Dolphins treat infections by ‘cleaning themselves against coral’
QUEUING at the chemist might seem a uniquely human activity, but scientists have found that dolphins also line up at reefs to get their flippers on medicinal corals and sponges.
The phenomenon was first observed 13 years ago by biologists from the University of Zurich, in the Red Sea off the Egyptian coast, but researchers were unclear what the creatures were doing.
The team noticed that a pod of Indopacific bottlenose dolphins would queue nose-to-tail and take turns to rub themselves against corals. The rubbing often happened after a nap, and the animals were curiously specific about the corals and sponges they chose.
After years of studying the behaviour, the team realised that the dolphins were agitating the tiny marine invertebrates that make up the coral community, causing them to release medicated mucus.
“I hadn’t seen this coral rubbing behaviour described before, and it was clear that the dolphins knew exactly which coral they wanted to use,” said co-lead author Angela Ziltener of the University of Zurich.
“I thought, there must be a reason. It’s almost like they are showering, cleaning themselves before they go to sleep or get up for the day.” When the team analysed samples of coral and sponges they found 17 active metabolites with antibacterial, antioxidative, hormonal, and toxic activities, which they think the dolphins use to treat infections.
“Repeated rubbing allows the active metabolites to come into contact with the skin of the dolphins,” said Prof Gertrud Morlock, an analytical chemist and food scientist at Justus Liebig University Giessen in Germany.
“These metabolites could help them achieve skin homeostasis and be useful for prophylaxis or auxiliary treatment against microbial infections.”
The team now want to identify which selected corals and sponges are being used for specific body parts.
Many animals use plants to selfmedicate and traditionally farmers would keep a “hospital field” full of medicinal herbs where they would place sick animals and newborns.
Dogs will often eat grass when they have an upset stomach or a parasite because it helps them to vomit.
Some animals, including red and green macaws, eat clay to aid digestion and kill bacteria, while female woolly spider monkeys in Brazil add plants to their diet to increase or reduce fertility.
Pregnant elephants in Kenya have been known to eat the leaves of certain trees to induce delivery.
Chimpanzees in Tanzania swill aspilia leaves in their mouths to release toxins that kill parasitic gut worms and relieve constipation and more than 200 species of birds aggravate ant nests so they will be sprayed with formic acid, which they used to treat lice.
Brown bears have been known to make a paste from spit and osha root, which can soothe insect bites.
The science of self-medicating animals is known as zoopharmacognosy and many researchers believe humans could discover new medications by studying which plants are selected.