Indian scientists are pushing boundaries in studying animal behaviour and communication leading to a better understanding of how observing the natural world can teach us how to conduct our own lives. India's rich biodiversity is a fertile ground for such cutting edge research. Finding solutions for today's problems is a big driver of soft power. India would do well to project her accomplishments in this field.
CSP spoke to Dr Rohini Balakrishnan, Professor at the Centre for Ecological Sciences at the Indian Institute of Science, Bangalore whose research aims at studying animal communication using sounds and various aspects around this broad umbrella. Recently, a newly discovered species of tree cricket in Mexico was named after her. The species was named Oecanthus rohiniae. She said, “I was extremely elated; it is the best honour a biologist can get!”
This new species from Mexico was described by an orthopterist Nancy Collins, based in North America, in collaboration with researchers in Mexico. Dr Balakrishnan hadn’t worked with them prior to this. Collins in another interview was in awe of the professor and said that when people come across this species, it will open their world to Dr Balakrishnan’s study.
Dr. Balakrishnan strongly believes that India is a great hub for not only those who are interested in ecology and evolution, but our rich biodiversity also constitutes an invaluable wealth in terms of diverse solutions to technological and medical problems, solutions that we are not even aware of today.
Dr Rohini researching crickets
What fascinated you about tree crickets that made you delve into their research?
Many aspects of their life and behaviour are fascinating for anyone interested in acoustics and communication. First, they are small insects that produce extremely low-frequency sounds (2-3 kHz, with wavelengths several times their body size). Producing such low frequency sounds is quite a feat for a small insect. In addition, these sounds are tonal, that is, like one pure song note, called the carrier frequency, and this changes with temperature! In fact, these have been called ‘thermometer crickets’ for over a hundred years now.
Second, some males manufacture sound amplifiers out of leaves by chewing a hole of the right size through them and use it to amplify their sounds: they are among the few insects who make such acoustic tools. We have studied how these insects choose leaves to build amplifiers, and who builds them, and found that males that are less preferred by females, such as smaller and less loud ones, are more likely to make these amplifiers.
“Studying biodiversity can inspire novel algorithms, devices, materials and therapeutic drugs, in addition to furthering our understanding of basic biological processes. Unfortunately, this aspect is largely ignored by our technocrats, administrators and politicians, who often consider biodiversity conservation to be at odds with economic development.
– Dr Rohini Balakrishnan”
Can you give us a birds eye view into your research and its significance?
Broadly, I am interested in animal communication using sounds, and I examine several aspects of this: how sounds of different types are produced, how they transmit in natural environments and what they mean to animals. I have been particularly interested in communication in complex, noisy environments: how private communication can happen in a cacophony.
The problems are analogous to communication using cell phone networks: individual people want to send private messages to each other but everyone has to put their messages out into the same public medium, often at the same time. Messages can get distorted or intercepted enroute, yet private communication is possible! Similarly, I examine what strategies senders and receivers in natural, non-human acoustic communities use to communicate effectively and avoid/outdo eavesdropping predators or competitors. I am also interested in why signals look the way they do: why one kind of signal structure and not another? This is often due to a mix of factors, including avoiding acoustic interference, transmission properties, avoiding predators or confusion with species having similar calls.
Over the years that you have worked with tree crickets, what has been your biggest finding and why?
I think our most significant finding working with tree crickets was that males, who call to attract females as mates, and females, who are silent and approach calling males, are at almost equal, and low, risk of predation. There are two reasons that these are important findings: first, although everyone believes that predation is a huge force of natural selection, with disproportionately high attention given to it in natural history documentaries, there are very few studies that have quantified the probability of predation in any system, as we did. Second, it has always been believed that males, who make these loud, conspicuous calls, are at higher risk of predation than silent females, but we found that this is not the case.
Can you tell us about some interesting collaborations you have had with scientists across the world?
One of the interesting projects we did, in collaboration with biophysicists at the University of Bristol, was to find out how the shift in frequency of tree cricket song with temperature happens and how females, who use this frequency to find males of their species, cope with this shift with temperature. Some very interesting observations emerged, such as that they are capable of changing the frequency tuning of their eardrums with temperature and loudness of the sounds. I also collaborated with them to perform 3-D reconstructions of insect ears using micro-CT scans as well as to understand how effectively leaves could be used as amplifiers by tree crickets. We found that tree crickets optimise the sound amplification from leaves by choosing larger leaves, making holes that match their wing size exactly at positions closer to the middle of the leaf. How they manage to measure the leaf size or hole size is still a mystery!
I have also collaborated with the Museum of Natural History in Paris, which has an extensive collection of cricket specimens from across the world, to try and identify the cricket species we have worked on in India, and to explore the use of song, which is specific to each cricket species, as a means of reliably identifying them in the field using sound recordings alone.
