How do fish know where a sound comes from? Scientists have an answer

Nick Petrić Howe

Welcome back to the Nature Podcast, this time: how light touches are sensed during sex…

Benjamin Thompson

…and working out how fish hear, directionally. I'm Benjamin Thompson.

Nick Petrić Howe

And I'm Nick Petrić Howe.

<music>

Nick Petrić Howe

How are the light touches and vibrations of sex perceived by the body? Despite the structures involved, known as Krause corpuscles being discovered more than 150 years ago, there’s a lot we don’t know about these sexual sensory organs.

Now, new research has done a detailed study of these corpuscles to understand how our sexual senses work. I caught up with one of the authors, Michael Iskols, to talk about what they found. And I started by asking him what researchers actually know about these Krause corpuscles.

Michael Iskols

So about 150 years ago, scientists discovered the structure of these nerves and humans and sheep and other animals, but we really didn't have a good understanding of their function and significance and sexual behaviour until now, we believe.

Nick Petrić Howe

And why do you think it is that we had such a poor understanding of them?

Michael Iskols

I think the first and maybe taken for granted answer is that these are in the genitals, and they're maybe a little bit awkward to study, but the other reason is that they're somewhat technically difficult to access.

Nick Petrić Howe

And so, in your study, you turn to mouse models. Would you just be able to lay out for us what it was that you set out to do in this study?

Michael Iskols

So, scientists have already established the structure of these sensory nerves. So, I think an important step was to better understand what they respond to and what their contribution is to sexual behaviour. And to do those experiments and record the activity of the neurons and ablate the neurons and activate them, you need genetic tools to do so, and fortunately, we have many of those available in mouse models.

Nick Petrić Howe

The paper, the way I read it, was sort of split into two bits. You sort of understood the form of these corpuscles and the function. So maybe let's start with the form. What was the structure like? What did you find here?

Michael Iskols

So we did, in fact, find that they're present in the genitals, the clitoris and the penis of the mice, but we found that they're pretty incredibly diverse, that some end in complex terminals, like balls of yarn, and others are far more simple and then kind of a straight terminal in the genitals. In the female it ends up being a little bit more complicated. But we found, somewhat surprisingly, that there's actually the same number of corpuscles in the clitoris and the penis, but because there's such a different size of the structures, that the density in the clitoris ends up being about 15 times higher than in the penis.

Nick Petrić Howe

And what do you think is the significance of that?

Michael Iskols

I think at that point in the study, we could really only speculate, and that's why doing physiological recordings, recording the sensitivity of these neurons, was really quite important. And we ended up finding that the neurons in the clitoris are actually more sensitive than the penis. And it's possible that the density can be a part of that.

Nick Petrić Howe

So I guess, yeah, let's move on to the sort of function of these corpuscles. You've mentioned a little bit of what you found there with the clitoris, that they're more sensitive, but overall, how did you find that these corpuscles work, and how this relates to, I guess, the sort of sexual function?

Michael Iskols

So by recording the activity of the neurons with different kinds of mechanical stimulation, we found that they're incredibly sensitive to light touch, and that includes vibratory stimuli about in the range of 50 to 60 Hertz. And as you mentioned, those in the clitoris are more sensitive than those in the penis.

Nick Petrić Howe

And you also look to see what happened if you activated these neurons in the mice, what did you find here?

Michael Iskols

Maybe not surprisingly, we found that with activation of the neurons that innervate the Krause corpuscles muscle in males, it led to an erection. But in females, we found that there was an increase in vaginal pressure with activation of the sensory nerves of the clitoris, and that could be either a direct reflex arc, or it could be an indirect recording of clitoris erection.

Nick Petrić Howe

And you know, you also then looked at the behaviour of mice that lacked these corpuscles. And as I understand it as well, there was a bit of a difference between the males and females here?

Michael Iskols

Right. So in the males that were lacking the Krause corpuscles and the neurons associated we saw that they were still interested in mating, they still mounted the females, and we think maybe that's because other senses are involved, like smell. But once they tried to insert the penis, they had some difficulty. They had trouble inserting the penis, and a few of them were unable to ejaculate. Whereas in the females they were far less interested in mating.

Nick Petrić Howe

And when you say that the male mice were sort of less able to ejaculate, they maybe had some trouble, do you think this is just because they lack the sort of sensory input?

