You’re listening to Everything Environment by Mongabay-India. This is Wild Frequencies, a three-part podcast mini-series.

[Phone rings. Researcher Vijay Ramesh picks up the call.]

“Oh, coming coming. There’s a trogon there. Let’s go”

[Everyone starts running.]

Shreya Dasgupta (SD): Welcome back to Wild Frequencies. I’m Shreya Dasgupta.

Kartik Chandramouli (KC): I’m Kartik Chandramouli. This is the podcast in which wildlife researchers from India share their stories of sounds from the animal world. And they decode those wild frequencies for us, one song, one howl and one chirp at a time.

 SD: This is our third and final episode. If you haven’t heard the previous episodes, we urge you to hit pause, and go and listen to them first. But if you have been a loyal listener, then thank you for staying on this journey with us!

KC: But we’ll still do a quick recap. In the first episode, we heard from researchers who use sound to find animals and count them. In the second, we spoke with scientists who use sound to know animals, to understand their behaviour.

In this final episode, we explore a different idea. We humans, have altered most of the environment around us. We have cut forests and tried to create new ones.

SD: We have cleared grasslands and replaced them with farms and industries.

KC: We have built roads and railways that slice through landscapes.

SD: And we have expanded our towns and cities. All in the quest of making our lives convenient.

KC: But how have animals adapted to these changes? Once again, can bioacoustics help us understand this in some way?

[Airplane announcement]

SD: To find out, Kartik and I flew to Coimbatore in Tamil Nadu in March this year. We landed at the airport, had a quick breakfast of idlis. Then we hired a cab, and drove a little over 100 kilometres towards a place called Valparai. It’s a small plateau at an elevation of about 1,000 metres. And the car ride involved going up more than 40 hairpin bends.

[Kartik interacts with the cab driver.]

KC: Hairpin bends, I absolutely hate.

[SD: On a scale of 1 to 10 how motion sick are you feeling ?
KC: I am at a 4.5]

KC: But just as the bends end, the scenery…becomes picture-perfect. On one side of the road — dense rainforests of the Anamalai Tiger Reserve, and a carpet of lush green tea estates over undulating hills on the other side.

All the illustrations and paintings that we see (of Valparai), I’ve only seen with tea plantations.

SD: But once upon a time, Valparai was mostly rainforests. Was. Sometime in the late 1800s, some Britishers started clearing the forests, one area at a time. In their place, they planted coffee and tea. Although eventually tea became the crop of choice.

Shankar Raman (SR): And today the landscape has…more than 80 percent of  it is under a monoculture of tea plantations. But within those tea plantations, there are a number of forest patches.

I’m Shankar Raman, a scientist with the Nature Conservation Foundation.

Divya Mudappa (DM): I’m Divya Mudappa. I also work with Nature Conservation Foundation as a scientist.

KC: Both Shankar Raman and Divya Mudappa have worked in Valparai for nearly 25 years. So, on our second day there, Shreya and I went to meet them because: 1) they know Valparai very intimately, and 2) because they have been instrumental in a rather audacious experiment. Remember Shankar Raman said this?

SR: Within those tea plantations, there are a number of forest patches.

We’ve identified nearly 70 forest fragments ranging in size from less than a hectare to more than 300 hectares.

SD: When Shankar Raman and Divya started working in Valparai, most of these forest fragments within the tea plantations were very degraded. Imagine logged trees everywhere, a sparse understory, and lots of non-native weeds.

SR: Each site had its own history, depending on what exactly had happened there. So, the causes of degradation were different, but as a result, today, if you entered many of those forest patches, they would have maybe one third to less than half the density of trees as an intact forest would have. They would have only a subset of the trees that the other forests would have. They’d have a lot more weed cover which was suppressing the regeneration.

KC: Now, tea crops by themselves don’t hold much value for wildlife. But the two ecologists saw great potential in the degraded forest fragments within the tea estates.

SR: The plateau itself is surrounded on all sides by larger protected areas. It’s the Anamalai Tiger Reserve in Tamil Nadu, and on the Kerala side, we have the Parambikulam Tiger Reserve and other reserve forests. So, since it lies in the centre, it’s actually very valuable for a lot of wildlife that continues to persist in the fragments and also moves through the landscape.

KC: Wildlife like wild dogs, elephants, gaur, Nilgiri langurs, lion tailed macaques and lots of birds like great hornbills.

