Elephants produce seismic ground signals that travel farther than their airborne calls

Evidence

The Asian elephant (Elaphus maximum) has been shown to use signals associated with rumbles and foot stomps. The acoustic signal travels at 309 m/s and the seismic signals at 248–264 m/s. Both signals have a predominant frequency of 20 Hz. The seismic waveforms can be detected at a distance of 16 km. If the elephants are able to detect such waves the communication between the different familiar groups could be maintained also at long distance (O’Connell-Rodwell et al. 2000). — Almo Farina, Soundscape Ecology, 1800