Award-winning journalist Amy Martin has spent years tuning into nature’s hidden soundtrack. As the host and creator of Threshold, she explores the intricate ways life communicates beyond human perception. In its latest season, Hark, Amy uncovers how species from birds to dolphins—and even turtles—use sound to share information we’re only beginning to understand. Thanks to breakthroughs in acoustic research, these conversations are finally coming into focus.
Award-winning journalist Amy Martin has spent years tuning into nature’s hidden soundtrack. As the host and creator of Threshold, she explores the intricate ways life communicates beyond human perception. In its latest season, Hark, Amy uncovers how species from birds to dolphins—and even turtles—use sound to share information we’re only beginning to understand. Thanks to breakthroughs in acoustic research, these conversations are finally coming into focus.
Scientists mentioned: Mike Parsons, Rex Cocroft, and Gabriel Jorgewich Cohen
Photo credit: Nick Mott and Jed Allen
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Shelby Stanger:
Every time we step outside, there's a cacophony of noise. If you're in the city, you'll probably hear cars, sirens, and dogs barking. When you're out in nature, the soundtrack softens, but there's still plenty to hear if you tune in. A chorus of bird song or the chittering of squirrels. Beneath these layers of noise is an abundance of sounds that humans can't detect, from ants marching toward their colony to the creaking of new growth on a plant.
Amy Martin:
Think about a flower. You have this beautiful, bright thing trying to attract pollinators. That flower is also an ear, and it is listening for the pollinators in some cases. So certain kinds of flowers, when a bee is buzzing closer, they start to sweeten up the nectar that they produce so that when that bee lands and takes a sip of their nectar, they're going to hang out longer and they're going to come back and they're going to tell their bee buddies like, "Hey, over here, this is a really good flower."
Shelby Stanger:
Award-winning journalist Amy Martin is obsessed with nature's soundtrack. She's the host and creator of the environmental documentary podcast, Threshold. In the latest season, titled Hark, Amy discovered that it isn't just flowers who are listening. All sorts of species like birds, dolphins, and turtles communicate using sounds that humans often can't hear, much less decipher. But with advances in acoustic research, we're getting closer and closer to understanding what it all means. I'm Shelby Stanger, and this is Wild Ideas Worth Living, an REI Co-op Studios production presented by Capital One and the REI Co-op Mastercard.
Amy Martin, welcome to Wild Ideas Worth Living. I love that you're in Missoula half the time and then Sweden.
Amy Martin:
Yeah. Yeah. Thank you for having me on. I'm excited to be here. And yeah, I have ended up in this weird life that I would never have expected where I move back and forth between Northern Sweden and Western Montana.
Shelby Stanger:
Why? How? This is amazing.
Amy Martin:
Well, I was in Sweden for season two of my podcast, Threshold, and I met a guy and fell in love and now he's my partner.
Shelby Stanger:
We love a good adventure love story.
Amy Martin:
They go together, right?
Shelby Stanger:
So you're a podcast producer and host. How did you get into this field of work?
Amy Martin:
I had done radio in colle ge. I'd worked at an NPR affiliate as a student reporter and just loved telling stories and sound. I had this whole post-college life as an independent musician. And then I just really got pulled back into journalism, and so I started Threshold. And every season, we just take a brand new topic and go as deep and big and wild as we can. And much like your show, we're really focused on getting out into the world.
Shelby Stanger:
And so how did you do it? Did you pitch sponsors? Did you just start it? Did you bankroll it yourself?
Amy Martin:
I just started it and bankrolled by having almost no expenses and using my credit card and having other jobs and scrapping. And yeah, so we now have a little nonprofit organization and we're just completely listener-funded and we're rolling. Who knows how long it'll last, but so far we've got five seasons out and we've got a sixth one in the works.
Shelby Stanger:
It's so badass. And if you're wondering why I'm digging in so much to your backstory, it's because, I mean, everybody here who listens is interested in nature and adventure and has some sort of wild idea. And a lot of us are afraid to do it because of money or fear. And I think what's also interesting, and I'm sorry I'm going on a tangent, but the path to your wild idea is not always linear, but somehow you've blended your background as a musician and then your background as a journalist and then working for public radio. And this season, Hark, seems to be the perfect fit for all these things that you're passionate about and have skills at in your life. It kind of just looks like this perfect Venn diagram. Everything is all unifying in the middle circle. So let's talk about this season, Hark.