[Auto rickshaw starts.]

In fact, we took an auto-rickshaw to generally see what’s in Valparai. And it turned into a mini safari. We saw a troop of lion tailed macaques resting over rooftops in the town. We also saw a massive herd of gaur sauntering through a tea estate and just when it became dark, elephants walked out of a forest patch into the same estate. At the end of the day, our hotel owner showed us CCTV footage of leopards just outside his place. In a few hours, we had enough proof that there’s plenty of wildlife using the landscape.

SD: So, back to Shankar Raman and Divya’s audacious plan. They decided that they would give all this wildlife a helping hand. And they would do it by restoring the degraded forest patches within the tea estates. But because the forest patches lay inside these estates, they had to convince the plantation companies of their plan. It took nearly two years of negotiations and conversations, but the duo managed to get the estate owners on-board. And in the early 2000s, they started actively restoring the degraded fragments. It’s something that they continue to do even today.

DM: We are restoring to what the mid elevation rainforest within the Anamalai Tiger Reserve looks like. In this case, that’s our benchmark site. And these sites are, anyway from low altitude rainforests to higher elevation montane evergreen forests.

KC: To get to these target forests, the team collects seeds of rainforest trees from within Valparai itself, from forest trails and forest edges. Then, they take those seeds into a nursery that they have created. They raise and nurture the saplings for a few years, and then plant them within the fragments.

DM: Our activity involves removal of invasive plants like lantana or Mikania or whatever, making sure that whatever is naturally regenerating is left behind, including pioneer species like Clerodendron or Macaranga.

SD: Pioneer species are the ones that are first to colonise a disturbed area.

DM: And within that, after an assessment of what is growing there naturally, we plant a very high diversity of rainforest plants, mostly trees. And when I say high diversity, we plant anywhere between 50 and 80 species per hectare. And about 800 to 1,000 plants per hectare.

SD: Since the early 2000s, Shankar Raman and Divya say that they’ve been actively restoring over 20 degraded forest fragments. They have also left some degraded fragments to regenerate naturally without their intervention – these serve as a control, you know, to compare if active restoration like the researchers are doing, is better or worse than just letting nature take its course.

KC: Visually, the researchers have seen the restored plots look more like rainforests every passing day. But since they are ecologists, they wanted data to confirm what they were seeing.

SR: So, first of all, is the forest recovering is a question? And secondly, are fauna responding to that change and coming back along with the forest?

KC: To answer the first part, one researcher Anand Osuri studied the recovery of trees in the various fragments. And he found that yes, the sites that had been actively restored, they are looking more like the targeted rainforests. Much more than sites that had been left to naturally regenerate.

SR: So that came about, saying that, yes, ecological restoration can lead to forest recovery. And it’s better than hands off, nature knows best, let, let the forest recover on its own in this kind of a fragmented landscape. But we still didn’t know whether fauna were responding to that and whether they were coming back.

SD: To answer this, an ecologist Priyanka Hariharan picked a fauna to study: birds. She wanted to know whether birds were returning to the actively restored fragments. And her surveys were more of the traditional kind. She would physically visit different points in a fragment, then ID and count all the birds that her team could either see or hear.

Vijay Ramesh (VR): So, I was tagging along with Priyanka, who was doing this study, trying to document if birds are returning to these restored fragments.

I’m Vijay Ramesh and I’m a postdoctoral research scientist at the Lisa Yang Center for Conservation Bioacoustics at the Cornell Lab of Ornithology.

KC: We went to Valparai on Vijay’s invitation, and we spent an entire day with him and Priyanka – who are now married to each other.

VR: I was tagging along with Priyanka, who was doing this study, trying to document if birds are returning to these restored fragments.

And we very quickly found out that most of the time that she was recording birds, it was often by ear rather than by visual observations. So we thought, okay, we can replicate the same study and we can use audio recorders.

SD: Vijay’s idea was simple: he wanted to figure out what birds visit the three kinds of fragments: First, degraded sites that Shankar Raman and Divya’s team is actively restoring. Second, degraded sites that are left alone to naturally regenerate. And third, undisturbed intact rainforests, which they also call benchmark sites. But instead of doing traditional surveys, Vijay wanted to use audio recorders in all these places to listen for the birds.

[Vijay Ramesh gets down from car to show us the recorders he uses.]

