Dolphins Perform Self-Medication by Rubbing Against Corals

A scientist notices a pod of dolphins rubbing themselves against corals for self-medication.

Self-medication in the animal kingdom is not only observed in humans, but also other species such as ants, bees, and parrots. Ants intentionally consume harmful reactive oxygen species (ROS) when exposed to fungal pathogens

Bees infected with intestinal parasites seek nectar high in alkaloids such as nicotine. Parrots eat clay to coat themselves with resin. Angela Ziltener, a wildlife biologist at the University of Zurich, recently observed bottlenose dolphins rubbing against coral to treat their skin problems.

It was 13 years ago in the northern Red Sea in Egypt that Ziltener saw a group of Indo-Pacific bottlenose dolphins approaching the coral. Since then she spent time in the ocean to gain the dolphins' trust so she could get a closer look at their behavior.

Ziltener said the coral-rubbing behavior had not been described before and that the dolphins knew exactly which coral they wanted to use.

Self-Care for Dolphins

When Ziltener and her colleagues were able to get close to the dolphins, they could see which type of coral the dolphins were rubbing against in particular. They were also able to observe what effect this had on both the dolphins and the reef species.

The team found that mucus leaked from the corals as the invertebrate polyps that live in the corals were annoyed by the friction against the corals.

The researchers returned to the lab with coral samples, including some gorgonian coral (Rumphella aggregata), some leather coral (Sarcophyton sp.), and some sponge (Ircinia sp.).

Gertrude Morlock, the lead author of the study and an analytical chemist at Justus Liebig University Giessen, Germany, analyzed the mucus secreted by the corals studied.

The three reef species yielded 17 active metabolites that had antibacterial, anti-oxidative, hormonal, and toxic properties. The researchers hypothesize that the dolphins use the bioactive compounds in the exudates of the coral species to treat their skin.

Marlock further explained that the active metabolites come into contact with the dolphins' skin through repeated rubbing. The metabolites could help the dolphins achieve skin homeostasis and be useful for prophylaxis or accelerating treatment against microbial infections.

Taming Tourism

The research team hopes to further study the behavior to better understand which diseases or body parts the various coral rubs can treat. However, the team is concerned that the dolphins are threatened by increased disturbance from groups of tourists who want to swim recreationally with the animals.

Ziltener pointed out that the tourism industry currently makes a lot of money from swimming with dolphins.

Ziltener works with the Dolphin Watch Alliance, a non-profit conservation organization whose goal is to ethically and financially support projects that aid in the global study and protection of wild dolphins.

She hopes to educate tour operators so that the reefs and the animals that call them home receive the protection they need to support continued research and, most importantly, to ensure the future of the animals.