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

Kartik Chandramouli (KC): You have tuned into Wild Frequencies, a brand new podcast mini-series brought to you by Mongabay-India.

Shreya Dasgupta (SD): This is a podcast where wildlife researchers from India share their stories of sounds from the animal world.

KC: And they decode those wild frequencies for us, one song, one howl and one chirp at a time! I’m Kartik Chandramouli.

SD: And I’m Shreya Dasgupta. This is Wild Frequencies.

KC: Every day, wherever you are – indoors or outside, there’s a lot coming at your senses.

SD: There are visuals to see, smells to smell, things to touch and feel, and sounds to hear.

KC: A lot of sounds.

SD: But many of us depend heavily on what we can see. Even wildlife researchers do. They count the animals they can spot, or they spend hours watching what the animals do, and how they behave.

KC: But most wild animals are not that easy to spot. Often they are hidden, camouflaged, or just not around when you are. Sometimes the animals are just too small or too far away to really carefully observe.

SD: Enter….. sound.

KC: Just like us humans, animals also communicate. They sing, they chirp, they whistle and trumpet.

SD: All this talking and chattering is ‘gold’ for researchers. Because even if the animals can’t be seen, they can often be heard. And if you listen carefully, their calls can tell you a whole lot. Starting with the simplest of questions: Who is around us?

KC: Let’s take the most obvious example and my personal favourite – birds! You tend to hear birds chirp and sing much more than you can actually see them. Especially if the birds are small and frisky, they are so hard to spot. Which is why, any birder–whether they’re an amateur or an expert bird researcher–will spend a lot of time trying to learn bird calls. It’s because every bird species has a distinct call that it makes. And once you learn to match a call to the bird….

KC in the background: That’s a coppersmith barbet!

KC: …Your bird identifying skills go from level 0 to 10.

SD: These sound-based IDing skills are super handy. Let’s say you’re a wildlife researcher and you want to understand the diversity of birds around you. If you only relied on what you can see, then you would have to wait around, strain your neck, and rush from one bush to another just to try and figure out – what is that bird? Does it have a black head? Are those blue cheeks? Is that a grey ring around its eyes? In fact, bird  calls can be so important that researchers have tried using them to find lost species. You know, species that haven’t been seen in ages, like in the case of Jerdon’s Courser.

KC: So, the Jerdon’s Courser is this small nocturnal ground-dwelling bird. It looks super cute. It’s a bird we know very little about. For a long time it was thought to be extinct. But in 1986, this one guy spotted it. People saw it a few times after that. But it’s still so rare, that it was last seen in 2008.

Now, here’s the interesting bit. One scientist P. Jeganathan, who works at the Nature Conservation Foundation, managed to record the bird’s calls around 2001.

Jerdon’s Courser’s call plays.

KC: What you just heard are the only known recordings of Jerdon’s Courser. Researchers have designed a system using these rare recording to listen for the bird. The hope is that it will one day detect a Jerdon’s Courser when it calls and says, “Hey, I’m still here!”

SD: Well, animals talk. And there’s an entire branch of science called bioacoustics, which is where researchers go about trying to decode these sounds that animals produce.

And one way this can be useful is to find and ID species that are around us. Like different birds of course. But it can also be useful for a whole range of other animals. Animals that are around you, but easy to miss.

Egyptian freetail bats fly around.

Rohit Chakravarti (RC): Okay, many Egyptian freetail bats flew very close to us Leading to this commotion. Oh, wow!

KC: I see around seven to eight Egyptian freetail bats.

RC: Correct! I’m Rohit Chakravarti. I’m a bat researcher.

SD: Like many budding wildlife enthusiasts, Rohit started off being interested in birds. But when he was considering options for his professional life, he switched to bats. We met him at the Indian Institute of Science or IISc in Bengaluru, where he mentors some students.

And we asked him why bats and not birds?

RC: Even though I liked birds a lot, I never took to studying them because, in order to study birds, I would have to be really good at it. But with bats, and the less amount of competition, I could do anything and it would turn out to be new. So, that was also quite a big motivation to study bats.

SD: So it was the lack of competition?

RC:  Correct. I’ve never considered myself extraordinary.

KC: Of course, he gave a more serious answer, as well. The fact that bats are not everybody’s most favourite animal, extremely vilified, but also critical for our environment. So, someone has to step up and study them. And now Rohit has become one of the few bat experts in India.