The car’s trunk is opened. Vijay the opens a bag and shows us the recorder.

VR: So, here’s a recorder.

KC: Is that a case around it?

VR: There’s a water proof case around the recorder. This is what we have been using for the last couple of years. These are AudioMoth recorders. So, they basically fit in the palm of your hands.

KC: AudioMoth is a brand of acoustic recorders. They are really tiny, about the size of a matchbox and the top looks like a green chip from inside your computer. Inside, it has a microphone that can record both audible and ultrasonic frequencies, which means it can record sounds from animals that we can hear, like birds, but also animals like bats and insects that may call in ultrasonic ranges. Whatever is recorded gets saved to a microSD card.

VR: It is very convenient because you can take 30-40 recorders at a stretch in your bag and go deploy them. You have a memory card here, just three AA batteries. And you have a USB B connection to your laptop to configure it.

SD: On your laptop, you can set a schedule. For example, do you want the recorder to record continuously all day long, or only during certain times of the day?

VR: So, we decided that we wanted to place audio recorders between January and May, late December to May, I would say. And, essentially in each location we wanted to collect audio data for three weeks at a stretch and then repeat it again a month later. That’s how I would say it got started, in terms of collecting audio data.

SD: After recording audio data for a while, one of the first things that Vijay and his team would do was to transfer the recordings from the memory cards, and listen to random clips, for fun. And they found lots of animal calls that you don’t get to hear easily. Like the cackling of giant squirrels.

[Giant squirrel cackling.]

The haunting hoots of Nilgiri langurs.

[Nilgiri langur hoots.]

The strange sounds of dholes or wild dogs. Warning: This might be a bit scary.

[Dholes call.]

They also heard birds that we otherwise tend to miss.

VR: You’d be surprised to hear like calls of like nocturnal birds, like because no one’s actually going out, placing a handheld recorder at four in the morning and you’re hearing these frog mouths, the Sri Lankan frog mouth, the spot bellied eagle owl and other nocturnal taxa that you wouldn’t, you know, otherwise hear during the day, right?

KC: Then came the actual analysis of bird calls in the three kinds of fragments. But this was challenging because they had thousands of hours of recordings.

You might think that if there are apps like Merlin that can identify birds through sound, couldn’t Vijay use something like that? Well, Vijay says that existing AI algorithms that automatically ID birds through sound – they may be good for common birds in our Indian cities, but they’re not reliable to use for most other birds in the country.

VR: I would say at least for Western Ghats birds, for some species, we are soon reaching a stage where we can, you know, rely on some of these algorithms. But for vast parts biodiversity in India, we still don’t have that training data to begin with. So, I think one of the goals that we want to get out right now is we want to collect audio data from different parts of the country. And it requires a lot of laborious effort, you know. You need to sit and annotate the data, find out what species are there, draw boxes around those vocalisations.

When I was doing my PhD, I was very lucky to work with two students, Akshay Anand and Meghna Srivathsa, and they both manually annotated over 80 hours of data each.

SD: When they analysed the data, they found that yes, if you actively try to restore degraded forests, birds will respond to your efforts, and start visiting. Vijay saw this with rainforest bird species, for example– species that like to live in good rainforest habitats. Like the Asian fairy bluebird, the great hornbill, Malabar grey hornbill, and the Malabar trogon.

[Rainforest bird calls play.]

Vijay’s recorders picked up calls of birds like these most in intact rainforests. That’s understandable. But next came actively restored fragments, where the recorders picked up plenty of rainforest bird calls too. And last came, naturally regenerating ones, with much fewer calls.

KC: In fact, we had an incident next to a restored forest fragment. We were walking with Vijay on the road. Priyanka had gone ahead with her interns to observe birds. And then Vijay’s phone rang.

[Phone rings. Vijay Ramesh picks up. “Oh, coming coming. There’s a trogon there. Let’s go”]

Vijay Ramesh and the podcast hosts start running.

SD: You’ve never seen a trogon here, but only heard it in your recordings?

VR: That’s right. I’ve never seen a trogon here in Valparai. When we deployed the recorders, we kept getting recordings. But I was bummed that I never saw them.

KC: How does it sound, though?

[Priyanka and Vijay try but fail. Laugh.]

