BETHESDA, Md. (Sept. 18, 2009) —Caitlin O'Connell-Rodwell's insight that elephants 'talk' and 'listen' to vocalizations that they send through the ground grew from long hours of observation and experimentation, as well as her own in-depth knowledge of insects that communicate seismically.
In Episode 25 of the APS podcast, Life Lines, the Stanford University professor updates her research from the APS journal Physiology, explaining how elephant vocalizations travel through the ground for great distances, and how other elephants can understand them, just as they understand acoustic sound, which travels through the air. The study in Physiology can be found by clicking here or by following the full link at the end of the release.
Dr. O'Connell-Rodwell is the author of The Elephant's Secret Sense. You can see videos of some of the elephant communication experiments she describes in the podcast on her Utopia Scientific site. The links to the videos are on this page: http://utopiascientific.org/Research/mushara.html .
Discovers seismic communication
Early in her research, Dr. O'Connell-Rodwell noticed behavior that indicates elephants are listening to acoustic (airborne) sounds by putting their ears out and orienting toward the sound's source.
At other times, she also noticed a more puzzling behavior: Several elephants would freeze simultaneously, sometimes in mid-stride, and would press their front feet into the ground. They might also roll a foot forward so that only their toes touched the ground. At other times, they would lift a front leg. The behavior reminded her of the behavior she saw in insects that communicate seismically.
She began a series of experiments that eventually found that:
Further research revealed that there are two ways elephants 'hear' sound waves traveling through the ground:
Somatosensory pathway. Elephants feel the sound wave through their feet and trunks using the somatosensory pathway. Their feet and trunks have a large number of pacinian corpuscles -- cells that detect vibrations. The cells help transmit these vibrations to the brain.
Bone conduction pathway. Elephants detect ground-borne sound waves through their toenails. The vibration travels up the bone and into the middle ear where it vibrates the middle ear bones, just as an acoustic sound would.
Elephants also have anatomical adaptations to help them 'hear' these ground-borne vocalizations:
You can find the podcast interview at http://lifelines.libsyn.com/index.php?post_id=524100 and an article on the research in the journal Physiology: http://physiologyonline.physiology.org/cgi/search?sortspec=relevance&author1=O%27Connell-Rodwell&fulltext=&pubdate_year=&volume=&firstpage= .
For more information, please contact Christine Guilfoy at cguilfoy@the-aps.org or at 301.634.7253.
Physiology is the study of how molecules, cells, tissues and organs function to create health or disease. The American Physiological Society (APS) has been an integral part of this scientific discovery process since it was established in 1887.