Researchers at the Stanford University School of Medicine have discovered that female elephants in estrus can issue a low-frequency seismic call that travels through the soil.In addition to their audible sounds, female elephants also produce low-frequency calls that can travel up to several kilometers through surface soils. Elephants have two systems that are highly developed for detecting such sounds: bone conduction, in which the low-frequency signals are detected by the bones in the feet and travel internally to the middle ear; and somatosensory reception, in which specialized nerve cells in the feet send signals directly to the brain.
Bull elephants can detect these low-frequency signals by using their feet and placing their trunks to the ground. Experiments showed that elephants placed their bodies perpendicular to the direction of the sound, creating the maximum distance between detection points to distinguish the source. Placing the trunk to the ground allows another detection point, allowing the elephant to triangulate the origin of the sound.
Seismic communication has been found to be used in some insect species but this is the first evidence for its application in mammals. Humans also possess both methods of sound detection, although our ability to use vibrations for communication is much less developed.
These results were originally announced in 2007 by the Stanford University School of Medicine.
Source: ScienceDaily
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