KC: During their study, Vijay and his team didn’t just look at individual bird species, though. They wanted to understand all the different animal sounds you could hear in each of the different fragments. Did the benchmark, intact rainforests, actively restored fragments, and naturally regenerating patches all sound the same? Or were they different?

VR: And so, you could basically pick, say, a particular day, say, 12th March at 4pm, and I could listen to what it sounds like at all three sites at the same time. And you would hear that the soundscapes are distinctly different. You would hear a lot more sounds in these benchmark sites. In the restored sites, you would hear fewer sounds of certain taxa. And in the unrestored, much fewer sounds.

SD: Vijay and his team didn’t just listen to the soundscapes. If you remember episode 1 and 2, researchers like to visually see sounds as spectrograms. Because the graphs reveal a whole lot more, with ‘frequency’ on the Y-axis and ‘time’ on the X-axis. That’s what Vijay did too.

VR: But after we visualised it, you can visually see that some of the frequencies that we can’t hear, say above like, say, 15 or say 18, 000 hertz, etcetera, there are vocalisations of different insects and other taxa that are vocalising at that particular range. And you will see that those ranges were sort of missing in the restored forest and the unrestored sites. And that’s not something that I can hear by just, you know, listening to the sounds.

KC: Basically, the spectrograms showed Vijay that there was a large chunk of frequencies missing from the restored and naturally regenerating forests. But these frequencies were visible in the spectrograms of benchmark, intact rainforests.

We asked Divya what she thought about this finding.

DM: We were also fascinated to find that the soundscape or the acoustic space was so full in our benchmark sites. And in our restored site, there was this huge void, which we suspect are mostly insects. They still have not really recovered and at least they’re not calling and have not established. But of course, it’s still slightly better than unrestored sites. So, we know that there is some recovery and restoration is really a slow process and we need to stick to it for a much longer period of time. And feedback like from Vijay’s research really helps us to then target as to “What is it that we need to do better?”

SR: The thing that I think this work also points out or sort of underscores, it’s something that we knew earlier, or we’ve been saying, is that restoration cannot replace an intact or mature rainforest.

KC: That’s Shankar Raman.

SR: And very often it’s believed that, okay, you can, destroy a forest, you can degrade an area. It’s okay, because we can restore it. And there are many positive examples of restoration, including our work. It has been projected as a positive example of how restoration can succeed. But what it says is it can only succeed that far. And there is a lot that’s still missing, whether it’s the insects or even in among the plants, the epiphytes. So, you cannot use restoration as an excuse, to degrade intact forests. Protecting what is intact is very important.

[The hosts and researchers travel to Matha Junction.]

[Sounds of car doors opening and closing.]

SD: After our interview, Vijay drove us to a place called Matha Junction in Valparai. Where we got down, there’s a small tea shop by the side of the road. Priyanka went off for a cup of tea. Meanwhile, Vijay took us down a forest trail right next to it.

VR: We have just come from Valparai town. This was formerly a degraded forest patch. When I look at photos it’s so hard to believe that this particular patch has recovered so much in terms of flora.

SD: What did it look like before?

VR: It was pretty much like a barren land. Barring like a couple of tree species, there was nothing here. It was degraded…some weeds in the understory. That’s about it.

SD: We’ll paint a picture for you. When you enter the forest trail from the junction, there are two thin slivers of forests on either side. Sometime in the 2000s, Shankar Raman, Divya and their team began actively restoring the patch on the right side of the trail, while leaving the fragment on the left to naturally regenerate. Today, both sides look similar to the untrained eye. Both are green. Both look like they have trees and shrubs. But while they may look similar, Vijay’s recorders picked up several differences in their sounds.

VR: We found differences even at short distances. Most importantly, we got bird species that were not found in the other patch, which was encouraging that birds are actively starting to use these actively restored patches.

SD: The differences can be heard in the recorders that were recording simultaneously in the two fragments. One at the actively restored site….

[Sound from the actively restored site plays]

One at the naturally regenerating site.

[Sound from the naturally regenerating site plays]

SD: Have you seen other wildlife going through these patches?

VR: I’ve mostly seen larger birds like great hornbills, Malabar grey hornbills, even in this patch. They stop over, probably feed on some fruiting tree and fly further.

SD: The tea estates on either side are quite large.

VR: Yes, so expansive.

SD: And then you have these tiny, tiny patches.

VR: But it’s amazing that tiny patches like these, the animals are starting to use.

