Hark | 1 | The Slime of Life

back. Okay. Are you ready? Three, two, one. What did you hear? Could you hear any sounds that weren't made by people? If so, consider yourself lucky, because human beings have become very, very loud.

own. If the planet is a dinner party, we're the guests who are ruining the conversation, talking over everyone, assuming that our voices are the most important ones in the room. We're drowning out essential communication between other creatures, forcing them to spend their lives shouting to each other in order to be heard, or worse, we're silencing them forever. And our noise doesn't only threaten other beings. We're endangering ourselves, and we know things are out of

balance. We feel isolated and cut off because we are.With multiple ecological crises mounting around us, many of us feel desperate to help, and there is unquestionably so much work to be done, but maybe the first step is slowing down and letting the voices of our planet mates back in. What if being useful starts with being quiet? What if saving the world begins with listening to it? What changes when we remember to listen to the more than human world? That's the

question at the heart of this season of our show. Despite all the damage that's already been done, there is still a vast planetary choir singing around us. It's right there waiting for us, if we turn our attention to it. All over the world, people are hearing those voices and responding. We are in the midst of a listening emergency, but

also a listening Renaissance. In this season, we'll meet people who are devoting their lives to listening, reconnecting with old traditions, or creating new ones, and building tools that might someday allow us to comprehend what other animals are saying in ways we've only dreamed of in the past. It's going to be a fun journey and a fascinating one, but I'm going for something deeper than the wow factor of cool nature

sounds. I chose to make this season now because I think all of our ecological crises, climate, extinction, pollution, are essentially breakdowns in relationship, and the first step in healing any broken relationship is listening. So what happens when we do that? Welcome to threshold. I'm Amy Martin, and this is season five. Hark. It's seven o'clock on a sunny morning, and I'm on a boat heading into Shark Bay, a huge marine reserve off the Western

Australian coast. This is Malgana country, one of hundreds of Aboriginal groups in Australia, and in malgana, the name of this place is Gathaagudu, which means "two waters." Dr. Stephanie King: Dolphins straight ahead. We've barely left the jetty, and Dr. Stephanie King has already spotted a dolphin. It surfaced and disappeared again in a flash, but that was enough time for her to identify it. It was a female named Gindy. You knew who it was that fast?

Each nick is kind of similarly spaced along the fin, almost equidistant from each other. So each dolphin has a unique dorsal fin, like we say, like a fingerprint, but it's far more obvious than that, I guess, like a human face. So they're very distinctive. If you've been working with them a long time, then then you recognize all the individuals. Shark Bay and its surrounding coastal areas are listed as a UN World Heritage Site, and it's easy to see why.

The water is a clear turquoise blue and huge sea grass meadows provide food and shelter for an abundance of wildlife. Sea turtles, dugongs, and more than 300 species of fish, including the namesake sharks. But the superstars here are the dolphins. The scientists of Shark Bay Dolphin Research have been studying them continuously since 1982, making this one of the most carefully observed communities of dolphins on the planet. Stephanie is one of the current co directors.

Do you know how many dolphins are here, roughly? Dr. Stephanie King: Two to 3000 I mean, there's about 1800 that we have in our catalog that we work on, and that's just in our core study area, in the eastern Gulf. There's far more than that. And of those 1800 how many of them can you identify on site like you just identified that one in two seconds? Dr. Stephanie King: I've never tested myself, but maybe we could do that. I know a lot. More, way more than 200. And when did you first come here?

Dr. Stephanie King: I first came to Shark Bay in 2014, so 10 years ago now. And have you been coming almost every year since then? Dr. Stephanie King: Every year. I think 2020 was the only year because of COVID, but I come every year, and it's a really important part of my, I guess just part of my life, coming here, spending time with the animals, being inspired for the next questions that we want to answer, seeing who's still around, who's had a calf, how are the males doing, who's

allying with who? I think this is certainly where I'm at my most happiest as a field biologist. It's where I'd like to be most of the time, if I could. Yeah. Stephanie studies these dolphins using every non invasive tool,

all booming right now. Over the course of this season, we're going to meet bioacoustics researchers working with all kinds of different creatures, but we're going to dive deep with dolphins. Pun intended. We'll be returning to Shark Bay in several episodes in hopes of really getting to know this team and the way these remarkable animals are using sound Stephanie says that starts with learning about the dolphins world overall, their habitats, their relationships, their needs and preferences.

