New research indicates that elephants have a much keener means of hearing aside from their large, saucer-like ears: their feet. Elephants use their vocal chords to make sounds, which enter the ground as sound waves. Other elephants receive the waves through their feet, which then travel up their leg bones through their shoulder and into their middle ear, eventually reaching the auditory cortex region of their brain.
The researchers, a group of scientists from Stanford University, UC San Diego, and the Oakland Zoo, traveled to Etosha National Park in Namibia to observe herds of elephants. To conduct the experiment, they sent three sets of tones through the ground, each 15 seconds in length. The first set was a warning call from elephants located in Amboseli National Park in Kenya. The second set was a series of meaningless tones. The third set was a warning call from other Etosha elephants.
Of the 456 animals that were observed, none reacted to the Kenyan elephants warning call or to the meaningless tones. When the elephants heard—or rather felt—the third tone and recognized it as an Etoshan warning call, the animals gathered together in a huddle.
This hearing capability may serve as an elephant’s best form of communication and survival tactic. Not only are elephants able to communicate with one another, but one herd is able to warn another of predators from miles away. The study indicates that elephants are able to distinguish frequencies that vary by 0.75 hertz (humans are only capable of distinguishing frequencies varying by 2 hertz).
The new research also shows that elephants use vibration-sensitive nerves located not only on the bottom of their feet, but also in their trunk to carry seismic signals directly to the somatosensory cortex. The somatosensory system is the part of the brain that registers touch and pressure, temperature, pain, and muscle movement. In other words, elephants use the information gathered through their feet as a type of balancing system, helping them know when conditions have changed or they may be under threat.
This study was covered by the Los Angeles Times and will appear in full length this summer in the Journal of the Acoustical Society of America. Posted by Kiki Namikas.
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