SD: And for bat experts like him, while being able to visually spot bats is great, that’s very hard to do. Bats fly at night, when visibility is poor. They’re often tiny, and flit about super fast. So good luck trying to figure out what species of bat it is only based on what it looks like. Which is why Rohit and other bat researchers identify bats using the sounds that the mammals produce.

KC: One of their calls, specifically – the echolocation calls.

SD: These are simple pulses of mostly very high frequency or ultrasonic sounds that bats produce to navigate the world around them. They call, and they listen for the echoes of their calls bouncing off things around them. This is how Rohit explains it.

RC: Imagine I am a bat and you are in front of me. I produce this ultrasound. The sound goes, hits you, and then comes back. Now, when it’s going towards you, some of the sound is getting absorbed by your skin. Some of the sound is coming back to me. So, in a fraction of a second in milliseconds in my full speed of flying, I’m making these calculations in my head about how much sound I emitted, how much sound came back to me, how much delay there was in the sound coming back to me and so on, to tell whether you are an object, whether you are another animal, whether you’re edible or not. All of these decisions I’m making in my head in a fraction of a second… So, that’s what bats are doing in the night sky. They’re using these sounds to find their way and also to catch insects in the night sky.

KC: But do you remember, he said that fruit bats like the big flying foxes we see in our cities – those don’t echolocate.

SD: Yes, I didn’t know that. So I went back and read up on bats, and this is what I learned: Bats have been put into these two broad groups, microbats and megabats. Microbats tend to be small and insect-eating, and include the bulk of bat species. And these bats echolocate. Megabats, or fruit eating and nectar drinking bats, tend to be larger, and have decent eyesight and smelling abilities. So, they either don’t echolocate, or do it rather inefficienty. Because I guess you don’t really need to throw ultrasonic pulses at a fruit. You can just see and smell it.

KC: So, this listening to ultrasound pulses is generally useful to identify the insect-eating species.

SD: And it doesn’t even matter that the sounds are hard for a human to hear. Because researchers have a tool that can listen to bat ultrasound and show it to us as a graph. Sound to visuals. This device is very creatively named A Bat Detector!

Rohit opens his bag to pull out the bat detector.

RC: So, my bat detector looks like a tablet. It’s in fact based upon a tablet. The sound comes in through the ultrasonic microphone. So, if a bat is around, it will call, and the call will go through the ultrasonic microphone and it will be displayed on the screen in the form of a graph, which is called a spectrogram. So, a spectrogram is frequency on the y-axis, time on the x-axis. As time moves by, you see the bat call on the screen…once you see that call on your screen, you know that there’s a bat around.

SD: The graph that gets displayed on the screen not only tells you that there’s a bat around, but also, what kind of bat.

KC: Now, there are around 20 families of bats in the world and nine in India. And by family, we mean the taxonomic hierarchy family, not our one big happy family.

For example Canidae… is a family of dog-like animals such as wolves or foxes, and felidae… is a family of cat-like animals such as tigers and leopards.In the same way, bats with similar features have been grouped under different families.

SD: And just like all species of canids kind of look like variations of dogs, all species within a bat family produce similar-looking, echolocation calls. But like dogs clearly look different from cats, the calls of two bat families sound very different from each other.

RC: So, the most common species that we have in our neighbourhoods in most parts of India, there’s a family called evening bats. These are rather simple looking mouse like bat ..What we call pipistrelles.

SD: The bat calls you’re going to hear now are 5-11 times pitched down, so that they become audible for humans. You can also see the spectrograms in the transcript. The link is in the shownotes.

RC: Pipistrelle calls are actually exactly like a hockey stick.

Pipistrelle call plays.

RC: When you compare that to the call of a leafnose bat, which is a family that’s quite common around Bangalore, their calls are the exact mirror image of a pipistrelle’s call.

Leafnose bat call plays.

RC: A horseshoe bat, on the other hand… Horseshoe bats, they’re called so because, you know, they have this horseshoe-like structure at the base of their nose. They’re leaving sound out through their nostrils rather than their mouth, which means that, you know, they’re essentially speaking out of a loudspeaker. So, the calls become like a thin whistle, a straight whistle with, uh, dips in the front and dips at the end.

