transcript

Speaker 1:
[00:03] Hey, it's Flora Lichtman and you're listening to Science Friday. Investigating an iconic animal sound. The dolphin whistle. But what exactly is that dolphin saying? My next guest is trying to find out. She's an expert in dolphin communication and has been compiling a database of whistles from a pod of dolphins in Sarasota, Florida that's been studied since the 1970s. And she's working to answer some fundamental questions about dolphin dialects. Dr. Laela Sayigh is a Senior Research Specialist at Woods Hole Oceanographic Institution. Laela, thank you for being here.

Speaker 2:
[00:43] You're welcome. Thank you for having me.

Speaker 1:
[00:45] Let's do some dolphin whistle 101. So every dolphin has something called a signature whistle. Let's listen to some examples first. Okay, so what is a signature whistle?

Speaker 2:
[01:04] Yeah, well, signature whistles are the closest thing to human names that we know of in the animal world. They really are a lot like our own names. So each dolphin has their own. They do make their own signature whistles a fair bit, which is sort of different than how we use our own names because we can usually see each other, but they use them maybe when they're out, you know, sort of in places where they can't see each other and use them to keep in touch.

Speaker 1:
[01:34] They're like, Flora here, something like that.

Speaker 2:
[01:36] Yes, yes, that's right. That's right. Well, they'll kind of call out, I'm here, I'm here. But they do also copy each other, and they will copy another dolphin's signature whistle as a way of calling out to them, which is more in line with how we use our names.

Speaker 1:
[01:50] Do they name themselves? Like, how does a signature whistle come to be?

Speaker 2:
[01:54] Oh, that's kind of the $60 million question or whatever. It was actually the focus of my PhD dissertation a long time ago, and I still cannot give you an answer. I wish I could. It's something I would love to know the answer to. We know they do learn their sounds, so they learn to produce their whistles, and that's a really cool thing in and of itself because a lot of animals don't learn, but obviously we do, and so that's something that's really important to us. We know in Sarasota, the population that I study, that about a third of the calves end up developing whistles that are pretty similar to their moms. I was actually just looking at one yesterday that was literally identical to his mom, although that's not very common at all. In fact, more common is for them to not develop whistles like their moms, and we have no idea why some do and some don't. Anyway, questions that I would love to know the answers to.

Speaker 1:
[02:54] Are they unique? Does every dolphin have a different signature whistle or half of them named Jane?

Speaker 2:
[03:01] That's a great question too. Well, for the most part, they are unique. Usually, at the very least, there's some subtle difference that we can use to differentiate one animal from another. It might end up going an upsweep versus a down, something like that, even if the rest of it looks the same. Although occasionally, we do run into these very unusual situations like the calf that I was just mentioning that really developed a whistle that is so similar to his mom that we can't distinguish it. At least we can't. It's possible that there are some features that enable them to, but usually the distinctions are pretty visible to us. We can see really big differences among the whistles for the most part.

Speaker 1:
[03:44] Do they ID themselves the same way to their friends as they do to their families? Do they have different signature whistles for themselves in different scenarios?

Speaker 2:
[03:52] We have not seen evidence for that, although I wouldn't say that we have really looked specifically for that. They do vary aspects of their whistles in ways that make actually classifying their whistles a bit complicated. I guess other than one exception there, which I might just mention, we did look at the signature whistles of the adult females when they were communicating with their calves versus not with their calves, with other animals. And in that study, we did find that they tended to increase the maximum frequency of their whistles when they were communicating with their calves. And that was something that we liken to human motherese, which was when we speak with infants and small children, and we speak in a more kind of sing-songy type high-pitched voice.

Speaker 1:
[04:41] Like, oop-doop-doop-doop, you're so cute.

Speaker 2:
[04:43] Exactly. Yep, yep. So, I mean, we don't know if it's really functioning in a similar way, in any way, shape or form with dolphins. But it was pretty cool to find something that was similar in that way.