Amy Martin:
Yeah. Well, first of all, thank you for reflecting that back to me, because I hadn't really thought of it that way, but when you just, I'm like, oh yeah, this is all... Maybe it isn't just like a scattershot Jackson Pollock painting. Maybe it flows together. I will say that there's something about, So this season, Hark, is all about putting the non-human voices behind the microphone. And even before I had ever conceived of Threshold before I was doing podcasting, I wanted to make something like this. So it's maybe not surprising that this is our longest season yet, the 16 episodes. It's kind of a behemoth of a season, but I think it's partly because in some level it's been brewing in me for just so long. And also because the world is so fascinating. There are so many beautiful, weird, funny, surprising, emotionally startling and heart-opening voices out there. And you start listening to them and I'm like, "Well, I want to listen to everything. I want all the critters to be in this season." So it was actually really hard to just put it into 16 episodes.
Shelby Stanger:
Amy and her team travel around the world to talk to researchers, professors, and other experts about the sounds of nature. Each episode of this season walks through the evolution of life, starting with microbes, then fish, and moving on to birds, plants, elephants, dolphins, and more. It turns out there's an entire field dedicated to studying the sound of living things. It's called bioacoustics. For Amy, discovering bioacoustics opened up a new way of experiencing the natural world, and it became the foundation for this season of her podcast.
First of all, can you define bioacoustics for everyone?
Amy Martin:
Yeah. So bioacoustics is essentially just listening to life. Bio being life, acoustics being sound. That's the simplest kind of broadest way of thinking about it. Some people also call it acoustic ecology, gosh, they're eco-acoustics, but it's basically using sound to understand another form of life or a place. One of the really cool things in Australia was this thing called the Australian Acoustic Observatory where they have, I think it's 300 some listening stations set up in wild places all across that gorgeous, crazy, cool country. And they're just going to have all this data to try to understand the place as a whole, the birds and the bugs and the changes in the weather and how much people are interacting and all these different things.
So that can be bioacoustics, listening to a whole place, or it can be somebody who's like, "I want to decode dolphin communication." Or I talked to a woman whose focus is naked mole rats, which super weird little underground rodents and they have these beautiful bird-leg voices and they're talking all the time. Why? What are they saying? It's just like everywhere we listen, there's a new mystery to discover.
Shelby Stanger:
Okay. I want to hear all about which critters are in this season because in the trailer, there's like sea otters, there's whales clicking, there's dolphins talking. I mean, I want to know exactly what the dolphins are saying when I'm out surfing.
Amy Martin:
Yeah. Did you hear them a lot?
Shelby Stanger:
I just went out this morning right before our little conversation and almost didn't make it on time because yeah, I was so inspired by your trailer that I had to go out and see if I heard dolphins. I mean, I see them all the time. I didn't see them this morning. I stepped on a fish though. It was exciting. I wanted to know what it thought when I stepped on it. It squirmed underneath me and I was just really happy it wasn't a stingray, but I digress. Okay. So what critters are in this season? Give me a couple of examples.
Amy Martin:
Well, fish actually, that's the whole second episode, and they talk and they sing and they make choruses. And I didn't grow up near the ocean, so maybe everybody else knows this, but I was completely shocked. I'm like, oh my gosh, fish have so many sounds. Sound is really, really important to them, as it is for almost anything that lives in the water because it's really hard to see underwater, but sound travels, I think it's four times as fast in water as it does in air and it persists for much longer. So yeah, some groups of fish in the deep ocean come together, thousands of fish, and make these choruses that are louder than rock concerts. They're just belting it out together.
Shelby Stanger:
Can we listen to those fish?
Amy Martin:
Yes, we can.
Shelby Stanger:
How do you capture the sounds of deep water fish? Like you just take a microphone and shove it? I mean, I've taken GoPros underwater, but what are you taking down there?
Amy Martin:
Well, the scientists who are really doing this work, there's a couple of different ways that they're capturing fish sounds, but they all are based around hydrophones, which is just a fancy word for a microphone that you can put into the water, but they're increasingly these super cool underwater listening stations that are permanent, where they put them on the sea floor, obviously not in the deep, deep, deep, but try to position them in places that are away from shipping lanes and things. And you can, with the advances in technology and the ability to record for long, long periods of time in the data capacity that we have now, they can just leave them running all night, all day for months. And they're discovering all kinds of things like these fish courses. People knew there were fish courses, but only in like the last 10 years are we understanding they're happening way more than we thought, way more kinds of species.
In a lot of cases, they're still trying to figure out like, why? Why are they doing this? Are they doing it just, is it like mating? Is it territory? Are they just having a party? There's so many things we don't know about what's happening in the ocean.
Shelby Stanger:
So what did you learn about the fish?