Horseshoe bat call plays.

SD: So, nine families isn’t that much. Have you memorised all their signatures?

RC: I’ve had to. Otherwise I wouldn’t be called to give gyaan on Mongabay.

KC: Okay. So let me recap. When you point a bat detector to the sky and a bat passes by, you see its signature call shape on your screen. Let’s say, you see a hockey stick. That tells you that the call belongs to the pipistrelle family. The next step is to ID the species. And for that, Rohit says, you have to look deeper at the graph.

RC: On the first instant, you are only looking at the structure, then you actually start reading the graph and look for the frequency at which the bat is calling. So, to give you an example, two different species of pipistrelles that occur in Bangalore – The Kelaart’s pipistrelle, which is slightly larger, And by large, I mean eight grams, which is smaller than your travel toothpaste tube. The Kelaart’s pipistrelle calls at about 35 kilohertz. The other species is called the Indian pygmy bat or the least pipistrelle, which is smaller; it weighs four grams or six grams, and calls at about 50, 51 kilohertz. In horseshoe bats actually, these differences are even more well-marked. The largest species of horseshoe bats can call at about 30, 40 kilohertz, whereas the smaller species can go as high as 110, 120 kilohertz.

SD: You know, it doesn’t sound that hard. Memorise some call signatures, and remember some frequencies. But I guess that’s the point – making bat identification and detection easy in real time. But all this knowledge of what call belongs to which bat family and species, that has been painstakingly built. In fact, scientists around the world, including people like Rohit, spend months in the wild, literally catching bats, identifying them while in hand, and then recording their calls.

RC: Later on, when somebody is working in that area, they don’t need to go through the entire process of catching (the bats). You already have a library of bat calls. So, that’s something I did in the summers of 2016 and 2017 in the Himalayas, in Uttarakhand. Other colleagues have gone out and recorded bats in the Southern Western Ghats, in the Northern Western Ghats, and in the Andaman Islands. So broadly, with the effort of a few different colleagues, we know the calls of at least 60 to 65 species of bats in India, which is about 45-50 percent of our diversity.

KC: In fact, Rohit is the founder of the Indian Bat Call Library, which is this huge collection of bat calls. There’s a link in the show notes.

SD: Many of the calls in this database come from Uttarakhand, where he did his PhD. And he had one very interesting incident to share.

RC: My favourite recording site ever has been this one place where I did my PhD fieldwork in Kedarnath Wildlife Sanctuary.The lowest elevation site is a small village called Mandal. The neighbouring village had a small playground where kids played cricket during the day, nestled in the middle of different hills. And there’s a small forest area right next to the cricket ground. So, we placed our bat detector at the edge of the forest and the cricket ground, so that we could record bats both from the forest and from the cricket ground. And in two nights of putting that bat detector out there, and recording bats for 10 hours every night in summers, we got a total of 14 species! And that was massive. I have never recorded so many species with one stationary bat detector placed for 20 hours at one spot. That simply blew my mind.

SD: We were not that lucky at IISc, but I must say, we had our own bat bonanza.

Podcast hosts walk around at the IISc campus.

SD: Just a disclaimer: You’ll hear the bat detector go off and produce different sounds. These are not actual bat calls, but a version of it produced by the detector itself, a recreation let’s say, for the human ears.

RC: So, an Indian pygmy bat, or the least pipistrelle, the smallest species that we have in Bangalore. just probably zipped past.

SD: (Pointing at a building on the walk) That’s a very British-looking building.

RC: Yeah, and that’s why we are here to look for the Egyptian free tailed bats, which happen to, for some reason, like British architecture a lot. They seem to have more of a colonial hangover than most Indian middle class.

Sound playing from the bat detector.

RC: This is a smaller species, calling at about 40 kilohertz. Okay, that’s interesting.

KC: Was that a pipistrelle?

RC: Correct. So I’m guessing this is the Indian pipistrelle…Whereas the one calling at above 50 kilohertz was a least pipistrelle, the Indian pygmy bat.

RC: So, the free tailed bats are back, but this time they are a little higher. Okay. Now they are within our hearing range. Okay, so that’s a small bat calling at about 38 kHz. This is the Kelaart’s pipistrelle.

Egyptian free tailed bats fly.

RC: Many Egyptian freetail bats flew very close to us.