Michael Iskols

We think that's a part of it. It seems like they were still able to control their bodies, they were still able to mount the female, but it seems like that difficulty really only came up when it came time to sense the ___location of the penis.

Nick Petrić Howe

And so these Krause corpuscles in the mice, they're very similar to the structure of human corpuscles. Do you think what you found here translates into humans?

Michael Iskols

So, I think it starts to build a foundation for some clinically relevant questions. I think it's interesting for neurobiologists, the function of the Krause corpuscles finally being discovered. But I think for everyone else, maybe the density discussion is interesting, but I think much of it finds the biological basis of something that they already knew, that the genitals are sensitive to vibration and that that's important for sexual function. So I'm excited to see how future studies maybe answer more clinically relevant questions like, how do the spinal cord circuits and brain circuits that the Krause corpuscles neurons contact go awry in states of sexual dysfunction, and how do these neurons develop and maybe degenerate across the lifespan?

Nick Petrić Howe

And to look at this from a slightly more business perspective, there is a huge multibillion dollar industry of making sex toys and things like that. Do you think that a better understanding of how these genital vibration sensing neurons work could help sort of develop even better sex toys?

Michael Iskols

I think this is an interesting situation where the industry actually beat us to it. They found the frequencies that the neurons are most sensitive to without even doing the studies, so I think we could actually learn from them.

Nick Petrić Howe

That was Michael Iskols from Harvard Medical School in the US. If that study has tickled your fancy, you can find a link to it in the show notes.

Benjamin Thompson

Coming up, new research that’s getting to the bottom of how fish know where a sound comes from. Right now, though, it’s time for the Research Highlights, with Dan Fox.

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Dan Fox

Something in space is emitting microwaves, and astronomers don't know what it is. The cosmic object – termed a millimetre ultra-broad line object, or MUBLO – was observed by analysing microwave radiation detected by an array of telescopes in Chile. The MUBLO seems to be compact, close to the Milky Way’s centre and rich in cold dust and fast-moving gas molecules. But its features don't match well with those of any known type of astronomical body. The researchers say the most plausible explanations are that it could be an intermediate-mass black hole, or a pair of merging stars obscured by dust, but the evidence fits neither explanation well. They add that more observations are needed to determine the MUBLOs identity. Learn more about this mystery by reading the paper in full in the Astrophysical Journal Letters.

<music>

Dan Fox

CRISPR gene editing can make rice plants more water-efficient and better at protecting themselves from sunlight – according to new research. Rice accounts for at least 20% of the world's calories, so genome edits that improved this staple crop could have wide benefits. Researchers used CRISPR to target a gene called PsbS that is involved in photosynthesis. However, instead of editing this gene directly, they edited a variety of DNA sequences that regulate PsbS activity, flipping some of the controlling DNA sequences backwards, which increased the amount of PsbS protein in cells. The modified rice plants made two to three times as much PsbS protein as normal plants, helping them to protect themselves from sunlight and use water more efficiently. Shed more light on that research by reading it in full in Science Advances.

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Benjamin Thompson

Next up on the show, I’ve been hearing about efforts to answer a long-standing animal behaviour question. To get the full effect, I’m gonna suggest you put your headphones on for this one…

<underwater bubble sounds>

Benjamin Thompson

How do fish know where a sound is coming from? It’s likely not a question you’ve ever asked, but it’s one of those things that has had researchers stumped for years. Fish have ears, they can hear sound, and evidence showed that in many cases they could figure out where it came from.

Johannes Veith

Early experiments were sometimes quite simple, where you, I don't know, hold a tuning fork to the tank wall, or drop something into the water, making sure that just the sound arrives. And then you could see, for example, that fish have a startle reflex, and that that startle reflex was directed away from sound. And so, people knew that fish can perform directionally hearing, even small fish, yeah, but the mechanisms puzzled researchers for decades.

Benjamin Thompson

This is Johannes Veith from Charité Berlin in Germany. He and his colleagues have got a paper out in Nature this week that explains what seems to be going on — for some fish at least. But before we get to what they found, let’s back up a bit and talk about why this has been such a tough nut to crack. You see, directional hearing in vertebrates that live on land has been well studied. Take humans for example. As a species, we’re really good at pinpointing where a sound is coming from. For most of us, sound is binaural — our two ears and our brain work together to get a sense of the source of sounds in our surroundings. And they do it in a clever way. Allow me to demonstrate:

Right now, if you’re listening in stereo, you should hear me somewhere just in front of your left shoulder. If I keep talking you should hear me pan around, before I end up over by your right shoulder.

