ARI SHAPIRO, HOST:
This year we've shared the mic with many talkative animals and stories about the unique ways they communicate.
AILSA CHANG, HOST:
And today we're rounding up some of our favorites, starting with this piece of friendship advice that NPR's Kelsey Snell and I learned from dolphins.
KELSEY SNELL, BYLINE: 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)
CHANG: 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 exchanged between three dolphins. The researchers gave them names - Kooks, 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: 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 SVEN LIBAEK'S "SOUNDS OF THE DEEP")
CHANG: OK, so if dolphins haven't inspired you to up your communication game, here's a story co-host Mary Louise Kelly and I shared about another species, one with bonding skills that blow us all out of the water. Now, here's a question for all the parents out there. Would you be able to pick your child's cry out of a lineup?
MARY LOUISE KELLY, BYLINE: It's not as easy as you might think. Only 40% of us human mothers are able to recognize our own babies' cries 24 hours after birth. That's according to one study. Sheep take 24 hours as well. Goats take 48 hours to pick out the bleats of their own kids.
CHANG: But a new study suggests that a different mammal has the rest of us beat.
(SOUNDBITE OF SEALS BARKING)
CHANG: Cape fur seal mothers can recognize their pups' cries as early as two hours after birth.
KELLY: Isabelle Charrier is a researcher at the French National Centre for Scientific Research. She had an inkling these seals develop rapid vocal recognition because they are packed together in gigantic colonies.
ISABELLE CHARRIER: They have to find each other among sometimes several hundreds of thousands.
CHANG: Her team crawled through the sand at a Cape fur seal colony in Namibia. Soon after seals gave birth, they would train their microphones on the pups to record their calls.
KELLY: Then they played back those recordings for the mothers through a speaker.
(SOUNDBITE OF SEAL PUPS CRYING)
KELLY: When they played a call from someone else's pup...
CHARRIER: The female would not respond.
CHANG: But when they played the mother her own pup's call...
CHARRIER: They check their pup. They smell it to say, OK, I can hear your voice, but you are just in front of me. So they are a bit confused. So they call back, but then they check if the pup they have in front of them is theirs.
CHANG: It wasn't just the mothers who recognized calls. The researchers did the same experiment in reverse, playing mothers' calls to the pups. And when they played calls from someone else's mom...
(SOUNDBITE OF SEAL GROWLING)
CHARRIER: They don't even look because they are very young. And for them, it seems it's quite difficult to localize the sound source. Then when you play back the call of their mothers, then they become more interested, and most of the time, they call back.
(SOUNDBITE OF SEAL PUP BARKING)
CHANG: They found that pups could recognize their own moms' cries just four to six hours after birth, faster than other mammals.
CHARRIER: For us, it was a big surprise.
KELLY: Charrier says the fact that pups develop this ability so early without hearing many calls from their mother after birth means they must be listening from inside the womb.
CHARRIER: So during all the pregnancy, it would be able to hear its mother's voice. So we think it's probably a learning process that starts much before the birth.
KELLY: Similar, perhaps, to what happens in humans.
CHANG: So even those seals may have us bested at recognizing our young, it's a good reminder that even before birth, children are always listening.
(SOUNDBITE OF MAREN MORRIS SONG, "GIRL")
SHAPIRO: Finally, Mary Louise and I got some pointers on karaoke from bats.
KELLY: The vocal range of most humans is pretty limited - three octaves, maybe, maybe four or five if you're really good, like Mariah Carey.
(SOUNDBITE OF SONG, "EMOTIONS")
MARIAH CAREY: (Singing) You make me feel so high.
SHAPIRO: But even Mariah Carey wouldn't stand a chance against a bat. They can pull off seven octaves.
COEN ELEMANS: They sort of make very low-frequency calls and make echolocation calls, and they span together, like, seven octaves.
SHAPIRO: Coen Elemans is with the University of Southern Denmark. He and his colleagues used ultra high-speed video, filming up to a quarter million frames a second to study what's going on in bats' vocal tracts.
KELLY: The idea was to study how bats make the super-high-pitched echolocation calls that they use to find prey. But when the scientists looked at the other end of the register, at the low calls that bats make, they discovered that bats seemed to recruit a different part of their vocal tract, which they say is analogous to how humans pull this off...
(SOUNDBITE OF SONG, "SLOWLY WE ROT")
OBITUARY: (Singing) Fight them all in a living hell. Slowly rot, and you die.
KELLY: ...Or this...
(SOUNDBITE OF SONG, "SHAMAN")
HAYK ROMIA: (Singing in non-English language).
ELEMANS: Like death metal singing or throat singing. In humans, these folds have been called the false vocal folds because they have no function in normal speech, so they don't seem to do anything - only in the sort of some extreme forms of singing.
SHAPIRO: Now, to be clear, the low sounds the bats make do not sound like death metal or throat singing. Here's a sample.
(SOUNDBITE OF BAT CLICKING)
SHAPIRO: Remember; this is low for a bat. Slowed down 50 times to hear it better with human ears, it sounds kind of sinister.
(SOUNDBITE OF PITCHED-DOWN BAT CLICKING)
KELLY: The scientific findings appeared in the journal PLOS Biology, and while we could not ask the bats what it is like making those low-register sounds, we could ask some human practitioners of the death metal growl.
(SOUNDBITE OF SONG, "SLOWLY WE ROT")
OBITUARY: (Singing) Dead to all, fighting as you're slowly...
JOHN TARDY: I mean, it's from your abdomen to your chest to your legs to, obviously, a lot of your throat. But it is a full-body thing for me.
SHAPIRO: John Tardy is lead singer of the death metal band Obituary, heard there on the track "Slowly We Rot."
KELLY: Chase Mason of the group Gatecreeper says pain is just part of the process for him.
CHASE MASON: I think that when I can feel that my vocal cords are getting kind of shredded or beat up, that it sounds better.
KELLY: His advice for listeners who want to try the death metal growl...
MASON: Go into their closet and just, like, try to yell as loud as they can just so you can get used to how it feels.
SHAPIRO: I'm going to leave that to the bats.
(SOUNDBITE OF SONG, "FROM THE ASHES")
GATECREEPER: (Singing) Wandering through chaos, scarred from nightmares. Transcript provided by NPR, Copyright NPR.
