WHEN it comes to communicating over very long distances, an elephant's feet may be more effective than its mouth.

Lynette Hart of the University of California at Davis and her colleagues were studying how easily elephant cries travel in the ground and in the air. When they made elephants cry by placing a boisterous rooster in their pen, the animals also stomped the ground.

Ground microphones set to pick up the low-frequency cries also caught the powerful stomping, which was nearly inaudible in the air. The team say that animals 50 kilometres away—at least five times further than their cries carry above or below the surface—could conceivably detect the noise. The results were announced at last week's Acoustical Society of America meeting in San Diego.

Hart says there is anecdotal evidence that elephants detect noise from such a distance. "People say elephants run in the opposite direction if other elephants, even very far away, are being killed."