Leafnose bat calls.

RC: That was a very typical leafnose bat call.

KC: I think my first bat-watching experience was great! Six bat species within an hour.

SD: Same. I’ve not seen so many bat species around me. And all thanks to bat detectors.

SD: What would we have not known, if we didn’t have detectors?

RC: Most basic, we wouldn’t know how many species of bats there are in Bangalore. In fact, in our immediate surroundings too. Without a bat detector, all I knew was there is a small bat, uh, flying over my head in Bangalore. There is a medium-sized bat that I see feeding on Singapore cherry trees in Bangalore. And there is a massive bat that you find all over the country. When I had a bat detector, I realised that the small bat flying over my head is actually three different species.

KC: Basically, good sound recorders have helped researchers unlock a new dimension to our world. A whole new way of understanding what’s around us. Whether that’s on land or underwater, which is what we will hear in the next segment.

Isha Bopardikar (IB): Initially when I used to look at the sea, I used to think that ‘oh, it’s very calm.’ But then when you put down a recorder, there’s this whole world underneath that you can hear.

KC: Sometime in April 2024, I met up with Isha Bopardikar, a marine biologist who lives in Mumbai and works along the Maharashtra coast.

SD: To be specific, she studies marine cetaceans, like whales, dolphins and porpoises.

KC: And like Rohit, Isha uses acoustics to study these marine mammals that are often close to the shore. So, we got chatting in a small recording studio, just five kilometres from the beach.

KC: How does a marine biologist usually study these species underwater? 

IB: So usually, for marine mammals studies, you do vessel based surveys where you go out on a boat, and you look out for these animals or any signs of their presence. If you’re adding a behavioural component, then you usually do focus sampling, you look for a group, you stop the boat, you take down all your measurements, you will look at their group size, composition, how many calves that are there on mother calf pairs, how big the group is. Are they foraging? Are they feeding? Are they travelling? Are they socialising?

So it depends on the question, but a lot of it is the visual data.

SD: But getting all this visual data must be challenging. Because well, the animals are mostly underwater.

KC: It’s particularly difficult along our coastline because Indian coastal waters are often murky and turbid. And here… sound is a powerful tool.

IB: It’s very powerful underwater because there’s so little that you can see. And a lot of these marine animals use sound as their primary mode of communication, right from fish to baleen whales, and even the shrimp like they use sound… vibrational motion. So it’s very important underwater.

KC: In fact, water makes seeing things, and smelling things quite difficult. But sound… Sound travels four times faster in water than air. So, marine mammals use sound a lot. They use it to communicate, to find mates, and to navigate the vast ocean. Many decades ago, marine researchers figured out that they could record all these sounds and maybe understand these animals a little bit better. Researchers have shown that humpback whales have these complex, soothing… sometimes haunting.

Whale sound plays.

SD: Or that dolphins communicate with each other through whistles.

Dolphin whistle plays.

KC: Just like these researchers, Isha also records and listens to the calls of marine mammals along the west coast of India. Two species to be specific – the Indian ocean humpback dolphin, and the finless porpoise.

IB: The Indian Ocean humpback dolphin (Sousa plumbea)…They are found in very shallow waters. They have a habitat preference for coastal and estuarine areas. You will usually find them in depths of up to 30 to 40 metres of water. So, they’re very coastal. And that puts them right in the middle of all kinds of anthropogenic activity. This is where you have your busiest fishing lanes, shipping areas. There’s a lot of construction. There’s a lot of pollution going on in that area, There are chemicals, noise, all kinds of pollution.

SD: Similarly, the finless porpoise, which frankly, I didn’t know existed along Indian coasts, also lives a danger-filled life.

IB: They are very small, maybe four, four and a half feet long. They’re grey. So, they are the colour of the water… sometimes. They are round snouted. round teeth. They look really cute, actually. They are tiny animals and they don’t have any defense mechanisms. They’re usually very common in bycatch, because if they get caught, they just can’t really chew through the net. So, they have a tough life.

KC: So, both the Indian Ocean humpback dolphin and the finless porpoise face several threats. But they haven’t been studied enough, which makes their conservation difficult.

IB: Well for informing any kind of conservation action or policy, you first need a lot of information on the baseline data of a species like where these animals are, when they are present in an area, how many animals are present in an area. Then you can go to why they are present in those areas. But for us, we didn’t have any background information on these animals.

