Who doesn’t like a bath scrub? Dolphins certainly do: They are known for being smart, playful, tactile animals, and they enjoy rubbing against rough surfaces, napping in coral beds, and soaking up sponges like guests at an underwater spa.
Dolphins may get more out of their bath scrub than just relaxation and leisure. A study published today suggests bottlenose dolphins can self-medicate their skin conditions using corals, adding to growing research into their previously untapped medicinal properties.
“It’s very intensive,” said Angela Ziltener, one of the lead authors of the study, about dolphin behavior with certain corals. “They don’t just go on” [the coral] – they go up, they come down again and they rub their stomach, their stomach area and the back.”
Dolphins have thick, smooth and resilient skin, but can be prone to skin conditions such as yeast and bacterial infections, scarring, or tattoo-like lesions caused by viral smallpox infections. These conditions appear to be exacerbated by global warming.
Ziltener, a wildlife biologist at the University of Zurich, Switzerland, and her team studied a community of 360 Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the northern Red Sea since 2009. They noticed that the dolphins often lined up nose to tail to rub against corals as soon as they woke up and just before going to sleep, as if they were showering for the day. In addition to a mechanical friction, the dolphins also caused the corals to release polyp slime.
The team also noted that the dolphins returned to the same coral species, and they seemed to carefully choose which parts of their bodies to rub. They conducted lab tests on 48 samples of corals, sponges and coral slime “chosen” by the dolphins, including the gorgonian coral. Rumphella aggregatesthe leather coral Sarcophyton sp. and the sponge ircinia sp.
The results, published in the journal iScience, revealed at least 17 different bioactive metabolites with antibacterial, antioxidant and estrogen-like hormonal properties, all of which could be useful in skin treatments.
The compounds are not commonly used in antibiotics for humans or animals, but a growing body of research shows that some corals and sponges have medicinal properties, including antimicrobial.
“Such metabolites are helpful when you have an infection,” said Gertrud Morlock, an analytical chemist at Justus Liebig University Giessen in Germany, and a lead author of the study. “If the dolphins have a skin infection, these compounds could have something like a healing property.
“If you think about it, they have no other options. If they have a skin problem, what can they do?”
The authors note that further research is needed to show what medicinal properties the dolphins need to treat certain ailments, and whether these properties have a measurable, positive impact on the health of the cetaceans.
Learning more about the dolphin’s social network and demographics can help with this. Tracking individual dolphins exhibiting the behavior and seeing if they have fewer skin diseases or less mortality compared to the rest of the group would strengthen this argument, according to Sarah Powell, a former marine biologist who studies how dolphins transmit their skin diseases. but was not involved in the investigation.
Previous research has shown that dolphins like to use coral sponges as foraging tools. “I don’t think it’s such a range that dolphins would use corals and other plants in their environment for other purposes,” Powell said.
Stephanie Venn-Watson, a marine biologist who studies dolphin health and longevity and was also not involved in the study, said: “Since dolphins are naturally playful and tactile animals that like to rub, it’s difficult to be sure that the dolphins use the corals for medicinal purposes.”
A next step in proving the connection would be to show that corals ignored by dolphins lack the same medicinal properties, she said. “This is a nice science-driven itch to get scratched.”