Infrasound radar listens for elephant rumbles to warn villagers (Sri Lanka)


New Scientist

Date Published
IN JANUARY an elephant entered Moragoda village in northern Sri Lanka and killed a father in his vegetable garden. In July, a dairy farmer from the east was killed taking his cow out to graze. Now an ambitious project aims to warn communities when elephants approach by tracking these giants around the country via their rumbling calls.

Chamath Keppitiyagama of the University of Colombo is working on a radar system that listens out for the inaudible rumbles of elephants’ infrasound, something that was discovered in the 1980s. Infrasound is useful for locating and tracking elephants over long distances – the low frequency means the sounds travel a long way through the air.

By understanding how elephants move around, communities should be better prepared for encounters, which are becoming more frequent as Sri Lanka’s population of both humans and elephants grow. The human population has doubled since the 1960s to more than 20 million. At the same time, the country’s long-term decline in elephant numbers has reversed. Falling from 12,000 at the turn of the 20th century to 2000 by 1990, elephants have now rebounded to almost 6000. That brings the two groups into conflict. Roughly 70 people die every year, with 250 elephants shot, poisoned or electrocuted in turn.

The researchers are building software to help their sensors pick infrasound out of the background noise. This means recording a lot of elephant grunts. In July, the team travelled to western Sri Lanka to record celebrity elephant Nadungamuwa Raja, one of just a few elephants with a Wikipedia page.

Wouldn’t it make more sense to track elephants with GPS? Keppitiyagama says it has been tried. But making a tracking collar that can stand up to the elephant lifestyle is tough. “Elephants go and dip in lakes, rub their heads on trees and get into muddy ponds, all sorts of things, so this device has to be really rugged, and that means expensive,” he says.

Eva Gross of French NGO Awely, which works on solving conflict between animals and humans, says the infrasound radar is promising, especially in heavily populated countries like Sri Lanka. “I could imagine very well that it could help in areas where you have a dense human population, and people need to be warned whether they can pass through an area by foot or not,” she says. It could also help people guard their crops from elephants, if they knew that they were nearby.

“Infrasound could help people guard their crops if they knew that elephants were nearby”

In tests, the existing setup can identify recorded infrasound from 300 metres away. And real elephants are about eight times louder than the infrasound player. “We expect to detect elephants over a few kilometres at least,” says Keppitiyagama.

Villagers would have enough time to grab tools to fend off the elephants. Gross advocates chilli. “Elephants don’t like the smell of chilli smoke,” she says. “Burning chilli on elephant dung to produce a lot of smoke is a good approach.” Keppitiyagama’s team are working on a chilli gas dispenser that consists of a ping-pong ball filled with chilli oil that can be fired at the elephant.