KC: Bioacoustics can be a powerful tool to monitor if restoration is working. To understand if wildlife is responding to all your efforts. And if the money you’ve spent on restoration has been worthwhile. Vijay’s colleague Pooja Choksi has done a similar study around Kanha National Park in Madhya Pradesh. Mongabay has written about it, and you can find a link to the article in the shownotes.

SD: Sounds are excellent. But I think nothing beats the joy of visiting the forests that you have planted with your own hands, and seeing animals return to them.

SR: The Matha Junction site that you just visited, it didn’t have giant squirrels. It didn’t have Nilgiri langurs.

SD: That’s Shankar Raman again.

SR: Now giant squirrels and Nilgiri langurs are coming there. Lion tail macaques are visiting. It’s a small fragment. So, they’re not there all the time. They visit and go. Great hornbills come, Malabar grey hornbills will come. Mouse deer are there. So, this is a visible change, because it was a site that simply didn’t have these. It was very degraded, a lot of lantana, open patches, things like that. And now you have all these rainforest birds that have come in 22 years. So, yeah.

SD: And how does it make you feel?

SR: It makes us feel good, yeah. Especially to see, you know, they’re probably now feeding on fruits of trees that we planted.

SD: Fruits of your labour.

SR: Ya, fruits of our labour.

Another nice thing is that some of these changes happen in fairly short period of time.

KC: Shorter timescales of just 10-15 years.

SR: Otherwise it’s quite a sobering thing to tell somebody that, look, the forest is destroyed. And if you want the rainforest back, you have to wait 300 years. Nobody’s going to feel like committing to it. But if you can see some effects in 10 years and so on. There are lots that can be done.

SD: They mentioned that you’re very good at imitating bird calls.

Let’s try a trogon. [Laughs]

[Shankar Raman tries a trogon call.]

KC: So, that was our story from Valparai. From the hills of Tamil Nadu, we’ll now move to the plains of north India. This time, to meet some towering personalities.

SD: But first, let’s announce the episode 2 quiz answers!

KC: Right. In episode 2, we played two calls, and asked you to guess the birds that produced them. Here are the answers. Call one.

[Call one plays]

This is a great hornbill.

Call two.

[Call two plays].

This is a Malabar whistling thrush or as it’s also called the whistling schoolboy.

The winners will be announced at the end of the episode. Now, back to the towering personalities.

Gopi Sundar (GS): I was travelling to Dehradun to give my exam and I saw it from the train. And it was quite amazing because I hadn’t seen a six-foot bird. And I used to think ostriches are the biggest ones, and India doesn’t have anything like that. But there you have them, you can see them from a speeding train.

SD: This is Gopi Sundar. He is a conservation biologist, and as he describes himself, a permanent student of nature. One towering personality that he’s studied and learned from for over 25 years is the sarus crane. That six-feet bird that he first spotted from a train. The sarus crane is a very unusual bird. And the first thing you notice about it is how incredibly tall it is.

SD: So, imagine something that’s about six-foot tall. It’s a very bright red head and completely grey and white otherwise. So if you don’t see the head, it looks like a very drab bird. The size, of course, you cannot miss. Male cranes are slightly bigger than females. And most of the male cranes were well taller than me.

SD: And how tall are you? Since you said that…

GS: Oh, I’m five, nine and a half.

KC: The sarus crane is, in fact, the tallest flying bird in the world. But it has one more very distinctive feature. And that’s why it’s in this episode. It’s call.

[Sarus crane calls]

GS: You really can’t miss the call. It is so loud and so in your face that you’re wondering what’s going on. It’s a blast. And so you can’t really miss a crane either visually or in terms of hearing it because it really lets you know that it’s there.

KC: And the bird is there in many places. You can find it in states like Uttar Pradesh, Haryana, Himachal Pradesh, Rajasthan and Gujarat, in India. But you can also find it in Australia and Southeast Asia.

Before we go deeper into sarus cranes, a disclaimer: Most of what researchers know about the sarus crane today is from studying their breeding populations, which is essentially a male and a female couple.

GS: The non-breeding ones are very young birds that have just left their parents’ home and joined these flocks and they live in flocks. And we know very little about the flocks and the non-breeding birds because it’s much easier to study the breeding birds because they don’t move away from the territories.

SD: And what are these territories? Well, the sarus crane is a wetland bird. It likes areas with water. But these wet areas can look very different in different places.

