Elephant tremors only good for intimate 'chats'.

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Author: Hogan, Jenny

THE idea that the deep, rumbling sounds used by elephants to "talk" to each other can also travel long distances through the ground has bitten the dust. A team of leading researchers had suggested that other elephants, presumably too far away to hear sounds, could detect these seismic signals through their feet, but now the same team has shown that the vibrations don't travel nearly far enough.

It is clear from the way elephant herds behave that they can communicate over long distances. When grazing on the African savannah, for example, groups travel along parallel paths a few kilometres apart, avoiding conflicts over who gets to eat the grass. Some observations suggest that the elephants can pick up signals other than sound. For example, a whole herd will sometimes suddenly freeze, with the animals lifting one foot into the air. Their ears don't scan, indicating that they are feeling for a signal rather than listening for it, says Caitlin O'Connell-Rodwell of Stanford University in California.

So when her team suggested in 2000 that seismic vibrations generated by elephant sounds could be picked up by other elephants nearly 16 kilometres away â€" much farther than the sound itself could travel â€" the idea got plenty of attention. But other elephant experts were sceptical. "A lot of it was overblown," says Mya Thompson, from the Elephant Listening Project at Cornell University in Ithaca, New York. It was "too big an extrapolation of too little data", she says.

Now O'Connell-Rodwell and her team are confirming their critics' misgivings. The scientists took an African elephant out into the farmland around Salinas in California and used a network of geophones to pick up the vibrations that ran through the ground when the elephant rumbled. They found that the rumbles produced very low-frequency surface waves in the soil, similar to those generated by earthquakes (Geophysical Review Letters, vol 31, p L11602).

But in the soft Salinas soil, the vibrations travelled only a few hundred metres before dying out, says Roland Günther, a geophysicist on the team. If the elephant had been standing on harder rock, the waves might have made it 2.2 kilometres. But even that is "pretty generous", he says.

Thompson finds the new results much more reasonable. She and O'Connell-Rodwell agree that it does not rule out the possibility that elephants can feel seismic signals, but makes it unlikely that they use them to communicate over long distances. Sound can travel 10 kilometres in good conditions, so news will reach elephants' ears rather than their feet.

"The vibrations made by the African elephant only travelled a few hundred metres before dying out"

PHOTO (COLOR): Can anybody hear me?

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By Jenny Hogan