So what’s going on? Well, it turns out there are two systems at play. The first is that sound arrives at your ears at different times. So if a sound comes from your left, it’ll arrive at your left ear before your right. The second is that your head creates an acoustic shadow — basically sound doesn’t travel through us as well as the air, so the sound is louder when it reaches your left ear compared to your right. Combining these two systems allows the brain to piece together where a noise came from. But land vertebrates like you or I ultimately evolved from a common fish ancestor. And this sort of hearing, well it doesn’t work underwater.

Johannes Veith

Like it's a completely different medium, and sound travels much faster, five times faster underwater than in air.

Benjamin Thompson

So for the fish, there is essentially no delay between the sound reaching each ear, because sound moves quickly underwater. But not only that, a fish's head doesn't really block sound to the same extent that a human's does.

Johannes Veith

Basically, the strength of the acoustic shadow is due to an acoustic impedance mismatch, and the fish is basically made out of a material that is very similar to water in terms of acoustic impedance. So it's very hard to cast an acoustic shadow underwater.

Benjamin Thompson

Because they’re mostly made of the same stuff, sound passes straight through fish. And their ears work in a different way to ours. Rather than detecting pressure waves, their ears detect another component of sound, called particle motion.

Johannes Veith

In the 70s, it got clear that fish can sense particle motion component of sound. It was just not clear how they can resolve a sound that is coming exactly from the one side, from the sound that is coming exactly from the opposite side.

Benjamin Thompson

When a sound is made underwater, it ripples through the molecules, knocking them together so they undulate back and forth. This motion affects the fish too, but inside their ears are tiny, calcium carbonate stones. These stones are denser than the water, and so don’t undulate as quickly. This difference in movement between the body and the earstones can be detected and translated into hearing. But there’s a problem with this. You can’t tell if the undulation began on the left or the right. Imagine you’re holding a balloon between two loudspeakers. If one of them plays a tone the balloon will wobble from side to side, but looking at this movement alone won’t tell you which side the sound is coming from.

All of which brings us back to the question “So how do they know where sound is coming from then?”. Well, there were a number of competing ideas, but in the mid-1970s there was one in particular idea proposing that fish could theoretically work out where a sound was coming from if they used information from both the particle motion and pressure. If we go back to our balloon analogy, particle motion is making it wobble, but it’s also getting squeezed and then expanding in response to the pressure wave created by the sound. If the sound is coming from the left, the particles will initially push the balloon right at the same time as the pressure wave compresses it. So essentially it shrinks a bit in the direction that the sound is travelling and you can tell where it’s come from. Crucially though, you need both, as particle motion or pressure alone won’t provide enough information.

So how might this work in the fish? Well, many of them have an organ called a ‘swim bladder’ — a gas-filled sack used for buoyancy — known to be pressure-sensitive and to play a role in hearing generally. There was evidence that this dual system was potentially at the core of directional hearing, but it’s something that’s been hard to test experimentally.

Johannes Veith

Once you go into a tank in a lab, you have massive reflections from the walls and reverberations that dominate the whole sound inside. And then imagine you want to control now pressure and particle motion, or you want to do experiments where you have a reliable stimulus coming from one direction, and you're basically in an echo chamber. It's going to be hard.

Benjamin Thompson

But this is something Johannes and his colleagues have overcome with a specially designed, and carefully calibrated setup.

Johannes Veith

We have a tank like 30 by 30 centimetres filled with water, and you put a little fish into like a centre part of the tank. So there's a tank in the tank system, and around this inner tank, we have loudspeakers all around, and we have a camera from top and infrared light from below, so we can track the fish and then trigger sound playback depending on the fish position.

Benjamin Thompson

And into this setup they put a little fish with a big voice…

<click sounds>

Johannes Veith

So they communicate with sounds, and the sounds are really loud.

Benjamin Thompson

This is the sound of the very chatty Danionella cerebrum.

Johannes Veith

It's a small fish that lives in Myanmar rivers, and it's the relative of the zebrafish, only like one centimetre large, and it is transparent, not just in a larval state, but also in adulthood. And in the context of this study, it also means we could look at the auditory organs and the hearing apparatus in vivo.