KC: To get some of these baseline data, Isha and her team began recording the sounds of dolphins and porpoises living along Maharashtra’s coast. The sounds helped them figure out where these animals were and the types of calls they made. But bioacoustics helped the team go a bit further. They found that certain sounds could actually help them count the animals. One particular sound in fact, called the echolocation click.

IB: They click, they wait for the echo to come back. And they get a sense of how their environment is. They use the same principle for finding food, for foraging and then for feeding.

SD: Which means they echolocate quite like bats then?

KC: Yes, it’s quite similar. And like in bats, dolphins and porpoises have their own unique echolocation clicks. Which means their clicks are at different frequencies.

To detect the echolocation clicks of bats, you use bat detectors. To record the clicks of dolphins and porpoises, researchers use a special microphone that can record underwater. It’s called a hydrophone. But that’s only step one. To count how many of these animals there are, Isha uses a more specific setup of these “hydrophones”.

IB: It’s called a towed array. So it’s got a series of hydrophones they are linear, they’re in one straight line. We have around four of them. And they’re all connected to an autonomous recording unit. And they’re all working at the same time…and It’s continuously towed behind the boat.

SD: Which, Isha says, means that the four hydrophones are like four independent observers moving behind them, continuously listening to the environment and recording everything.

IB: So when you tow it behind the boat, as you move along the line you if you cross an animal that’s vocalising, the sound that they produce reaches each of the hydrophones microphones at a slightly different time.

KC: And if you know the time that it takes for an individual’s clicks to reach different mics, you can triangulate where the vocalising animal might be located. You keep doing this repeatedly in a given area. Then, through a series of careful mathematical calculations, you can figure out how many total individuals might be around. This is actually an adaptation of a commonly used population estimation method called distance sampling. If all this is too technical, don’t worry about it.

SD: So basically, what Isha has done is use echolocation clicks as a proxy for a porpoise or dolphin’s presence.

KC: That’s right. Isha took some time to build the perfect recording setup, but this sound-based population survey seems to be working particularly well for the finless porpoise.

IB: So, they are producing these highly directional, high frequency narrowband sounds that you can localise and record very well if you have a particular system in place. So that’s what we had. And we got amazing recordings for finless porpoises, we were able to localise individuals using the array.

SD: And they are seeing some interesting trends.

IB: So for now, we’ve done a comparison between the acoustic and visual estimates for just encounter rates, And we realised that for finless porpoises, if we have 30 visual encounters, we have three times more acoustic encounters. A lot more acoustic detections than the visual. So, that was pretty cool. So there’s very little of these animals that we are seeing.

KC: But counting animals only based on their calls may not work for every marine species.

IB: I think we learned that with the humpback dolphins. We wanted to get densities for these animals, but not all of them vocalise at the same time. So, your difference between the acoustic group size and the visual group size is very different. Sometimes they’re like 20 animals but what you see on the acoustic data is only like two or three click trains. So, you always need a visual group count for the humpback dolphins. I would not rely only on the acoustic data.

KC: So, we’ve heard two things until now—sound can be used to find animals that are difficult to observe and it can also help count them, which brings us to our last segment. We will hear from someone who counts a rather elusive land animal that lives around many of us – all through sound.

SD: What’s the wolf howl portrayed in most pop culture?

Bilal Habib (BH): It’s a grey wolf. It’s a U. S./ Canadian wolf. It’s not our wolf. So, that’s one of the most interesting howl which people listen.

SD: This is Bilal Habib, a scientist at the Wildlife Institute of India. Bilal has been studying Indian wolves for over 22 years.

BH: I probably was the fourth student from India to do a PhD on wolf and just a couple of days ago, my fourth student defended a PhD on wolves.

SD: Full disclosure, I also worked with Bilal on my Master’s thesis project many, many years ago. Ok, now back to wolves. So, wolves are everywhere in our pop culture– movies, tattoos, and even books.

KC: The Jungle Book! I love the book and the cartoons. The main character, Mowgli, lives with this pack of wolves with names like Akela and Raksha. But from my conversations with friends and family, I realise that many people don’t know much about Indian wolves. That these animals exist in the Indian plains, in the hot countryside and in grasslands. And that they can literally be found around some of our villages, towns and even cities like Pune.

