Dolphins are extraordinarily intelligent animals, but they may be even smarter than we realized. They can teach each other new tricks, no human trainers needed.
According to the Atlantic, some wild dolphins have learned how to "tail walk," a technique previously only taught to captive dolphins for aquarium shows.
They learned from the best, Billie the dolphin.
The Atlantic reported that Billie was a wild dolphin who spent three weeks at a Marineland aquarium after being rescued from a polluted harbor. While she recuperated, she was housed with five captive dolphins.
Billie herself wasn't given any training, but she seems to have picked up one trick just by seeing it: the infamous dolphin tail walk.
Billie's is a little imprecise but still good considering she had no formal training.
After her release, and throughout the '90s and 2000s, Billie introduced this behavior to at least 10 other dolphins, according to the Atlantic.
Dolphins have been known to develop skills and traits outside of their usual dolphin behavior in the past, according to the Daily Mail. Some captive dolphins learned how to save their fishy leftovers to bait seagulls. And some wild dolphins began putting sponges on their noses to keep safe from sharp things in the sand as they rooted for food.
But scientists couldn't explain why Billie and the other dolphins would have desired to learn the tail-walking trick, as it's not helpful for important things like mating or gathering food.
Dolphin expert Diana Reiss hypothesized to the Atlantic that it may now be considered a bonding behavior for the dolphins in that area.
If that's the case, though, it doesn't really explain why only the female dolphins bothered to learn the move. Male dolphins aren't ones to shy away from social bonding.
Azula previously reported that they'll even "hold hands" when they swim — although even that is reported to be a breeding strategy, as male dolphins who swim in packs of two or three have a better time finding mates.
After Billie's death in 2009, her many tail-walking proteges kept the tradition alive for a couple more years. According to the Independent, the behavior started to fall from popularity after 2011. Today only two living wild dolphins still perform the trick, but not very often.
Still, Billie showed that dolphins are smarter than they're often given credit for — as she was able to mimic other dolphins without any training and later "teach" that trick to more wild dolphins.