Science is making it possible to ‘hear’ nature. It does more talking than we knew

https://www.theguardian.com/commentisfree/2022/nov/30/science-hear-nature-digital-bioacoustics

By placing these digital microphones all over Earth, from the depths of the ocean to the Arctic and the Amazon, scientists are discovering the hidden sounds of nature, many of which occur at ultrasonic or infrasonic frequencies, above or below human hearing range. Non-humans are in continuous conversation, much of which the naked human ear cannot hear. But digital bioacoustics helps us hear these sounds, by functioning as a planetary-scale hearing aid and enabling humans to record nature’s sounds beyond the limits of our sensory capacities. With the help of artificial intelligence (AI), researchers are now decoding complex communication in other species.

As scientists eavesdrop on nature, they are learning some astonishing things. Many species that we once thought to be mute actually make noise – lots of it, in some cases. For example, research by Camila Ferrara at Brazil’s Wildlife Conservation Society has demonstrated that Amazonian sea turtles make more than 200 distinct sounds. Ferrara’s research showed that turtle hatchlings even make sounds while still in their eggs, before they hatch, to coordinate the moment of their birth. Ferrara’s acoustic research also revealed that mother turtles wait nearby in the river, calling to their babies to guide them to safety, away from predators: the first scientific evidence of parental care in turtles, which were previously thought to simply abandon their eggs.

Scientists are also learning that vocally active species – like bats – make sounds which contain much more complex information than previously thought. Bat echolocation, for example, was discovered nearly a century ago. But only recently have researchers begun deciphering the sounds that bats make for other purposes. By recording many hours of bat vocalizations and decoding them using AI algorithms, scientists have revealed that bats remember favors and hold grudges; socially distance and go quiet when ill; and use vocal labels that reveal individual and kin identity. Male bats learn territorial songs in specific dialects from their fathers and, much like birds, sing these songs to defend territory and attract mates, which scientists characterize as culture.

Acoustic tuning is also widespread in nature. Coral and fish larvae find their way back home by imprinting on the unique sounds made by the reef where they were born. Moths have developed echolocation-jamming capabilities to hide themselves from bat sonar. Flowers and vines have evolved leaves to reflect echolocation back to bats, as if they were luring their pollinators with a bright acoustic flashlight. In response to the buzz of bees, flowers flood themselves with nectar. Plants respond to some sound frequencies by growing faster; and some species – including tomatoes, tobacco and corn seedlings – even make noise, although well above our hearing range.