Thanks to Linode Cloud Computing for supporting this episode of SciShow.

You can go to linode.com/scishow to learn more and get a $100 60-day credit on a new Linode account. [♪ INTRO] Dolphins are some of the most sophisticated animals on this planet. They have big, complex brains, not to mention advanced social and learning skills.

So we can relate to dolphins in a lot of ways. But until recently, one of their behaviors had scientists scratching their heads. Certain bottlenose dolphins would regularly brush up against corals and sponges on the seafloor.

They'd even line up and take turns to do it. And scientists weren't quite sure what to make of that... until they figured out that these dolphins might be performing a skincare routine. Now, researchers had seen this kind of behavior before from other marine mammals, like killer whales and beluga whales.

Some thought these creatures were basically exfoliating, but no one had really gotten to the bottom of what this behavior was all about. So, when scientists out in the Indo-Pacific started observing bottlenose dolphins doing the same thing, they decided to look into it. Because it definitely didn’t look like an accident.

The dolphins didn’t just casually brush against a coral while they were hurrying on their way somewhere. Entire groups of them would pick out a coral or a sponge and then line up and patiently wait their turn to swim over it. Over the years, various scientists observed this kind of behavior at different times and in different places.

So they really wanted to figure out what it was all about. To get to the bottom of this question, researchers started taking notes on the dolphins’ behavior. They noticed that sometimes, dolphins would slide between the branches of corals, letting their whole bodies brush against them.

Other times, when dolphins encountered corals and sponges that were more compact, they would just push a single body part against them, like their heads. Scientists also noticed that the dolphins weren’t just interested in any old coral. They seemed to seek out three specific species of underwater invertebrates: gorgonian corals, leather corals, and a specific type of sponge.

As the dolphins pushed or brushed against them, some corals would secrete mucus that would stick to the dolphins. In some cases, dolphins would actually take corals into their mouths and shake their heads to make a brightly colored substance fly out. It would form a cloud around the dolphin, eventually settling on its head and neck.

So scientists began to suspect that these secretions were actually what the dolphins were after. The question was why? A 2022 study tried to answer that by looking at the chemical composition of the secretions.

The authors hypothesized that the dolphins were using the secretions to protect their skin against bacteria or other microbes. So, in one experiment, they took samples of the secretions from each of the three invertebrates that dolphins seemed to like. Then they extracted chemical compounds from these samples.

Finally, they added these compounds to cultures with two different kinds of bacteria to see how the bacteria would react. Some of the compounds did nothing, but others killed the bacteria. In other words, they were antibacterial.

In this study, the scientists only tested the compounds on two bacterial species, because they didn’t have enough samples to run a whole array of tests. So, it’ll take more research to find out just how many kinds of bacteria and microbes are affected by the compounds in these secretions. But based on what they found so far, the authors think that these compounds could help dolphins protect their skin.

Now, since this study focused mostly on chemical compounds and not so much on dolphin behavior itself, it’s still hard to say how much dolphins understand what they’re doing. It’s possible that dolphins are intentionally self-medicating, using the secretions from these corals and sponges to either prevent bacterial infection, deal with an existing infection, or improve their skin quality. But they also might just like how it feels.

Any benefits from the compounds might just be a lucky perk. Whatever the reason dolphins do this, they seem to teach the behavior to their young. Dolphin calves aren’t born with an instinct to brush against coral, and they’ll often hang back while older dolphins do it.

But over time, they adopt the behavior too as well. Unfortunately, pinning down exactly why dolphins do this could be tricky because reefs are fragile ecosystems, so going into them to extract samples from corals and sponges could cause damage. That ends up limiting how many samples can be extracted, like in this study, and what kind of research is possible.

But whether these creatures are performing medical care for their skin or just practicing a soothing behavior, this study gives us a fascinating look at these bottlenose dolphins. And it shows it’s possible that these clever animals understand even more about the world than we thought. Either way, it’s more affordable than our skincare routines.

And if you’re a price-conscious consumer, you’ll appreciate how transparent Linode Cloud Computing is with their prices. Linode is here to make cloud computing understandable and accessible for everyone. A big part of what makes them accessible is their pricing.

Linode provides a price calculator to estimate your cloud costs and compare their prices with other providers before you sign up. That way you know you’re making the right choice for you and your finances. They have transparent pricing lists for each of their packages available on their website.

And once you sign up for one, you can switch to another any time you want, to make sure you only pay for what you use. But one thing that you won’t find on their website is the $100 60-day credit that you can earn toward a new Linode account by clicking the link in the description or heading to linode.com/SciShow. So you can go to linode.com/SciShow for an even more affordable cloud computing setup.

Thank you to Linode Cloud Computing for supporting this SciShow video and thank you for watching! [♪ OUTRO]