Elephants turn footsteps into messages through ground and skull vibrations‎

Elephants can communicate with other elephants across distances of up to five kilometers (3 miles) by producing sounds that travel through the air. However, they have a second way of sending signals: seismic waves traveling through the ground. These vibrations are transmitted from elephants' feet through their legs and ultimately through the bones of their skull directly into the inner ear. They can be perceived across distances of 10 kilometers (6 miles) or more. This is called bone-conduction hearing.