GS: If you go to Australia and Southeast Asia, you find these saruses inside jungles, inside eucalyptus forests in Australia and inside dipterocarp forests in Southeast Asia.

SD: But in India, these birds prefer to live, breed and nest in areas without trees. Without trees but with lots of water and dampness, like our agricultural fields. That’s where they have their territories.

GS: And the interesting thing about saruses and perhaps why they’re doing so well in India, is they eat everything that the farmers are growing.

KC: Almost everything like peas, ripening rice, wheat and potatoes. Gopi says that they love potatoes.

GS: So, I’ve seen saruses discover a potato field and demolish a part of it. It just digs it, smashes the potato in two, swallows two or three, goes to the water, drink some water, comes back, and then digs up some more potatoes. Just like us sitting on a sofa eating spuds while watching a cricket match.

KC: If an animal eats the food you are trying to grow, you might want to try and keep it away from your farm. You might even see it as a pest.

GS: Whereas our Indian farmers not just tolerate this kind of loss, which must be serious economic loss, but they, in fact, are very, very favourable to the cranes and they don’t allow outsiders to go and hurt cranes.

KC: In fact, a lot of wildlife in India live in agricultural fields.

GS: You will, of course, not find a tiger in rice fields, and you don’t want to find a tiger in rice fields. That causes different problems. But our rice fields are not bereft of species. They are full of species depending on where you are. Gujarat has different species because of the coastal and other areas. Uttar Pradesh is just like walking into a book for endangered species or even for common species. And then you have the Karnataka and Kerala farmlands where you have vast numbers of storks and herons and stuff. And so our fields and our human dominated areas are pretty exciting.

SD: Our farms and human-dominated areas are also very dynamic.

Imagine you’re a Sarus crane! Depending on which part of the country you are in, you could see new farms come in one day, and old ones disappear the next. One year there are new irrigation canals bringing more water in. Another year, drought dries up previously wet lands. Where there was potato growing a few years back, now there’s sugarcane. Suddenly there are roads where there were none before. And electric lines appear almost overnight in your flight path.

KC: Gopi says that the sarus crane has learnt to adapt to these constant changes. And if you listen closely, like Gopi and his colleague Suhridam Roy have, you can sometimes hear these adaptations in the crane’s calls. They know this because Gopi has observed thousands of sarus crane calls in his career. Suhridam and Gopi have also been analysing the calls of nearly 150 crane pairs.

GS: So, cranes are extremely vocal. Like all birds, they don’t like physical contact because birds have hollow bones. And so if they have physical contact, then the chances of serious injury is very high. So, because of that not only do they have a whole bunch of visual cues, they’ve also developed a fairly nice repertoire of acoustic clues.

KC: For example, when the sarus crane flies, it produces what is called its flight call.

GS: And it seems to be a way to tell other cranes around and also each other that we are flying, ‘where I am’, so that they can adjust the flight path and take turns together and so on. And also tell the other cranes that,  “We are here, this is our area and this airspace is ours.”

SD: Sometimes, new infrastructure can appear in your flight path. Like electric power lines. In fact, electric wires can be deadly for many birds, especially big ones like the sarus crane. This is because they’re large birds flying at 50-60km per hour. So, when electric lines suddenly appear in their flight path, it’s hard for them to take quick turns and avoid them. In some places, Gopi has observed something rather odd.

GS: In some areas where they’ve lived with human beings for a very long time, we’ve observed a very interesting call, which is a sort of a loud prrr but with a warble, I can’t really do it. And that call seems to warn a young bird, which has just begun to fly that there are electricity wires coming up.

And as a consequence, what happens is the whole family either flies higher or goes lower, and they avoid hitting the wires. Who would have thunk that they would have figured that out to be something as important to develop a whole new communication system?

KC: Gopi hasn’t analysed these modified flight calls yet. But he has heard them in Uttar Pradesh, where the cranes have lived with electric lines for a long time. In other places, though, he hasn’t heard it yet.

GS: For example, we haven’t seen that in Gujarat. We haven’t seen that in Himachal. We haven’t heard that in Australia because those areas don’t have electricity wires that much and they don’t have that high density of cranes that much.

KC: When it comes to the crane’s flight calls, Gopi has observed another modification in some places — this one maybe related to peoples’ behaviour.