Amy Martin:
Let's see. I'm trying to think of one of the fun little tidbits I learned. Kind of like wolves or coyotes, some fish also seem to chorus more in relation to the moon because of course the light of the moon affects them when they're in the ocean as well. I can't say why. I don't think we necessarily know why, but just the fact of that is completely delightful to me to just think that like somewhere in Montana, there's a coyote and her pups howling at the same time that in like deep in the Pacific, there's some fish that are making these crazy noises all together.
There are also some thoughts that maybe they are making these sounds together in part to kind of confuse predators. Like if they're all making a sound loudly all at the same time, it's kind of like dizzying and disorienting for things that want to eat them, but it really ends up becoming very specific of like this species in this place, and there's a huge amount that's unknown about it. So mysteries await.
Shelby Stanger:
For the most recent season of her podcast, Threshold, audio journalist Amy Martin investigated the sound of non-human voices on our planet. It took her team two years to make the 16-episode season titled Hark. Amy traveled to Australia, Kenya, Europe, and she even did some reporting in her home state of Montana. Along the way, she met some fascinating experts who are changing how we think about the noises that plants and animals make and why they make them.
So what was the most fascinating thing you uncovered while making this whole show? Was there anything that just completely surprised you?
Amy Martin:
Oh, so many things. Plants can hear, and they are actually using what they hear to help shape their lives. And it feels like dangerous ground because it feels like it can very quickly stray into the woo-woo, but there's actual science that has been done and is emerging that is just utterly fascinating to me. So think about a flower. You have this beautiful, bright thing produced by the plant and it smells good because it's trying to attract pollinators. But what some scientists I talked to have discovered is they're not only using those colors to attract pollinators, that flower is also an ear and it is listening for the pollinators in some cases.
So certain kinds of flowers, when a bee is buzzing closer, they start to sweeten up the nectar that they produce so that when that bee lands and takes a sip of their nectar, they're going to hang out longer and they're going to come back and they're going to tell their bee buddies like, "Hey, over here, this is a really good flower." And that to me is mind-blowing, because we make this division in Western science and in Western culture of like, there's plants and there's animals and never the twain shall meet, and plants we think of as these kind of inert objects more.
But here we've got examples of plants that are using sound to change their own chemistry to help them reproduce, to help themselves survive. And I just love that. It's like so many things are listening in ways that we would never understand or never expect, I should say. Another example going completely at the other end of the spectrum, elephants who we all love and they're beautiful and of course they can hear. They've got giant ears and all. So in some ways they're so much more relatable. They're mammals, they take care of their young. They can hear through their feet. They have these big pads on the bottom of their feet that are picking up vibrations from the soil. So an elephant moving across a Savannah can be two or three kilometers from another elephant and send out a signal and that it's buddy can be like, "Oh, okay, water hole this way." And they're walking off together without being able to see each other, making sounds that we can't hear that are traveling through the ground.
So even with animals like that that are so much more relatable, I think one of the things I just love about this is like, it's so humbling, like don't make assumptions. Yes, that animal is making sounds in ways that we can relate to. It's also making them and receiving them in ways that we would never expect. And it's just beautiful to me.
Shelby Stanger:
Do you have a favorite animal sound or maybe like a top three?
Amy Martin:
Okay. The first one that comes to mind I didn't hear in the wild, but I've heard recordings. A bearded seal making its mating sound is one of the coolest things you've ever heard. We can play it.
I just love the idea of this like chubby seal up in the Arctic, just like making this like, "Somebody love me." That is a very cool sound. Another really cool sound, this is a super weird one. There are these little bugs, they're called tree hoppers, and they're teeny tiny and they stand on like plant stems and they shake their abdomen against the plant stem. And if you and I are standing right next to them, we wouldn't hear a thing, but if you attach a microphone onto the plant so that it's actually capturing the vibrations in the plant, it is so loud and weird.
Some of them sound like kind of beautiful and melodic and some of them sound angry and like they're coming for you and they're like teeny tiny, like half an inch big and they're making these, like just bellowing into plants and other tree hoppers and other animals that are touching the plant can hear them. So it's this whole world of sound that we're completely oblivious to that's happening around us all the time.
Shelby Stanger:
Over the course of making this season, Amy heard all kinds of incredible sounds, bugs chomping through leaves, naked mole rats chirping, and even the robotic tones of turtles. But what do these noises actually mean? That's where technology comes in. The field of bioacoustics is advancing rapidly, and during production, Amy met many researchers who are recording vast amounts of audio data and then using AI to analyze it all.
Tell me about the people you met while you were making this season.
