KELSEY SNELL, HOST:
You know those friends who live far away, but you still stay in touch? You can't really hug, so you call or text them instead. Well, dolphins do something sort of similar.
(SOUNDBITE OF DOLPHIN WHISTLING)
AILSA CHANG, HOST:
That, my friends, is whistling. A new study found that the male bottlenose dolphins in Western Australia whistle to the other male dolphins they don't have strong bonds with.
SNELL: University of Bristol marine biologist Emma Chereskin is the lead author of the study. She explains that male bottlenose dolphins have an alliance structure. They have their closest circle where the bonds are strong.
EMMA CHERESKIN: They often use physical touch, so rubbing their fins together, swimming side by side.
CHANG: Then there is another circle where the bonds are weaker and they don't use as much physical touch, but they do whistle to identify themselves and to keep alliances intact. In other words, they bond at a distance. Sound familiar?
(SOUNDBITE OF DOLPHINS WHISTLING)
SNELL: That was a whistle exchange between three dolphins. The researchers gave them names - Kooks (ph), Spirit and Guppy.
CHERESKIN: They're saying, hi, I'm Kooks. I'm right here. And then Spirit would reply, hi, I'm Spirit. I'm also right here. And then Guppy gets in on it towards the end. He's saying, hi, I'm Guppy. I'm also here.
CHANG: The study tests the social bonding hypothesis of Robin Dunbar. He proposed that animal vocalizations evolved as a form of vocal grooming to replace physical grooming. Karl Berg from the University of Texas Rio Grande Valley says this study advances that hypothesis.
KARL BERG: These dolphin groups can be in really large groups in the dark ocean where visual communication isn't going to be possible. It makes sense that this vocal communication system is very important to them.
SNELL: Study author Emma Chereskin says it shows just how complex animals can be.
CHERESKIN: Humans are kind of at fault for thinking humans are the only complex social animals that there are. And I feel like sometimes we don't give enough credit to the animal kingdom for just how complex these social lives are.
SNELL: So maybe the next time you want to get in touch with a long-distance friend instead of a text...
CHANG: Maybe just whistle.
(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.