GS: So in Haryana and Gujarat, for example, the cranes are very quiet when they fly. If you go to Uttar Pradesh, and if you go to Maharashtra and other places, they’re fairly vocal. And it’s sort of an indication that there’s probably some hunting there. And this hunting, we don’t know who does it. Maybe the privileged class go there and do regular hunting routes. And that has been seen in Gujarat and Rajasthan. In UP, you do have tribes that go out in the night and in the morning so that they don’t bump into villagers when they’re doing their stuff. But it doesn’t seem to be very high enough for them to not call. So, just by observing the cranes, you can make out how the people of the area are.

SD: Now, let’s look at one more call: one that the sarus crane is particularly known for.

[Two sarus cranes calls]

GS: So that is a very classical duet and there are very few birds that do something called a duet, because it takes two individuals to coordinate with each other and to produce a sound which sounds like one.

SD: The breeding couple’s duet, also called its unison call, has a set sequence, Gopi says. Like a well thought out piece of classical symphony. So, whether you are a sarus crane in the forests of Australia or Southeast Asia, or in the rice fields of India, the basic structure of a duet remains identical.

KC: But one thing that Suhridam and Gopi have found is that while the basic duet structure remains consistent across sarus crane couples, each pair has a unique unison call, like its thumbprint. And again, researchers know this mostly by visualising the calls on a spectrogram.

GS: Some cranes we can make out because the older cranes have a very deep throbbing call and young ones have a much shriller call. Those you can make out, but they have to be really extreme for you to make out differences. But if you look at the spectrograms and see how they pan out in terms of a graph, each one is distinct.

KC: This finding, Gopi says, could help us follow sarus crane pairs as they move and adapt to their changing environment.

GS: Let’s say there’s a road construction project and you don’t know where the pair went and you don’t have any markings on the bird or you haven’t put bands on the bird. Now, we can use unison call recordings, which is a non-invasive process. We don’t really have to touch the bird at all. And we can use that to figure out, which was the pair that we recorded five years ago.

SD: So, a duet sounds nice. I imagine a male and a female crane coming together like in the movies, a hero and a heroine meeting for the first time, and diving into a beautiful, highly coordinated duet. But sadly, it doesn’t work that way. For a male and female crane who have just met, their initial attempts can be, well, silly.

GS: They’re singing completely off tune and then the one of the birds just suddenly stops and stares at the other bird and then the other bird just stops and stares and suddenly starts calling again. They’re extremely awkward. So, they’re like two children just trying to get along for the first time or like a dance competition in a school, the first few rounds of the dance competition where everybody’s bumping into each other. It’s exactly like that. They’re very awkward.

KC: But the more time they spend together practising, the better they get at it. In fact, Suhridam and Gopi have found that the coordination of a duet, doesn’t just depend on how long a couple has been together. There’s something else.

GS: There are coordination indices that tell us how overlapping the calls are. If the calls are more overlapping than the coordination index tells us that they’re much higher coordination.

SD: This is where it gets interesting. In areas like Uttar Pradesh, where crane density is high, Suhridam and Gopi have observed that many crane couples have highly coordinated duets, whereas in areas like Haryana where crane density is low, the coordination is low.

GS: So, it looks like one of the pressures of having high density seems to be manifesting itself in the unison call, which is higher the density, the more they have to fight for the territory, vocally, not physically. And it seems like one of the ways in which they can present themselves as owners seems to be by giving more coordinated calls.

SD: So, a good area = higher density of sarus cranes = highly coordinated duets. In short, the coordination of a duet seems to be a response to the place where the birds live.

KC: In fact, the sarus cranes in India have been showing another peculiar adaptation in response to their habitats. For a long time, people thought sarus cranes only lived in breeding pairs. So, two birds within a territory. But since 1999, Gopi has observed some odd-looking sarus families — three birds instead of two. Trios instead of duos.

GS: We found three adults and they were taking care of the chick together. And that is highly unusual in a species which has developed to be so strongly territorial. So the entire being of the species, is to keep out the other cranes. When you see three adults working together to feed a chick like in a taxa like cranes, that is incredibly odd. Very, very odd.

KC: When his team started observing these trios more closely, they noticed something even more confounding. Just like a breeding couple sings together, these trios were also singing together.

