SCOTT DETROW, HOST:
All right, think for a second about a lion's roar. You've heard this sound, I'm sure.
(SOUNDBITE OF LION ROARING)
DETROW: Or some version of that sound. This particular roar comes courtesy of a lion named Jeronimo (ph). Well, what if I told you that this sound...
(SOUNDBITE OF LION ROARING)
DETROW: ...Was also a roar? It is actually a new type of roar altogether, one discovered by researchers at the University of Exeter with the help of AI. They say their findings, which were published this month in the journal Ecology And Evolution, could help in lion conservation efforts. Lead author Jonathan Growcott joins me now to talk about roars. Welcome to the show.
JONATHAN GROWCOTT: Thank you very much.
DETROW: Let's start with this. Tell me about this new roar, what it sounds like, why it's different.
GROWCOTT: Yeah, so it's really interesting. So I think everybody potentially knows of a lion's roar. They've heard it through so much different media. But what you may not know is that lions roar in what's recorded as a roaring bout. They actually start off with a series of soft moans that develop into these roars.
(SOUNDBITE OF LION MOANING)
GROWCOTT: And then the vocalization subsides with a series of grunts.
(SOUNDBITE OF LION GRUNTING)
GROWCOTT: The specific part of this roar, which is called a full-throated roar, has recently been shown to be an individually unique signature for lions, a bit like human fingerprints, so you can identify lions by this specific type of roar.
DETROW: Everybody has a different roar. We heard Jeronimo's. Others are slightly different?
GROWCOTT: Exactly, but it's specifically this full-throated roar. And previously, selecting this roar out of all of the other vocalizations within the roaring bout has been challenging because of this - as we've discovered - this second intermediary row.
DETROW: What makes a roar a roar? Like, why does this matter, and what's the difference between a (imitating lion roar)-like roar and another noise that a lion would make?
GROWCOTT: So the full throated-roar is the loudest, most complex part of the lion's roaring bout. It starts at a low pitch, it rises to a high pitch and then drops down again to a low pitch, almost like if you imagine someone really yawning, really stretching and yawning. The intermediary raw, on the other hand, is a flatter vocalization. There is less variation in pitch.
From a monitoring perspective, we could use these full-throated roars, potentially, as a conservation tool. If we can tell which lion is Jeronimo and which lion is potentially Perseus or Steve or Sandra, then we can start to count the number of individuals in a landscape. And if we can count these individuals, we can derive population estimates, which is a really crucial conservation metric. You can then turn understanding of population trends into conservation hotspots where you can target certain places with on-the-ground conservation activities.
DETROW: So we said earlier that AI was able to identify this new type of roar that, I guess, human researchers hadn't fully realized was a roar before. How exactly did that work? What was AI picking up on that trained expert ears had not picked up on?
GROWCOTT: So as we heard before, the difference between these two roars is quite marginal. And even for expert ears, it was really challenging to understand these differences and to even notice that there were differences. I can detect them, but I've listened to thousands and thousands of roars. And so what we wanted the AI model to be able to do was pick out these specific metrics within these roars, so maximum frequency and duration, which are really challenging for humans to hear, but the AI can use that to predict which types of roars are which. And what we found was that the full-throated roars the AI model predicted, this bespoke AI model that we built, actually did a better job at then differentiating between the different individuals down the line.
DETROW: You spend a lot of time thinking about and studying lions. What's your favorite aspect of lions?
GROWCOTT: Oh, I mean, you've got to respect how much they sleep.
DETROW: (Laughter).
GROWCOTT: Any animal that spends 20 hours a day doing basically nothing has got to be respected there, I think. I still remember the very first time I saw a lion, which was on a night drive, and there was this sole lioness that was just skulking through the undergrowth, and I was just captivated. So I think there's just something so brilliant about an animal that is so secretive by nature but is also just so iconic.
DETROW: That is Jonathan Growcott, Ph.D. student and researcher at the University of Exeter. Thank you for talking lion roars with us.
GROWCOTT: Thank you very much for having me on. Transcript provided by NPR, Copyright NPR.
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