ARI SHAPIRO, HOST:
Some wild African elephants have names given to them by researchers, names like Margaret, Marie and Desert Rose. Researchers have been asking whether these elephants also have elephant names, names they use when they're talking to each other. NPR's Nell Greenfieldboyce reports one team went looking for answers in elephants' low rumbles.
NELL GREENFIELDBOYCE, BYLINE: The inspiration for this elephant study came from bottlenose dolphins. Mickey Pardo is a researcher at Cornell University. He says these wild dolphins have a unique signature whistle that they make all the time to kind of broadcast their identity.
MICKEY PARDO: And sometimes another bottlenose dolphin will imitate somebody else's signature whistle in order to get their attention, so effectively calling them by name.
GREENFIELDBOYCE: He wondered if elephants might do something similar. He figured that if elephants did use names, those names would be somewhere in their deep rumbles. Elephants rumble to each other a lot.
PARDO: When they're greeting their family members, when they're trying to stay in touch with family members over long distance, when they're trying to figure out where to go as a group, just all sorts of different contexts.
GREENFIELDBOYCE: These are complex, low frequency rumbles. Most of it's beyond the range of human hearing, but just to give you the idea, here's an elephant that the researchers call Frieda rumbling to an elephant that they call Donatello.
(SOUNDBITE OF ELEPHANT RUMBLING)
PARDO: And it just doesn't sound as loud or clear to us as it would to an elephant.
GREENFIELDBOYCE: Pardo and some colleagues recently got ahold of over 400 rumbling calls made by elephants in Kenya. For each call, they knew which elephant made it and who that elephant was talking to. All of these rumbles got analyzed by a computer model that used machine learning.
PARDO: We trained this model to try and recognize patterns in the call that identified the receiver and then tested it on other calls that it hadn't been trained on.
GREENFIELDBOYCE: Now, you wouldn't expect every rumble to have a name, just like people don't use someone's name every time they talk to them. But what the researchers found is that almost a third of the time, their computer model could identify the correct elephant recipient of a call, suggesting some rumbles contained something that was effectively the name of the recipient.
PARDO: We can't say for certain this is how the names are encoded in the calls.
GREENFIELDBOYCE: Still, elephants seem to recognize it. The researchers know that because they did an experiment. They'd find an elephant alone and use a speaker to play back one of two rumbling calls, a call that was originally directed at that elephant or a call that was intended for someone else.
PARDO: We found that the elephants responded much more strongly on average to playbacks of calls that were originally addressed to them, relative to playbacks of calls from the same caller that were originally addressed to someone else.
GREENFIELDBOYCE: When the rumble was meant for them, they'd approach the loudspeaker and make response calls more quickly. These findings are all described in the journal Nature Ecology & Evolution. Karl Berg is at the University of Texas Rio Grande Valley. He wasn't part of the research team, but he studied the signature calls of wild parrots. He found the playback experiments in elephants convincing.
KARL BERG: Yeah, that really banged me over the head, you know, of - no doubt. I have no doubt that they're addressing them with these, you know, unique labels. Now are they nicknames? Are they names? Where did they come from? What are the acoustic attributes? You know, there's plenty of questions still.
GREENFIELDBOYCE: He notes that rumbles with identifying information often seem to come from mothers to their calves, suggesting that maybe elephants get names from their moms. Nell Greenfieldboyce, NPR News.
(SOUNDBITE OF HARRY STYLES SONG, "SUNFLOWER, VOL. 6 ")
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