BH: So, it’s very easy to see a tiger and a lion in our country, but it’s very difficult to see a wolf in our country. Actually the people called it the ghost of the grasslands. It’s actually the ghost. And if you go to Tadoba, you go to Ranthambore, you go to Bandhavgarh, you will not see a wolf. And if you go just to the outskirts of Pune, you’ll see a wolf. So it’s actually a neighbour.

SD: It may be a neighbour but chances are that you still won’t actually see it. Because wolves are, as Bilal puts it, geniuses at staying hidden.

KC: For researchers, this is rather inconvenient. Because the Indian wolf is an endangered species, threatened because of two main things – One, because of where it likes to live, which is grasslands. And grasslands don’t stay grasslands for long because they make way for farms, industries and other things.

SD: And two, because of how it lives, alongside so many people. Also, these animals have very large home ranges, as vast as 230 square kilometres. That’s bigger than Kolkata.

KC: You might think we know everything about wolves. But because they are so good at staying hidden, we don’t know some of the basics. Like how many wolves do we even have in India?

BH: There was one publication somewhere in, I think 2000, which talked about the population of wolves in India. So, what they did is they, they actually identified the wolf habitat and then they identified how big a territory is. For example, if we have 50,000 square kilometres of wolf habitat in India. And if a wolf territory is 200 square kilometres, how many territories can be accommodated? Okay. So, that was a rough estimate of the wolf population in our country.

SD: But these older rough estimates are not reliable at all, Bilal says, which makes conservation of wolves difficult.

BH: I think it’s a species which is declining fast. And I think if somebody asks us, we may have a lesser number of wolves than tigers and lions in the country. They are far less. And if we don’t have numbers, we can’t think about conservation. So, we will be always blind whether we have 2,000 wolves, ..whether we have 3,000 wolves, whether we have 5,000 wolves. So we’ll never know. And if we are going to do some management interventions, say we are going to do something for wolf protection, if we don’t have numbers, how we are going to know that what we are doing is right or wrong. So, the numbers are actually a test of conservation and management success.

KC: So, don’t the conventional ways of estimating animal numbers on land, like using camera traps or collecting scat which is the same as poop, work for the wolves?

SD: Not really. And Bilal says that’s because you can’t identify individual wolves in camera traps images, like you can identify a tiger or a leopard. And you could technically look for wolf poop, but where do you even start, and how much area do you cover, when your animal has such a huge home range?

KC: I can see where this is going.

SD: Yes! Sound. Sound can once again come to the rescue. Wolf howls, in particular.

Wolf howls.

SD: Now, Bilal has studied wolves in multiple ways over the past two decades. He has physically watched wolf packs for hours. He has also collared several of them and tracked them through GPS. Somewhere along this journey, Bilal and his students also started recording wolf howls.

BH: So, wolves, they produce 12 different types of communication. Okay. So howl is one of communication, because it’s a long range. They use it when they have to communicate within the pack members. Because it goes, it goes up to kilometres, two kilometres, even in some areas it can go up to six kilometres.

KC: If you were six km away from the wolf, you wouldn’t hear its howl immediately. It would take about 18 seconds for the sound to reach you.

SD: Now, howls are very common across canids – wolves howl, dogs howl, coyotes howl. But are these howls the same or different? A bunch of researchers around the world, including Bilal, decided to compare them and find out.

KC: When the study came out in 2016, they found that every wolf species and subspecies has its own unique howl.

SD: Correct, they call it wolf dialect.

BH: So wolves of India, they howl. Yes. Wolves of the US, they also howl. The Canadian ones also howl, and other wolves also howl. But there’s something which we call dialects. So, like, for example, everybody speaks Hindi in India. But we speak different Hindi.

SD: How is the Indian wolf howl different from other wolves?

BH: So, if you see, our frequencies are far lower than the others. That makes sense also, because if you see wolves in the US, they live in a closed habitat. They live in forests. So, in forested ecosystems, you need a different frequency.

SD: A higher frequency or a higher pitch can help your sound move past all the trees and shrubs and obstacles in a forest and reach the intended ears.

BH: Whereas our wolves, they live in grasslands, grasslands are open. So even if we produce low sound, it will go far off. So, how habitat has influenced the evolution of the different frequencies, a different wavelength.