[Three sarus cranes call in coordination]

GS: So, when two do it, it’s a duet. So I came up with the term, if three do it, it’s triet. And so these are three birds that are calling together and we found that triets are strangely enough, not that rare. It is not a one off. In fact, we found them in practically all the places where we are. And that’s pretty odd. Why is a crane that is evolved to be territorial, why is it allowing this third thing in it?

KC: Once again, the clue lays in the kind of habitat. They found that a couple allows a third bird to come and join them when the territory quality is very low.

GS: Meaning, the food availability is very low and they need more hands, more eyes or more beaks in this case.

KC: The chick grows from a hatchling to a 6-feet giant bird in just about two months. So, basically, the couple hires a nanny to help gather more food.

GS: What we see is like, even in a high density area like Etawah, there are territories which are high quality, and there are territories which are low quality. So we’ve only seen trios in low quality, even in a place like Etawah, which has the highest density of cranes.

Having said that, most of the triets we’ve seen are in areas like Haryana, Gujarat, where overall the territory quality is lower. So, this seems to be a behaviour that they have adapted to, to make sure that their breeding success goes up, while their surroundings are declining in quality.

SD: In short, unison calls, whether they are coordinated or not, and whether they are duets or triets – all of this give us important clues about the habitat in which the birds live. And that can be very useful for conservation.

GS: Conservation is always limited by money. And you want to go around a place and you find a place where the coordination is very low. That’s the place which requires conservation assistance because that’s likely to have the lowest density of cranes. So, it has immediate management and planning capabilities that you can do with acoustics with fairly reduced periods of time. You don’t have to spend five years in the field.

SD: As for the sarus cranes themselves, these birds are ancient. They’ve been a part of our myths and mythologies. They’ve seen empires come and go. But despite all the changes we’ve made to their environment, these birds seem to be doing okay.

GS: So, they’re able to do enormous behavioural changes, because that the world is going to change, that’s the reality. We are not going to be able to stop climate change and stuff because those are large scale patterns…But the saruses are now figuring out how they can assist themselves. Just because of their adaptation and also their behaviour, what we call as behavioural plasticity, seems like it’s a species that will outlast most of the species, maybe even human beings.

SD: So, any final parting thoughts?

GS: No, nothing from my side. Thank you for having me.

SD: Thank you so much.

GS: Oh! Yes Photo.

SD: Yes, a photo with Kartik.

GS: Yes. He has to be there.

[Everyone laughs and takes a picture]

KC: Over the course of reporting for these three episodes, we discovered that listening can be powerful. Bioacoustics can help not only in finding species but also in understanding how they live their lives, on their own and around humans.

SD: Of course, bioacoustics is helpful now, because researchers like Gopi, Shankar Raman, Divya and so many others have spent decades in the field, physically collecting data and observing wildlife. It’s these years of understanding that new technologies like bioacoustics piggyback on.

KC: All the researchers we interviewed agreed on one thing — While we are still in the early days of bioacoustics in India, it seems quite promising. As we have said previously, being able to listen and understand animal sounds has opened up a new dimension to our world.

SD: With that, we have come to the end of this mini-series.

KC: There’s one last thing to do. The episode 2 quiz winners! Aravind Aathi and Shatabdi Chakrabarti got both calls right. Congratulations, you win the “Best Listener” award.

For now, it’s goodbye. If you enjoyed the series, please share it with your friends and family, and write to us if you have thoughts or stories to share about sounds from the animal world.

Until next time. I’m Kartik Chandramouli.

SD: And I’m Shreya Dasgupta. And this has been Wild Frequencies.

Abhijit Shylanath (AS): This podcast is presented by Mongabay India. This episode was reported and written by Shreya Dasgupta, who’s a newswire editor at Mongabay, and Kartik Chandramouli, Mongabay-India’s senior digital editor. I’m Abhijit Shylanath. I did the sound design, mixing and editing, and original music for the series. This episode featured TR Shankar Raman, Divya Mudappa, Vijay Ramesh, Priyanka Hariharan and Gopi Sundar.

Many of the clips we’ve used for the Valparai section were thanks to Vijay Ramesh at the K. Lisa Yang Center for Conservation Bioacoustics Cornell Lab of Ornithology, and Project Dhvani, Meghana Srivathsa, Akshay Anand, Shankar Raman and Divya Mudappa.

Thanks also to Suhridam Roy for providing us with clips of sarus crane calls. Episode artwork by Hitesh Sonar.