AILSA CHANG, HOST:
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, HOST:
It's not as easy as you might think. Only 40% of us human mothers are able to recognize our own baby's 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 CAPE FUR SEAL PUPS CALLING)
CHANG: Cape fur seal mothers can recognize their pup's cries as early as two hours after birth.
ISABELLE CHARRIER: They are just the best.
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.
CHARRIER: They have to find each other among thousands of individual and sometimes several hundreds of thousands.
CHANG: To investigate this ability, her team crawled through the sand at a Cape fur seal colony in Namibia, crawling so as not to startle the animals, causing a seal stampede. 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 CAPE FUR SEAL PUPS CALLING)
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 pups called.
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.
(SOUNDBITE OF CAPE FUR SEAL PUPS CALLING)
KELLY: 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 CAPE FUR SEALS CALLLING)
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 CAPE FUR SEAL PUPS CALLING)
CHANG: They found that pups could recognize their own mom's cries just four to six hours after birth, faster than other mammals.
CHARRIER: For us, it was a big surprise.
CHANG: The findings were published this week by The Royal Society.
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, he would be able to hear his mother's voice. So we think it's probably a learning process that start much before the birth.
KELLY: Similar, perhaps, to what happens in humans.
CHANG: (Laughter) So even though seals may have us bested at recognizing our young, it's a good reminder that, even before birth, children are always listening.
(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.