Benjamin Thompson

Using a microscope, the team could peer inside this transparent fish. They showed that its swim bladder was sensitive to the pressure part of sound, and this was passed via a set of bones to the fish’s ear. Additionally, the ears were sensitive to particle movement, adding evidence to the idea that both could be involved in directional hearing. But this wasn’t enough. The team needed behavioural experiments to prove it, which they did by playing a short, specific sound from different directions to fish swimming within their tank-in-a-tank.

<sound of object being dropped into water>

Johannes Veith

Yeah, we recorded it by dropping something into the water. We found that this sound works really well and better than other sounds.

Benjamin Thompson

The fish weren’t fans of this noise and in the majority of cases flinched away from it, very quickly.

Johannes Veith

It basically performs a very fast escape response initially it bends, like as a shape of a C, and then it escapes away. And then we basically track the fish, and then you can see, okay, and what direction does it escape?

Benjamin Thompson

The team’s fancy setup allowed them to decouple the two components of the sound by inverting the pressure part of the sound. This altered the relationship between the pressure waves and particle motion, which confused the fish.

Johannes Veith

We tested this prediction that when you selectively invert the pressure, you would create an acoustic illusion. So to say to the fish that the sound comes from the opposite side. And this is what we did, and this actually led to the fish not jumping away from the speaker but jumping towards it.

Benjamin Thompson

This result showed the tandem role pressure and particles play in helping a fish work out where a sound comes from. This fits with the hypothesis put forward in the 1970s by a scientist called Arie Schuijf that this is more-or-less how it works. For Catherine Carr from the University of Maryland, College Park in the US who’s written a News and Views article about the work, the results are compelling.

Catherine Carr

There are a whole array of theories about how fish can hear. The most popular has been Arie Schuijf’s theory, but there are many variations on it, and what this group did is they ticked through all the different theories, and they all had slightly different predictions and the Schuijf theory is the one that held up.

Benjamin Thompson

Catherine was impressed by the combination of techniques, equipment and use of the transparent Danionella cerebrum. But while the mechanism might be understood, what it’s doing in the fish’s brain remains to be figured out.

Catherine Carr

Because it's all very well and good to say that the fish must combine the measures of particle motion and pressure sensitivity, but that means that there should be channels conveying that information into the brain, and that the fish should be combining it.

Benjamin Thompson

What’s going on in the brain of this little fish is something that Johannes would like to know too, and he hopes that their transparent bodies will help with figuring that out. There are other questions that also remain to be answered. For example, what’s the role of this skill in the fish’s natural environment, and is this system seen in other fish? Although there are a huge number of species that have a swim bladder apparatus, there are also lots that don’t have a swim bladder at all – like sharks. They’ve got great hearing, but it’s currently unknown how they work out where a noise is coming from. But after decades of study, this new paper is shedding light on a question that on the face of it is pretty simple: “how do fish know where a sound is coming from?” While there’s clearly much still to learn, Catherine thinks the results could help us design equipment to make more sense of the world beneath the waves.

<bubble sounds>

Catherine Carr

I'm a scuba diver myself, and I must tell you, it's very hard when you're underwater for us to tell where the sound is coming from. This is how you would build a simple apparatus. You need a directional detector for particle motion, and then you need an underwater bubble to vibrate in the sound field. And those two things together will give you accurate information about the direction of the sound source. And I can think of many reasons why people would like that, any kind of search and rescue, any kind of operations where you need to identify some energy source.

Benjamin Thompson

Catherine Carr there. You also heard from Johannes Veith. To read Catherine’s News and Views article, and Johannes’ research paper, head over to the show notes for a link.

Nick Petrić Howe

Finally on the show, it’s time for the Briefing Chat, where we discuss a couple of articles that have been featured in the Nature Briefing. Ben, what have you got for us this time?

Benjamin Thompson

Well, this week, we're heading over to the ruins of the Maya metropolis Chichén Itzá, which is in what's now Mexico. And it's a story of how ancient DNA from the ruins is telling the story of ritual human sacrifice. Now, we are going to be talking about child sacrifice here. So if that's something you don't really want to hear about, skip forward a few minutes to the next story. And this was a story that I did read about in Nature.

Nick Petrić Howe

So how is it the DNA is telling us more about these ritual sacrifices? I would think it would be more archaeology, sort of the ruins and that sort of thing that would tell us.