Considering the fact that crickets, katydids, mole crickets produce song-like sounds, has collaborative research been conducted with musicians? Can you give us an insight to that?
That is a very exciting area of synergy between the science we do and the arts! I would love to do more of this but have actively collaborated on two occasions. In one project, there were two German philosophers experimenting with using cricket sounds as part of cultural soundscapes, and we had an online 'cricket concert' (some years ago, before COVID!), where the sounds of live crickets from our lab were beamed live to online audiences. I have also heard of cricket concerts in Stockholm where the theatre is just filled with large numbers of crickets in cages, and their singing constitutes the 'concert.'
I also collaborated with A J Mithra, a musician in Chennai, and India's first zoomusicologist, (http://indiasendangered.com/interview-a-j-mithra-making-music-with-animal-calls/), who used the calls of rain forest crickets that we recorded and made an interesting musical composition. Very tragically, he passed away before we could carry this effort further.
https://soundcloud.com/aparna-sridhar-427495319/howzaatan-insect-symphony
Interestingly, in China and Japan, crickets have been popular pets and cultural icons through the ages (at least known from the 7th century AD) , and there are all kinds of interesting artifacts, such as decorative cricket cages made of clay, metal or vegetables (gourds), paintings and woodcuts from China. There were, in earlier times, even expert traditional cricket wing tuners, who could fix the pitch of your pet cricket's song by carefully applying tiny wax droplets at the correct places on the wing! The Japanese kept singing tree crickets as pets and they have often inspired haiku.
Oecanthus henryi, a type of cricket, uses leaves to amplify its calls to attract mates, a practice called “baffling.”
Are tree crickets used as an inspiration for biomimicry?
Although tree crickets have not yet been used to make biomimetic devices, they could well be. The findings above, of changing the carrier frequency of signals, producing loud, low-frequency sounds from very small emitters certainly provide novel insights that could be used to manufacture tiny loudspeakers. Indeed, in a separate collaborative project with mechanical engineers interested in nanotechnology and making MEMS speakers, we have figured out how field crickets produce their very loud sounds. This knowledge is being used to develop much smaller speakers than are available today, which could perhaps someday end up in your cell phones! Insect ears too are remarkable sensors: different species have ears that can act as mechanical frequency filters, or even change their tuning, as in the case of tree crickets. There are many important biophysical principles to be learned from studying insect and cricket hearing, with several possible applications in making miniature speakers and hearing aids, and some of these are being actively explored.
What kind of conservation projects on tree crickets are being conducted in and outside India? Are there any differences that you can spot in the strategies?
In general, tree crickets are globally widespread and quite common, and not usually the focus of specific conservation strategies. They adapt quite readily to human disturbance of habitats and seem to be able to jump from one plant host species to another, which improves their chances of survival. That said, there are few studies that focus on figuring out whether their numbers are in decline. Insect numbers and diversity in general are in decline as a result of human land use practices and climate change, as indicated by global long-term monitoring.
How can your research in animal communications and acoustics help in studying diversity and in conservation?
Given the current biodiversity crisis, it is imperative that we have rapid, non-invasive ways of monitoring our biodiversity, which provide us a window into the health of ecosystems. Animals such as crickets, cicadas, frogs, birds and mammals can often be recognised by their sounds, even if they are difficult to spot visually. We can put out passive recorders and examining these sound recordings or soundscapes to quickly assess the status of particular species, or groups such as frogs, birds or insects. Together with automated classification using AI, this could provide a rapid, reliable, non-invasive method of monitoring our biodiversity in diverse landscapes.
How does India compare in terms of technological advancement?
India has caught up quite a bit with other advanced economies in terms of general technological capabilities, but many of the specialised acoustic and telemetry equipment for our studies have still to be imported. Funding for such studies is not too hard to get in India since much of the research I carry out is very inexpensive, and the Indian Government does support basic research.
What is the most exciting part of observing cricket behaviour and communication?
The most exciting part of studying cricket behaviour and communication is the sheer joy of being able to work outside at night, listening in the dark to myriad sounds, focusing and absorbing each of them. One of my students rightly remarked it is almost like meditation!
On the other hand, working in the forest at night is also thrilling: one has to 'see' the world using sound, classifying the different sounds into familiar and unfamiliar, benign and possibly dangerous ones (such as elephants breaking branches) and plan one's own behaviour and movements accordingly. I find that very exciting. Every time I track a new call, there is the sheer joy of discovery that is hard to put into words.
Scientifically, crickets provide very tractable model systems where one can ask questions on morphology, physiology and behaviour, which can be addressed in the lab, but being the right size, also allow for detailed field studies of their behaviour and ecology. This allows one to move seamlessly across different levels of analysis, from physiology and behaviour to ecology and evolution. This advantage is available in very few systems: for example, Drosophila or fruit flies are great to work with in the lab, but one can learn very little about them in the field.