Dr. Stephanie King: So we look at behavioral complexity in bottlenose dolphins, and that can take the form of foraging specializations and tool use, which is a great example of animal culture, but we also spend a lot of time looking at cooperation. This is really where my passion lies, understanding how animals use communication to mediate complex social behaviors like cooperation. Highly social animals like dolphins, elephants

and people have special needs for communication. We make decisions together, like where to find food or how to respond to a threat. We maintain long term relationships that we depend on in times of need, and we pass on information to our young. All of this cooperation demands that we develop complex communication skills. Dr. Stephanie King: And in Shark Bay, we have male dolphins that form long term alliances. So these are really significant

relationships for these animals. They're investing heavily in these cooperative relationships with each other, and I'm really fascinated by the ways that they do that. So what vocal signals are they using to mediate these relationships? How do they keep track of each other? How do they coordinate their behavior? So these are all the types of questions that we aim to answer in our work in Shark Bay. Is the cooperation that they're engaged in, how much of that is happening through sound?

Dr. Stephanie King: It's mostly happening through sound, and that's because it's a species that lives underwater, right? So vision is restricted because light doesn't travel that far. They have good visual acuity, they've got good vision, but they don't rely on vision because they can't see that far underwater. But sound travels really far. Dolphins use other forms of communication too, of course.

Dr. Stephanie King: They can be quite tactile with each other, so they'll spend time petting and rubbing each other, and that's a way of reaffirming or establishing or maintaining relationships. But Stephanie says sound is central. Dr. Stephanie King: They use sound for all important aspects of their life, to navigate their environment, to find food, and, importantly, to communicate with each other. So it's their primary modality, it's sound, it's not vision, it's not

gestures. And by sharing information through vocal signals, they can let each other know where they are, maybe if they plan to move, if they want to reunite this type of information. When I visited the team in May of 2023, they were just getting started for the year. Amelia, who goes by Millie, is a recent master's graduate who's here to get experience as a research assistant. Laura is a PhD student collecting data for her thesis work.

traveling, resting, and then we look at who are they with. And by doing that throughout the season, over multiple years, and we've been doing it for 40 years now, we have this incredible picture of who associates with who, who has strong friendships,

which dolphins avoid each other. And we can, like, map the social network, if you like, and we can look at the structure and maybe link some of that information to fitness measures, like, does being more sociable mean that you're more successful and you have more offspring, for example. You got dolphins, Laura?

Dr. Stephanie King: If we see splashes, we'll check just to make sure it's not dolphins foraging anything that looks like it could be a dolphin, or indicate dolphin behavior we'll check with the binos and maybe even go a bit closer. I quickly get obsessed with dolphins spotting myself, which was a little dangerous. Stephanie told me that if someone says they see a dolphin and it turns out to be a bird, they have to bake something for the rest of the group back at the Research Station.

dolphin we see. Millie will write down notes, and I'll just try to stay out of the way. Dr. Stephanie King: We have Zeppelin and Blimey. Hands on the steering wheel and eyes on the water, Stephanie calls out the name of each dolphin to put into the notes. Dr. Stephanie King: Z-E-P, and B-L-M. Yeah, you got them. They might come again they're still just beneath the surface. They're so close! Stephanie is mindful of keeping some distance, but the dolphins

aren't as concerned about the rules. They swim close to the boat, zipping around and seeming to check us out. When they swim over dark patches of sea grass, they can all but disappear, and then all of a sudden, they pop up again to grab a quick breath. Even though I can see them coming, it's delightfully startling every time they crest the surface. These are Indo-Pacific bottlenose dolphins, smaller than some

other species, but still big. They average around two and a half meters long, or more than eight feet, with a maximum weight of about 230 kilograms, or about 500 pounds. But all that bulk doesn't limit their grace. It's actually hard to call what they do swimming. It looks more like dancing or flying. Their smooth, shiny bodies roll past us in a heartbeat as Laura tries to get a clear portrait of each one.

think it's Juicy. Blimey's on the bow. Hey guys. Both on the bow. Oh wow, right under the surface. And then they're gone again. It's shocking how quickly a group of 500 pound animals can just disappear. The four of us stand in the boat looking in four different directions, waiting, watching. We know they're nearby, but we don't know exactly where or when they might pop back up to take a

breath. Stephanie uses the temporary pause in activity to look over Millie's notes and tell her what needs to be added. Dr. Stephanie King: So the five minute information would be travel. There are two other animals here. They're back. Stephanie interrupts herself to call to Laura, telling her that Juicy is not the only dolphin that has joined this group. There's another one, so far unidentified. Then she quickly turns back to Millie. Dr. Stephanie King: Travel, regular, straight, slow, tight.

