary protection to support further research and, most importantly, secure the animals’ futures.