Benjamin Thompson

Yeah, that's a good question, and it is a mix of the two. But ancient DNA is revealing so much more about, you know, human relatives and ancestors than I think we've ever known before. But in this case, we're looking at one of the largest Maya cities, right? And it's very important between about 800 and 1000 ad. And there is a bunch of evidence of ritual sacrifices in this site, right in engravings on the buildings and things like that. But also the remains of hundreds of victims were recovered from a 60-metre sinkhole known as the ‘Sacred Cenote’. And so I think archaeologists and scientists knew a lot about what was going on from remains found in this area, but now say ancient DNA from some of the city's youngest victims adds to the story. And this is a study in Nature, and it's actually looking at some remains that were found in an underground chamber and an ancient cave that was actually in a different ___location in the site, and this was part of a shrine, sadly now destroyed by construction. But DNA analysis of some of the skeletons uncovered here has led to, well, some surprises it has to be said.

Nick Petrić Howe

Well, don't keep me in suspense then. You said that these were from very young people. What other surprises were there from this DNA evidence?

Benjamin Thompson

Well, the biggest surprise is that they were all boys. Okay, now, the team behind the work obtained this ancient DNA from 64 of roughly 106 individuals buried at this underground site. And so yeah, all boys, and a surprising number were close relatives as well. So, carbon dating suggests that they were sacrificed between the 7th and 12th century, and a quarter of them had a first or a second degree relative, right? So, a sibling or a cousin. And in fact, there was two pairs of identical twins as well, which is unusual in terms of, you know, the number of twins that are born into a population, and their presence could be linked to rituals involving twin figures from Mayan mythology – according to researchers. And this finding did come as quite a shock, apparently. And it's different to the remains in the sinkhole site, the Sacred Cenote, which had individuals that were boys and girls. And this finding is a world away from the, you know, outdated view that sacrifices really involved young women and girls.

Nick Petrić Howe

So what do researchers believe the significance is? That it seemed to be that they were very closely related a lot of the time, and they were all boys.

Benjamin Thompson

Well, there is this mythology aspect, but it's not fully clear why these children were selected. But some more analysis has been done, and it suggests that they, you know, had a plant heavy diet of maize, corn, I suppose, which is typical of ancient Maya. But the related individuals tended to have similar diets, suggesting they were raised in a similar way. And there's a quote in this article that says that “probably this was part of preparing them for this sacrifice”, and that “death and sacrifice for them means something completely different to what it means to us. For them, it was a big honour to be part of this”. So a bunch of new knowledge has been uncovered from this research.

Nick Petrić Howe

So I guess, like this ancient DNA evidence is really giving us a better understanding of what's going on there. Do the researchers expect any more surprises in the future?

Benjamin Thompson

Well, there may well be some more, actually, it turns out. So the remains of these children who were studied for this work are from the same genetic population as present day Maya people who live in a village near Chichén Itzá, and there's been some comparison of the genomes of these two groups. And what's interesting is– is these ancient genomes are the first from Maya people that predate the arrival of Europeans, and they offer some clues as to the effects of how Colonial Era epidemics may have affected indigenous Mexicans. And what researchers have found is that versions of genes involved in recognising pathogens more common in modern Maya, and one that's become twice as common in the modern Maya, is linked to protection against the severe Salmonella infection. Right now, other research suggested that Salmonella enterica Paratyphi, right, this bacterial pathogen was involved or linked to a 16th century epidemic that killed millions of people in Mexico and beyond. And so it could be then that this analysis of these modern genomes has shown that there is this natural selection that has taken place between now and then. But this is somewhat contested, and other researchers suggest that there could be other factors at play which would explain this difference. But I think overall, what it does teach us is a lot more about Mayan culture and ritual sacrifice seems to have been a regular event in Chichén Itzá, but there are lots of aspects about it that really remain unclear, but maybe are a little bit more understood thanks to this work.

Nick Petrić Howe

No, it certainly seems to add to, like this growing library of evidence that we're getting from ancient DNA. And as we get better at collecting DNA that's, you know, from a long, long time ago, hopefully we'll learn even more about these ancient cultures. For my story this week, it seems that we're doing a bit of an animal special, because I have another animal story on the podcast. And this is some research that was reading about in Nature that suggests that elephants might have names for one another.

Benjamin Thompson

Right? So, yeah, of course, we've heard about fish hearing. Now we're talking about elephant talking. And we know that elephant communication exists, but I guess nobody really has a hand on exactly what these animals are talking about, how they're communicating, but this work suggests that each of them has their own name that they use when they're talking to others. Is that right?