Speaker 1:
[04:56] We have a recording that you took of a mother and her calf. Let's listen to it.

Speaker 2:
[05:07] So, those were slowed down.

Speaker 1:
[05:09] They were slowed down. Okay. I was wondering because I was like, this is actually, this sounds a lot like me begging my kids to get their shoes on. But that makes sense. It's slowed down.

Speaker 2:
[05:18] Yes. Those are slowed down to be able to tell the difference. So, the second one was the one when she was with her calf. The first one was when she was not with her calf. And so, hopefully, people could tell that the second one went up higher at the end.

Speaker 1:
[05:31] Let's listen again. Let's listen again.... Definitely. So, yeah.

Speaker 2:
[05:43] Yeah. And I did slow those down. Because otherwise, it's actually pretty hard to tell at regular speed. Our ears are not really that well tuned in to those frequencies.

Speaker 1:
[05:53] Do we know why mothers change their whistles around their babies?

Speaker 2:
[05:56] No, we do not know. You know, we have theories about it, but that's all they are. And we really are not sure that we'll be able to answer that question either, to be honest. Because it's pretty hard to really test hypotheses about why they might be doing that.

Speaker 1:
[06:15] Is it hard to capture these sounds?

Speaker 2:
[06:18] Not to capture the sounds themselves. Although, well, I guess I should backtrack on that. It is hard to actually capture the sounds and be sure which dolphin is making them. That's actually been one of the things that has been really one of the biggest challenges, I would say, in the study of dolphin communication over the decades that I've been involved. For the most part, we can't actually even see them anyway, because they're underwater. But even if we can see them, they don't make any movement when they vocalize. So they don't open their mouths like we do, for example. Their sounds are made in a really different way. But we do have this capability in Sarasota, where we can temporarily handle the animals, these brief catch and release health assessments that are carried out down there. And in that context, we can record them with contact hydrophones that we can put actually with suction cups right on their bodies, and also with these digital acoustic tags that also attach with suction cups that we can put on before we release them. And so, those are ways that we can get some really nice recordings of known dolphins, which is pretty important when you want to understand their communication.

Speaker 1:
[07:32] Well, how do you know that what they're saying is what you think they're saying?

Speaker 2:
[07:36] Well, I'm not even sure I think of anything about what they're saying. I mean, I don't...

Speaker 1:
[07:42] Well, even the signature whistles, like if I were a dolphin and a human being were attaching a microphone to my head with a suction cup, I don't know that I'd be like, Flora, Flora, Flora, Flora.

Speaker 2:
[07:50] So true. And that's a great question too. And we have been able to confirm that in a bunch of ways. So for one, the situation when dolphins are isolated, at least even temporarily or even just by a few feet from another dolphin or from whoever they're with, that is a context that really promotes signature whistle production. So they tend to just make a lot of signature whistles when they're in that situation of being isolated, even very briefly and even still an earshot of other dolphins. And this was something that's been observed initially in captivity by the people who discovered signature whistles, David Melba Caldwell, and they recorded isolated animals back then and found that they made almost 100 percent just one specific whistle. And then that's how they coined them, the signature whistles because they were unique for each individual. And we do find in these health assessment context, not 100 percent, but we see maybe about 85 percent of any particular dolphin will typically be one's whistle type. And so that's how we are able to call that the signature. But then we also can confirm that by studying those same dolphins when they're just out swimming around doing their own thing. And we observe those same whistles. So we know that they're not just making some kind of, you know, different type of call when they're in that health assessment context. They are making their signatures.

Speaker 1:
[09:21] I mean, graduating from 101, if I were taking intermediate dolphin whistle, are there other types of whistles that you've identified?

