Dolphins may be known as the “dogs of the sea”, but they’re far brighter than your average Labrador – and a lot more surprising. A study published by biologists at the University of Zurich suggests bottlenose dolphins use coral reefs as medicinal scrubs, lining up to patiently scour their bodies, as if using antibacterial wipes.
“It’s very intensive,” says Angela Ziltener, one of the study’s authors. “They don’t just go through the coral – they go up, they come back down again and they rub their belly, their ventral area and the back.”
Here are a few more things to know about the good, bad and occasionally ugly world of dolphins.
1. They hold grudges
Dolphins might be some of the most sociable animals in the sea but, according to researchers at the University of Bristol, their loyalty extends only as far as helping those that have come to their aid in the past. If a dolphin helps another in danger and the latter survives, it’s likely the beneficiary will remember and repay the favour. But if a dolphin abandons its comrade, it’s unlikely the dolphin in danger will help that negligent member of the pod in future.
2. They sleep with one eye open
A dolphin is only ever half-asleep – and intentionally. When they rest, the left eye will be closed while the right half of the brain sleeps, and vice versa. This is known as “unihemispheric sleep”, and researchers believe it gives them the ability to stay constantly alert for at least 15 days straight.
While seemingly sleep-deprived, dolphins have been observed to perform with near-perfect accuracy, using echolocation to monitor their surroundings while “asleep”, and continuing to breathe at the surface. And it may well be longer: 15 days was simply the length that particular study, conducted by the National Marine Mammal Foundation in 2012, lasted.
3. They have proper conversations
All that distinctive clicking and whistling suggests that dolphin communication is more advanced than many animals, but we now know they may be having full conversations.
In 2016, researchers at Karadag nature reserve in Ukraine recorded two Black Sea bottlenose dolphins, Yasha and Yana, “chatting” in a pool. A dolphin brain is larger and more complex than a human’s, and Yasha and Yana were seen to listen to one another without interruption before replying with an original phrase.
“This language exhibits all the design features present in the human spoken language,” says Dr Vyacheslav Ryabov. “This indicates a high level of intelligence and consciousness.”
4. They ‘play’ with other animals
A bizarre thing happened in the Tijamuchi river in Bolivia one day last August. There, the long-snouted Bolivian river dolphins can be seen, but you’re lucky to spot them out of the water for long.
On this particular day, however, biologists saw not just two dolphins with their heads above the surface for a long time, but they were carrying a Beni anaconda - an apex predator - in their mouths, as dogs might a large stick in the park.
The behaviour lasted for some seven minutes and hadn’t been seen before, but it’s thought the dolphins were playing.
5. They could help us to understand Alzheimer’s
In 2019, researchers at the University of Miami and the Rosenstiel School of Marine and Atmospheric Science started looking into the link between Alzheimer’s in dolphins and humans. They discovered that the brains of beached dolphins show signs of beta-amyloid, the toxic protein that many researchers believe leads to Alzheimer’s symptoms, and that the dolphins had been exposed to cyanobacterial blooms that came from toxic algae.
In all, the conclusion was that avoiding certain types of seafood (or at least eating it in moderation) and making sure drinking water is clean could mean it’s less likely we’ll harm our brains. More research is being done, however.
The Daily Telegraph