Amy Martin:
Yeah. One person who is just absolutely fascinating and so inspiring is Joyce Poole. She is probably the preeminent elephant listener on the planet right now, and she grew up partly in Kenya. Her organization is called Elephant Voices and she has just decades and decades of data of elephants, mostly in Kenya, but other African countries too, and has made all kinds of fascinating discoveries about what their different sounds mean. So that's one scientist who comes to mind who I would just highly, like just go to Elephant Voice's website and look through some of her videos and watch these amazing beings interacting.
When she started out, they were taking enormous heavy recorders out into the field that were like recording onto tape and big, expensive microphones that you probably had to like get some big fancy grant to buy this thousands-of-dollar microphone. And then taking these heavy tapes and going back and she would make notes, like physical notes and go back and listen to the recording and be like, "Okay, at minute 90 point, blah, blah, blah, so-and-so turned their trunk this way, and this is the sound that went with it. And so I'm guessing we get enough of these data points that when they make this sound with this motion, it means this kind of thing."
And that idea you can transpose across basically all of the different species. This is how it was done. But over the course of her lifetime, that morphed into lighter microphones and lighter tape and not tape and digital recorders that, wow, we can record for a whole hour. And now it's like we can record all day long, as much data as you could possibly ask for. And so one of the things that was really interesting to talk with her about, and she showed me just the unbelievable amount of digital files she has. This is kind of where AI comes in, because she and an army of people could spend the rest of their lives listening through everything that she's recorded and they would never get through it all.
And so these giant databases are partnering with some people that are doing really ethical versions of AI to say, how can we listen? How can we use a machine to listen through all that and mark like, okay, that time when that trunk moved that way and that sound was made, here's 50,000 examples of that recorded over the last 25 years. Now we've got some really powerful data that can start to tell us what that sound might mean. But even then, it's really hard because we can't go to the elephant and be like, "Did we get it right?" And so that's where this humility comes in. Even with AI, so many of the researchers that I talked to said like, "We have to constantly keep in mind that all we're going to have here are really good guesses for a long time."
Shelby Stanger:
I'm curious what the sounds that you're learning about are telling us about biodiversity.
Amy Martin:
Oh, that's a great question. And unfortunately, a lot of what the sounds are telling us about biodiversity is that biodiversity is decreasing, which is not going to shock anybody who listens to your show, but it's a way that we can actually track what is happening in a landscape. And this is a really important piece of it. When we start to do some conservation measures, we can see whether or not it's working. One of the super cool examples of this is actually back to coral reefs. The sound of a healthy coral reef, and you know this, I'm sure, is loud and dynamic and bubbly. There's fish talking, there's shrimp snapping, there's a million different sounds happening. And a degraded reef, one that has maybe gone through a couple of bleaching events is much, much quieter, and a dead reef is essentially silent. And you can hear that, you can track that and scientists are tracking that.
So it's a way of being able to know what level of biodiversity impact is a certain area having. And then this really cool project has been birthed in the last several years of people saying like, "Can we then actually use sound to help bring some of these reefs back?" And so one of the scientists I spoke with, Tim Lamont, took underwater speakers, like the kind that you use if you're going to do like... Oh, what is that called? Synchronized swimming.
Those exact same kind of speakers, plunked them next to a dead reef and played the sounds they had recorded from a healthy reef through the speaker. And lo and behold, it attracted fish and other animals back and they started chewing off the algae that they needed to get rid of and laying their eggs and bringing reefs back to life because of the sound. So it kind of told them like, "Hey, party's happening over here on this reef. Let's go join it." So sound can be a marker of biodiversity loss, biodiversity recovery, and it can also be a tool in biodiversity recovery, which is so inspiring.
Shelby Stanger:
That is so cool. That's just like if you've listened to positive self-talk, you're going to have a more-
Amy Martin:
Yes, exactly.
Shelby Stanger:
... positive life.
Amy Martin:
It's like self-help for fish.
Shelby Stanger:
And if you wake up and look at the doom and gloom of Instagram, your day is probably going to suck.
Amy Martin:
Yeah. Yeah. What we listen to, what we take in really matters. It really affects us. Yeah.
Shelby Stanger:
I love the idea that sound doesn't just reflect the health of an ecosystem, but can actually help restore it. It makes you think twice about what we're listening to in our own day-to-day lives, what we're turning up or tuning out. The science that Amy explored in this season suggests we might be on the verge of understanding a whole lot more of what animals are saying. In fact, she told me she thinks we're probably not far from having an app that can decode our dogs barking. In making this show, Amy learned that there are countless ways that plants and animals communicate, which humans cannot detect. When she released this season, she hoped that her audience would be as interested in radical listening as she was.