KC: All of this made him wonder: If howls are distinct to species, are they also distinct to every individual? And so Bilal and his students thought of a study. They first went to Jaipur Zoo.

BH: And in Jaipur Zoo, we were having the known wolves. So we put a camera and then we put a recorder. So we were actually knowing which individual is howling. And we were recording that particular individual and we had a howl. So, Jaipur had something around five-six individuals. So we did this for four to five days. So, we recorded the different howls of these individuals.

SD: When they analysed these howls, they did see what Bilal had suspected: each zoo individual had a distinct howl.

BH: So that was like, that was the first thing, okay, yes, uh, in a controlled experiment it can be done. But if we take it to the wild, what’s going to happen?

KC: So, they started recording the howls of wolves in the wild.

SD: And the final analysis confirmed that yes, whether it’s a wolf in a zoo or a wolf that lurks around farms in Maharashtra, individuals seem to have unique howls. This is the first published study, Bilal says, to find something like this in wolves.

BH: So the take home was, yes, now if you can identify individuals, it opens a lot of other things which you can do. Now, it’s like a stripe pattern of a tiger. It’s like a unique pattern associated with an individual. So, when you have something unique associated with an individual, then all other population estimation techniques and all other things become applicable.

SD: One method in particular. It’s called capture-recapture. If you can identify individuals in some way – either because they have unique stripe patterns like in tigers or because they have unique howls, like for wolves – you can count them easily. You go out in the wild, and put up cameras or recorders in different places. These cameras or recorders will capture photos or howls of some individuals in the population, but they will also miss several who don’t cross their paths. You keep doing this, one day, then another. And you can eventually figure out how many total individuals might be out there.

BH: We have already done this in Maharashtra. So, now I am looking for the second stage, to replicate this across the country. Maharashtra, I think, will be done in a couple of months. It’s already in the final stage.

SD: At the time of recording this episode, the results were not published yet.

KC: Since Bilal has listened to hundreds of wolf howls, we asked him to recreate it for us. And… he refused.

SD: Haha. So, we asked him why he loves wolves when so many others don’t.

BH: As an ordinary individual, you can’t love a wolf because there are so many tigers, lions, especially in a country where you have tigers, you know, leopards, leopards, clouded leopards, you have so much charisma. But only charisma is ecology. Only charisma is its geniusness. You know, which is the first animal which we domesticated? It’s not the tiger. It’s not a lion, it’s a wolf. We have around 900 varieties of dogs. And all these 900 varieties are an outcome of wolf. So, we love so many dogs. I think we should love the ancestors of the dogs.

KC: Who would have thought that one day researchers would be going out into the wild, with recorders in hand, identifying animals and even counting them, just using their sounds.

SD: It’s still initial days though, at least in India. Like Rohit mentioned that he basically wishes to have an army of people who go out there and record calls of all bat species in India under different scenarios and in different places..Bacially build a robust call library, and only then can you make realtime ID-ing truly seamless.

KC: Isha said something similar – that we have a very partial picture of all the different calls that marine mammals produce along our coasts. There’s a lot more to be seen… sorry, heard.

SD: One challenge is that the specialised recorders that allow researchers to record these animals are expensive. And there’s an initial steep learning curve for researchers.

KC: But if you can cross these barriers, you could find yourself seeing animals in a very different light. Maybe you can even begin to figure out, what are animals saying? And why?

SD: Well, researchers in India are already doing this – listening to animal calls to understand animal behaviour. You can learn more about this in the next episode. But don’t go anywhere yet. We have a quiz for you.

KC: It’s a very simple one. We’ll play two calls. And you have to guess what animals made those calls. Send your answers to kartik@mongabay.com. Okay, here you go.

Two animal calls play.

KC: Go back and listen to them again if you want to. And tune in to the next episode to see if you got it right.

SD: For now, this is it. If you enjoyed listening to this episode, please follow us wherever you get your podcasts. And rate us wherever you rate your podcasts. See you soon.

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. Editing, Music, and Sound design by Abhijit Shylanath. That’s me. Thanks to Rohit Chakravarty, Isha Bopardikar from IISER Tirupati, and Bilal Habib from Wildlife Institute of India for speaking with us, and for sharing their sound clips with us. Episode artwork is by Hitesh Sonar.