Now we can listen deeply to nature: hear the one about the plant triggered by the sound of a caterpillar?

A friend gave me a colourful birthday card when I was a teenager. On it was a resplendent peacock, delighted with himself as he fanned his iridescent tail feathers into a dish-like shape. As he waited for the offers to roll in from two onlooking brown peahens, they instead stared back at him, bored and unimpressed. The word bubble above their head read: “Cut the crap, and show us your willy”. The poor sod.

I was reminded of this card while reading the late Karen Bakker’s recent book The Sounds of Life: How Digital Technology Is Bringing Us Close to the World of Animals and Plants. It seems, all these years later, that we’ve been visually blindsided by the peacock’s beautiful plumage but missed what’s really going on: the peacock isn’t just showing off his impressive bits. He’s also talking to the peahen. In 2015, scientists discovered that peacocks produce infrasonic sounds – inaudible to the human ear – using their tail feathers at a frequency that vibrates the comb on the peahen’s head. This isn’t merely a visual performance; it’s also a sonic one.

Humans, particularly in the western world, have long believed that what we cannot hear doesn’t exist. But now scientists, using cutting-edge technologies, are undertaking what many indigenous people have long done: they are listening deeply to nature and realising that even silence, as we perceive it, is an illusion; it is, instead, merely the absence of sound audible to the human ear.

Nature’s soundscape never quietens. Bats, plants and insects emit high-frequently ultrasonic sounds, and whales make low-frequency infrasonic calls, as do elephants.

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Advances in technology – from tiny, portable field recorders to powerful computers using artificial intelligence that decode the patterns and meaning of the sounds – give us a chance to listen to and understand the myriad of sounds with fresh ears. A growing body of evidence shows that many species – not just humans – are vocally active and use sound to communicate.

According to Bakker, these technologies have given us a “planetary-scale hearing aid” that extends our sensory perception beyond our physical capabilities, bringing us into a new world of understanding.

Scientists are placing listening devices, such as digital recorders and drones, that can decipher frequencies inaudible to the human ear, in all parts of the world, from caves in the Middle East to the Arctic Circle to the depths of the Amazon rainforest. They can be attached to oceanic creatures such as turtles, whales and corals and record day and night.

The tsunami of data being gathered is impossible for humans to analyse. So researchers are training artificial intelligence (AI) to recognise patterns in communication we didn’t realise existed, which can be linked to behaviours and tested in the field using recordings. With these techniques, for example, scientists realised that elephants use different warning calls for “honeybee” versus “human”.

Using sensitive microphones and vibrometers, researchers have discovered plants that emit ultrasonic sounds imperceptible to human hearing, such as young corn plants producing various “click-click” sounds, depending on the extent of dehydration.

Plants don’t have ears but can sense sound and change their behaviour accordingly. By playing recordings of the sounds of caterpillars chewing on leaves, Heidi Appel of the University of Toledo discovered that plants release mustard oil, a defensive chemical unappealing to insects. When she played the sound of an insect that does not eat that plant, the plant did not respond. In a different experiment, buzzing bee recordings stimulate evening primrose flowers to temporarily increase the amount of sugar in their nectar.

In the oceans, microscopic coral larvae can recognise the sound of their own coral reef and swim towards them, and can also distinguish the sounds of unhealthy versus healthy reefs. Bats have complex vocal regimes depending on what they want to talk about- sex, territory, food or other resources. We could not have understood any of this without the power of AI.

In her mesmerising book, Bakker, who died suddenly last August, makes accessible a whole new world of research and evidence, from Indigenous communities to scientists. Scientists are now building databases of animal communication using translation software to decrypt what they are saying. Bakker predicted that we are on the brink of interspecies communication and that within a decade, as scientists create a “zoological version of Google Translate”, humans will have interactive conversations with elephants, honeybees, whales and bats.

[ Noise pollution affects animals’ communication with each other – research ]

Digital bioacoustics could help us regenerate nature; this happened in endangered coral reefs off the coast of Indonesia, where scientists played recordings of healthy coral reefs on underwater sound systems to attract fish and coral larvae as part of ecosystem restoration projects.

Could we communicate with other species? Should we? Would they want to talk to us? What are they saying to each other? And if we could speak to them, what would we say? My teenage self would ask the peahens if the peacock ever did get it out. But today, if I had only one word, it would be this: sorry.

[ How the haunting song of the humpback whale saved it from extinction ]

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