Underwater Pharmacy – Dolphins Scratching Coral Reefs – SWR Knowledge

Dolphins – intelligent marine mammals. There are many interesting facts about marine animals, but researchers have not been clear for a long time why dolphins rub against some of the reefs. Biologists now think they know why.















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Wrapped in a diving suit and equipped with an underwater camera, biologist Angela Zeltner films and captures her dolphins with a camera. What surprised them over 13 years ago: Dolphins head to reefs in a highly targeted manner in order to naturally rub, scratch or sponge themselves.

Obstacle of the Year: Earning the Dolphins’ Trust

But why dolphins have been searching for very specific corals and sponges to rub hasn’t been clear for a full 13 years. The biologist first had to gain the dolphins’ trust in order to know exactly which reef they would choose to scratch. Because without this confidence, the study would have been impossible, says biologist Angela Zeltner:

“Because they are so much faster than us. They can then really slow down and take you with them. But it takes that kind of confidence.”



A mother dolphin shows her calf how to scrub the reef.



press office


Angela Zeltner


Coral produces a strong sludge

Over time, the biologist was able to get up close and personal with the coral species common to dolphins. It soon became apparent that the dolphins’ rubbing against coral had resulted in the production of slime. And a biologist managed to sample this slime: chemist Gertrude Morlock of the University of Giessen examined the samples and was surprised by the result:

“We were surprised by the large number of active ingredients we found.”



Coral species: Rumphella aggregata (Photo: imago images, / imagebroker)

The ‘Rumphellagregata’ coral is also called bush gorgonian. It is one of the common types of coral that dolphins love to rub.


imago pictures



/ imagebroker


Coral slime against skin diseases in dolphins

The research team found a total of 17 different active substances in the coral slime. The research team suspects that some substances have an antibacterial or toxic effect and could specifically help dolphins. According to chemist Gertrude Morlock, dolphins can treat their skin diseases using coral slime.



Dolphins with a skin disease can be treated by coral reefs.  (Photo: Press Office, Angela Zeltner)

Pictured: a dolphin with a fungal infection on its dorsal fin.



press office


Angela Zeltner


And therefore chemist Gertrude Morlock suspects that dolphins treat themselves with coral slime or take good care of the skin so that diseases do not develop in the first place: “Of course they can also be preventive, that is to balance the skin, protective, supportive acting. There are also antioxidants. We all know creams skin with antioxidants.

Small animals must learn to behave

Baby dolphins must first learn how to make contact with the reef. Parents pass on knowledge. Biologist Angela Zeltner has also been able to notice this over and over again. Because the little calves haven’t done that yet. “They watch and notice and then slowly start slipping,” says the biologist. “It seems very funny at first.”



A diver swims alongside a dolphin (Photo: Imago Images/Danita Delemont)

The biggest enemies of the dolphin are large sharks and humans. They are still being hunted. Sea creatures take time to trust humans.


imago pictures



/ Danita Delemont


When rubbing against coral, dolphins do not want to be disturbed by strangers. So dolphins avoid contact with the reef when there are many boats and divers around. This is why the research team is committed to protecting dolphins.

And they are sure: dolphins can do much more than we think today. The fact that dolphins deliberately rub themselves on coral reefs to care for their skin probably won’t be the latest discovery about dolphins.

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