#AnimalSounds:Check out how Rohit Chakravarty is making bat calls audible
His Instagram page now features audio clips of other creatures too, and he’s betting you can’t tell what they are.Updated: Oct 11, 2020, 10:20 IST
It takes superpowers to hear a bat call. Unless you’ve tuned in to Rohit Chakravarty’s #animalsounds series on Instagram.
Chakravarty, 29, is a chiropterologist; a person who studies flying mammals or bats. He’s been researching the supersonic calls of bats in the Western Himalayas since 2016, and has created an audio library of the echolocation calls of 32 species of bat found there. (Across India, incidentally, there are an estimated 128 species of bat).
Since July, Chakravarty has been using a special filtering process to render the bat calls audible to humans. “It’s just my way, as a researcher, of de-stigmatising this animal that people have such an aversion to and have so many misconceptions about,” he says.
Chakravarty posts his rendered audio clips on Instagram (@paintedbat), with a picture of the species you’re listening to. The sounds are not what you’d expect. The greater yellow house bat, European free-tailed bat and the pipistrelle chirp like little birds. The call of the horseshoe bat (the one believed to have carried Covid-19 over to the human species) sounds like an electro-funk beat. The Himalayan leaf-nosed bat sounds like a motorbike failing to start.
“The bat library is not like a bird database, where you can just hear and identify different species,” says Chakravarty, who is pursuing a PhD at the Leibniz Institute for Zoo and Wildlife Research in Germany. “Essentially, you can never hear what the bat has to say. But you can bring its call to within hearing range.”
Chakravarty uses two methods to do this — time expansion, where he stretches the audio clip, thereby lowering its frequency; and heterodyning, where he feeds his recording into a software programme that produces audible outputs without slowing the recording down.
The recordings are made on a device he calls the ‘bat detector’, an ultrasound recorder that specialises in recording bat sounds. The audio data is typically used to try and tell what bats inhabit an area.
Chakravarty’s Instagram page also features the calls of other animals we’d almost certainly never otherwise hear. Like the gecko he shot while doing fieldwork in Thailand. “Its sound can travel up to a kilometre,” he says. Another recent post was a high-pitched scream that Chakravarty challenges his followers to identify. It turned out to be the call of a sambar fawn.
“There is a good database of bird calls in India, and of the frogs of the Western Ghats. But the rest of our wild soundscapes are largely undocumented,” says Chakravarty. “There is a lot to be learnt from animals’ alarm calls, mating calls, feeding calls, hunting calls. There is a lot left to learn about bats too. Are they bickering, defending territory, serenading a mate? Hopefully someday we’ll know.”
Bats by themselves are a misunderstood, little known and overlooked aspect of nature, says naturalist Sunjoy Monga. “Bats are secretive and have been in the bad books of humanity for a long time, and any incoming information on these nocturnal creatures, such as in Rohit’s social media project, is welcome.”