Did you have any challenges in making this show?
Amy Martin:
I would say one of the challenges that I think is an interesting and a good challenge to take on is just my own questions about, can I expect, can I hope an audience will listen to episode after episode where humans are not the center of the story? Because as a storyteller, you know that what people want to know is who are you? Why are you doing the things you did? Where are the conflict points? How did you overcome adversity? All these things.
Shelby Stanger:
How does it relate to me?
Amy Martin:
How does it relate to me? Yeah. And that's totally fair. I mean, that's how our brains are wired. We can't change that about who we are, but I really wanted to take the risk of challenging myself and the audience to put somebody else at the center of the story. There's still drama, there's still narrative arcs and there's still adversities to be overcome, but not necessarily with humans and our needs being the primary thing. And I actually think it's relieving, to me, it's relieving to turn my attention to those stories and to those voices. It's like my story might matter, but it's just one among this whole mosaic. And I think that that, for me, helps me feel more connected in a certain way.
Shelby Stanger:
Yeah. I think there's a lot of navel-gazing going on right now. And when our team told me we were interviewing you, I was like, "Yes, this is so awesome." This is a story that makes me feel small and makes me feel like I'm in a bigger world. And also, there's mystery. Everything in our world right now is so predictable and we know a lot, but this is like a frontier that we don't know about. So I think our minds are hardwired for discovery.
Amy Martin:
Yeah. And I feel like as a surfer, you know, when you said it makes me feel small, and like you said that with a positive vibe. And I think that you know that experience. I'm not a surfer, but I can imagine, and I've been in other situations where being small can be so wonderful. To feel the tininess of you against the force of the ocean must be so amazing. And I think that that's something that we kind of need culturally right now, just to understand our own smallness, partly as a way of just calming down, taking a breath. It's not to avoid our own problems, but to be able to approach them with a little bit more grace and space for each other, maybe.
Shelby Stanger:
Yeah. I actually prefer snorkeling right now as like my favorite activity, and it's because you can see so much and there's this entire world under us that we just don't know about it. It's the most calming activity, but I've never thought about it through the sounds. I can hear seals chirping at each other, yelling at each other. We see them getting angry. We see them like, it's pretty wild. Every night at sunset, you can see this live at La Jolla Cove. It's the best movie that's free. But yeah, it's so interesting. So I'm curious what you've learned about radical listening that you can share with us that can be beneficial for us.
Amy Martin:
Well, first of all, when you say being underwater, I'm just immediately flashed onto my first and only snorkeling experience, again, off the coast of Australia. And I think just the physical fact of putting a bunch of humans with a thing in their mouth so they can't talk, you're basically muted. And just that alone, I love jumping off the boat with a bunch of strangers and we're like, We can't talk to each other. We can go... You know? And then to be surrounded by the amazing sounds and the beauty of coral reef, oh my God. I just, I'll never forget it. I can't wait to snorkel again.
But there's something from that that I think any of us can take of what happens if I'm in an argument and I just decide to essentially put the imaginary snorkel in my mouth and just be like, "I'm going to be in the position of taking in what you're saying for a while." It doesn't mean that I'm going to abandon all my own thoughts or ask you to do the same and get my... But what if I just take the position of the radical listener? How does that change the dynamics of the argument, of the conversation, whether it's in real life or online? And if you do it, it feels good. I think it's a relief to stop talking and listen.
Shelby Stanger:
It's fascinating that nature speaks and listens in ways we're just beginning to understand. I'm looking forward to seeing how this research and technology develops in the coming years. You can find Hark, the most recent season of Threshold wherever you listen to podcasts, and you can learn more on their website, thresholdpodcast.org, or on Instagram @thresholdpodcast. You can also find Amy online at amymartin.com. That's A-M-Y-M-A-R-T-I-N.com. Thank you to Miles Parsons, Rex Cocroft, and Gabriel Jorgewich-Cohen for letting us use your animal sound recordings in this episode. Wild Ideas Worth Living is part of the REI Podcast Network. It's hosted by me, Shelby Stanger, produced by Annie Fassler, Sylvia Thomas, and Sam Peers Nitzberg of Puddle Creative. Our senior producer is Jenny Barber. Our executive producers are Paolo Mottola and Joe Crosby. Thanks again to our partner, Capital One and the REI Co-op Mastercard. As always, we love it when you follow the show, take time to rate it and write a review wherever you listen. And remember, some of the best adventures happen when you follow your wildest ideas.