There's a lot happening all at once, with dozens of these kinds of teachable moments every hour. And Stephanie has to find a balance between making sure the data get collected correctly and giving the younger researchers freedom to do things themselves.

to fit in to dolphin society. I can't help but notice some parallels between the animals in the water and us humans up in the boat. All together, we're a total of eight mammals working in two teams using acoustic communication to learn from our leaders. And then for me, came one of the more magical moments of this experience. We have a speaker! So we're hearing in the hydrophone.

Laura has flipped on a speaker in the boat, so we can hear, in real time, the conversations the dolphins are having in the water around us. Suddenly, we're with them in a completely different way.

why they matter. I want to ask Stephanie a lot more about the male alliances that she studied and how they use sound, but right now, it's time to take a deep breath and appreciate where I am and what I'm getting to witness. I don't have to understand at all to know that I have just been visited by wondrous beings, creatures full of beauty and power and intelligence, and they've survived on this planet for millions of years by listening to each other. We'll have more after this short break.

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We've explored the subtle nuances of the human voice. We have to remember that humans, over many hundreds of thousands of years of evolution, have become extremely attuned to the sounds of each other's voices. And we've revealed why a famous composer wrote a piece made entirely of silence.

earthquakes, ocean waves, volcanos. And that's how things were for a really long time. The Earth is around four and a half billion years old, and for about 90% of those years, nothing existed that was capable of intentionally making a sound or receiving it. So how do we get from that world to this one? How did the Earth transform itself from a place of such

unfathomable quiet into a non stop symphony of sound? We're going to spend the rest of the season telling that story, tracing the sonification of the Earth roughly in the order in which life evolved. It all started with a silence too long for us to truly comprehend, but I wanted to try, and it turns out one of the best places to do that is just down the Western Australian coast from where I met the dolphin researchers.

Okay, I'm just in the parking lot. Pardon me, just in the parking lot for the Hamelin pool. I leave behind one talkative Australian Raven and a small flock of chiming wedgebills and walk the short distance out to the edge of Hamelin pool, a big bay with a surface smooth as glass. I just want to try to listen here for a little while. The water is so still. There's not a ripple, there's not a there's no birds landing on it. There's no bubbles or any sign of movement.

It's early, and I'm alone. But those aren't the only reasons this place is so silent. Hamelin Pool has an inner stillness. It's extremely salty, twice as salty as the open ocean, which means it's hard for plants and animals to survive here and against this canvas of quiet, every sound made by a living thing pops out, a bird peep, a fly buzz. For most of our planet's history, this kind of silence reigned supreme.

Just think about the entire earth being that quiet. There was nothing, breathing, flying, walking, crawling, a whole planet with nothing that had a voice. But although Hamelin Pool may be a profoundly quiet place, it isn't actually as lifeless as it seems. There's a lot of mysterious blackish gunk carpeting the beach in front of me, almost like a bathtub ring of slime growing where the water

meets the shore. These are communities of microbes. They go by sexy names like gelatinous microbial mats or pustular sheets, and they built a bridge between the barren early Earth and the lush, loud, fruitful world we enjoy today. Ancient microbes were the inventors of what is arguably the most important technology of all time, photosynthesis. A couple of billion years ago, they started to tap into the sun's

energy and produce oxygen, and that changed everything. Bit by bit, they pumped that oxygen into the sea. Dr. Erica Suosaari: You know, and after a while, then all that oxygen created by photosynthesis from microbes, eventually saturates the ocean, the ocean can't hold anymore. Where does the oxygen go? It goes into the atmosphere. This is Dr. Erica Suosaari.

Dr. Erica Suosaari: The atmosphere becomes oxygenated, which essentially that allows for evolution, which then here we go, and finally get to us. The slimy mats I saw growing in Hamelin Pool were microbes still performing these ancient rituals, doing the work that led to all other life on Earth. They don't look like much at all, but they hold the origin story of every call, cry, squawk, or song ever heard.

Dr. Erica Suosaari: This is a living system still doing this, still doing these same processes that were happening billions of years ago. There is no place else on the planet that represents that in its entirety. It is really this window into the ancient. I'm curious about you, like, what, what stage in your development did you realize, I really want to learn a whole lot more about goo? Dr. Erica Suosaari: I guess technically I'm a marine

geologist. I'm a carbonate sedimentologist, but I look at marine rocks. Erica is based at the Smithsonian Institution's National Museum of Natural History in Washington, DC. She first visited Hamelin Pool while working on her PhD, and she was so blown away by the glimpse it provided into the early Earth that she moved to Western Australia and lived close by for several years, just so she could continue studying the place. Dr. Erica Suosaari: So I have sort of this obsession with