Nick Petrić Howe

Yeah, that's right. I mean, I guess it depends how you define talking, but it certainly seems that there are some vocalisations, some sort of grunts that they use, that seem to be when they want to address a particular elephant. So, we tend to think of this as just being a human thing. I call you Ben. You respond to that. You call me Nick. I respond to that. But there is evidence that other animals have sort of things like this. So, in bottlenose dolphins and orange fronted parakeets, they are known to identify each other by mimicking the signature calls of those that they're addressing. So, a certain dolphin will have a particular call that they use, and another dolphin will use the same call to address it, which is not quite what we do. But in this case, the elephants seem to be doing something very similar to what we do, insofar as they have a particular sound, like the sound Ben, that they use to refer to a different elephant.

Benjamin Thompson

So, a specific unit of sound, then, that represents an individual. That's really something.

Nick Petrić Howe

It is really something. And this is decades of research to get to this point. So, between 1986 and 2022, this team of researchers recorded the sort of deep rumbles the female African elephants do to one another. And then they've used machine learning to scour through that and identify which ones are when an elephant is being addressed, and the machine was pretty okay at that. It correctly identified when an elephant was being addressed based on these rumbles 27% of the time, which may not sound like a lot, but it was much more than random. And then they actually took this a little bit further, and they played what the machine learning had identified to the elephants to see how they'll respond. And what I'll do for you is I'll play one of the sounds, so you have an idea of it.

<elephant grumbling sounds>

Nick Petrić Howe

So that sound you heard there was a call being played to what we call Margaret, an elephant called Margaret, addressing her, and the second sound was her actually responding to that. So what the researchers did is they played several of these sounds that they'd found that were referring to specific elephants, and they saw how they responded. And when they played the sound, the elephants would look and then they would approach the thing, and they would respond, they would make calls. So it seemed very much like they were responding to their name.

Benjamin Thompson

Wow. I mean, that's kind of cool. I mean, I guess, you know, humans talking to animals, conversing with animals is, is one of those things that's been written about, you know, for hundreds and hundreds of years. And I think we've covered on the show before about, you know, using AI to find the kind of hidden things, hidden to humans, I suppose, within animal sounds and this is another one. I mean, what are the chances that it's just saying something random? It's just interested in an elephant like noise.

Nick Petrić Howe

Well, that's a good question. And there is more work to be done here. We need to do some more studies to really confirm whether the elephants are actually calling each other by name, if you want to say it like that. But it does seem that the elephants were at least responding specifically to these calls, because if you played, let's say a different elephant's name to an elephant, they wouldn't respond in the same way. So they would get a much greater response if you played like the elephant's like, actual, you know, quote, unquote name. So it does seem that there's something there, but, yeah, absolutely, more research to be done.

Benjamin Thompson

I'm fascinated. I'd love to know what that actually– what those names actually mean in elephant-ese, if that's the right phrase. I wonder what Margaret actually translates to in elephants.

Nick Petrić Howe

Well, exactly. And also it opens up the possibility that they can maybe put some sort of meaning into things. Are they able to talk about places? Do they have names for places that they go to? And that sort of thing like, there could be a whole world of elephant communication that we don't understand. We know it's very complex. We know that elephants have very strong social bonds. We know they have got a great memory as well. So maybe there is a lot that's going on here that we just don't understand and maybe some of these AI tools could help us uncover that. And also this could be quite useful for conservation as well. You can't just put a bunch of elephants together and be like, ‘Go, be conserved,’ because they have these really complex social relationships and things. So by understanding this and how they sort of interact with one another. It could really help us conserve these elephants, because these animals are still endangered. So anything that we can use to sort of help us conserve them would be really great.

Benjamin Thompson

100% I mean, I'm fascinated by this, I say secret world of animal communication. Secret to us because so much of our sort of tunnel vision is through the kind of humanlike senses that we have. And I'm sure there are many, many more of these things just waiting to be discovered. But let's leave it there for this week's Briefing chat. And listeners, head over to the show notes, where you can find links to those two stories and where you can sign up for the Nature Briefing to get more like them delivered directly to your inbox.

Nick Petrić Howe

That's all for this week. Don't forget, if you like what we do, leave us a review wherever you get your podcasts.

Benjamin Thompson

In the meantime, if you want to reach out to us, we're on X @NaturePodcast, or you can send an email to [email protected] I'm Benjamin Thompson.

Nick Petrić Howe

And I'm Nick Petrić Howe. Thanks for listening.