Speaker 2:
[09:29] Yes, there are. So there's, as I already mentioned, signature whistle copies, which are pretty cool. And, you know, again, more like how we use our names. But then there are also a whole bunch of other types of whistles that we call non-signature whistles, which I wish had a different name, because it's kind of a lame name for them. But we'll be happy to take suggestions from people of other things we could call them. But for now, that's what they're called. And we have really only just started really studying these whistles in RNS. For many years, we kind of thought they were just sort of random. We were pretty focused on the signature whistles and we would see these other whistles and be like, okay, those are, in fact, they used to be called variant whistles, which sort of implied that there was just something weird about them or whatever. But we stopped calling them variant whistles. They're now just called non-signature whistles. And we now know that there is not something weird about them. There's a lot of really cool things about them. They make a lot of shared non-signatures. So I've now discovered quite a few non-signature whistle types that we've seen made by multiple dolphins.

Speaker 1:
[10:37] Wow.

Speaker 2:
[10:38] And so we're trying to do some playback experiments now to understand how those non-signature whistles function.

Speaker 1:
[10:44] We have an example of one. Let's hear it. One more time.

Speaker 2:
[10:51] Yeah. That one had a, you can tell, like a sort of a flat component at the end that is very striking and very unusual in dolphin whistles. So that was one of the first ones that I discovered. It really stood out to me because it was so different sounding from what their signature whistles usually sound like.

Speaker 1:
[11:11] Do all of these sounds constitute a language?

Speaker 2:
[11:14] I don't use the term language when talking about their communication. I mean, just because it's so tied with our own language. I mean, that's how we use the term. Our own language has a lot of features that, how we define our language syntax and things like that. So I guess I don't necessarily think it's that useful to try to find human language features in their communication. I guess I would be surprised if they were there to any great extent because we have been distinct from them evolutionarily for more than 50 million years.

Speaker 1:
[11:56] I mean, it is a form of communication with shared sound.

Speaker 2:
[12:01] For sure.

Speaker 1:
[12:02] Maybe it's not our language, but it seems like some kind of communication. Maybe we don't have the right word, but it doesn't seem that different.

Speaker 2:
[12:09] Absolutely, communication. No doubt communication. That's what I like to call it. Rather than language, they are communicating with each other.

Speaker 1:
[12:19] This seems like a dream job. I saw pictures of you in the water with dolphins. Are they, I have to know, are they as adorable as they seem or is there a dark side?

Speaker 2:
[12:29] Well, I won't lie, they are definitely cute to look at. I mean, I worry that people think that dolphins might just be these kind of cuddly, nice creatures. You know, it might be an inclined to like jump in the water with them or something, which I would not advise, you know. Really? No, definitely not. They're powerful animals. They could do harm if they wanted to. And I know a colleague of mine said, you know, would you jump on the back of a lion? I don't think so, you know. But people don't think of dolphins that way.

Speaker 1:
[13:03] Once again, social media is misleading us.

Speaker 2:
[13:06] Mm-hmm. I think that's very true. And probably the TV show Flipper might have had something to do with it, too.

Speaker 1:
[13:16] Dr. Laela Sayigh is a Senior Research Specialist at Woods Hole Oceanographic Institution. Laela, thank you for being here with us.

Speaker 2:
[13:22] You're very welcome. Thank you for having me.

Speaker 1:
[13:25] This episode was produced by Shoshana Buxbaum. Before we go, Earth Day is coming up next week, and we want to hear about the places on our planet that you love and feel most connected to. Maybe it's the pond where you learn to swim, or your grandmother's vegetable garden, or that park where you do all your processing. Call us and tell us about your happy place. Take us there. What does it look like? What does it smell like? What does it sound like? And why is it so important to you? 877-4-SciFri is our number. That's 877-4-SciFri. I'm Flora Lichtman. Thank you for listening. Science Friday brings the joy of discovery to millions of curious listeners every week. When you sponsor Science Friday, you connect with a dedicated audience that values knowledge, exploration, and learning. These are folks who love getting into the details, who actively engage with ideas, and who value trustworthy information. Learn more at sponsorship.wnyc.org.