time. I've always had this obsession with time and kind of infinity and what it means and the big picture and how significant our lives are and what we do, because the time is so big, and it's like, you know, kind of figuring out the puzzle of what life means on huge scales. And key pieces of that puzzle can be found in

these communities of microbes at Hamelin. Erica is one of the world's leading experts on them and the stony structures they create, which are called- Dr. Erica Suosaari: Microbiolites, which are basically rocks created by microbes. We don't tend to think of microbes as creating anything except infections, maybe, but at some point, way back in time, they started to make rocks: clotted thrombolites, branched dendrolites and layered

stromatolites. The world's oldest fossilized stromatolites found in Western Australia are almost three and a half billion years old, and the microbes at Hamlin pool are still making these rocks today. It's the largest known collection of living marine stromatolites in the world. Dr. Erica Suosaari: What Hamelin represents is, is, I don't even have a word for what Hamelin represents. It's just, it's a really spectacular place. It's a living laboratory. The stromatolites are kind of like the Machu

Picchu or Egyptian pyramids of the microbial world. These are structures made by communities of living things with a story to tell. They grow close to the edges of Hamelin pool in the shallow water, maybe a foot or two high. Some of them look a little bit like toadstools, others resemble stubby fingers or brainy mounds. But whatever form they take, there's

something about them that signals life. You can see familiar, organic patterns in them, you can sense that they grew, and this is how it all began, even though the microbes themselves are very quiet, without them, there would be no voices to speak or ears to listen. Erica says one of the essential ingredients in this process is a coding the microbes make and cover themselves with. Dr. Erica Suosaari: It's called EPS. It's exo-polymeric substance.

Exo-polymeric substance. I asked her to translate that into non-sciency language. Dr. Erica Suosaari: It's like a, it's this. It's this. It's the slime of life. You know? It's like a, it's a goo. It's a goo. We've got a microbe that makes a goo. Dr. Erica Suosaari: Yeah. As sediment in the water floats by, some of it sticks to this goo, kind of like dust sticking to fly paper. It builds up layer after layer into stone. Dr. Erica Suosaari: And you build up kind of this laminated

structure. So that's a stromatolite. The EPS can actually do all kinds of cool stuff. It helps the microbes communicate with each other. It acts as a sunscreen. It even changes the chemistry of the water, which helps in the stromatolite building process. So it's a it's a self produced goo that does chemistry. Dr. Erica Suosaari: Yes, or has chemistry happening. Yeah, all around it. Okay, there's like, a lot going on. Dr. Erica Suosaari: Oh yeah, there's a lot going on.

I like to think of these microbial communities as the world's first cities, with the bacteria in them bustling around, working as architects and engineers, carpenters and chemists. They farmed sunlight and produced oxygen, the oxygen that led to me talking to you right now. Dr. Erica Suosaari: These lineages of bacteria, life persisting for billions of years.

While everything changed around them again and again and again, these microbes carried life forward, passing it on and on and on, one generation after another. Dr. Erica Suosaari: It's not a timeline that I still think I can wrap my mind around, but I find it sort of comforting that there is this long stretch of time that these rocks represent, and I am drawn to that. What do you think the world sounded like when the only living things were these microbes.

Dr. Erica Suosaari: Cashing waves. I don't know. A lot of water. But underwater,there's something about silence. I can't imagine. I mean, silence. What does that sound like for oxygen bubbles to rise to the surface, crashing waves? Kind of meditative and calm, which is crazy, because it's a time in Earth's history where it's very chaotic, and, and yet, you know, there's like the kind of the peace that life brings. As I stood on the beach at Hamelin Pool, I tried

to imagine more than 3 billion years of that silence. Eons of ear splitting emptiness. And rhen finally, the planet began to sing. Every song or call or cry made on Earth happened in just the last tenth of the planet's existence. The cacophony of life that we take for granted is actually exceptional. Silence is the norm on our planet, or any planet that we know of. Erica's work is being used in the search for life on Mars, and maybe someday we'll receive communication from

some extraterrestrial being. But so far, we Earthlings are singing together into the void. The only voices we've ever heard are each others'. This episode of Threshold was written, recorded and produced by me, Amy Martin, with help from Erika Janik and Sam Moore. Music by Todd Sickafoose. Post-production by Alan Douches. Fact-checking by Sam Moore. Special thanks to Tim Lamont and Miles Parsons. This show is made by Auricle Productions, a

non-profit organization powered by listener donations. Deneen Weiske is our executive director. You can find out more about our show at thresholdpodcast.org.