What do you think of this fact?
When an elephant calls, you often only hear part of it. Another part travels through the earth, and other elephants apparently can feel it.
Calls that run through the ground
Elephants communicate with deep rumbles. According to Physics World, the fundamental frequency of these calls is below 30 hertz, which is infrasound that humans can’t hear. We only pick up some of the overtones.
Stanford researcher Caitlin O’Connell-Rodwell and colleagues looked at what happens in the ground. For a 2004 study, according to Physics World, they laid out a line of 57 geophones, sensors that pick up ground motion, stretching about 175 meters from the enclosure of three African elephants. Their result: the calls create seismic waves that spread through the ground. According to computer models, they can travel more than 2 kilometers.
Listening with your feet
The exciting part is how elephants might pick up these signals. According to ScienceDaily, there are two ideas. Either the vibrations travel through the bones from the foot to the ear, or touch receptors in the feet sense them, similar to those in the trunk. The researchers think it could be a combination. It hasn’t been fully proven yet.
There are clues from the field, though. According to a Stanford University report, O’Connell-Rodwell played female elephants’ mating calls in Etosha National Park in Namibia through a speaker coupled to the ground, so it sent out vibrations as well as sound. The bulls stopped, pressed their trunks to the ground and turned sideways to the direction of the signal.
Bonus fact: According to ScienceDaily, there are anecdotal reports of elephants in Angola moving toward rain falling about 100 miles away. How they notice it is unclear.
A network under your feet
So the image of the heavy, clumsy elephant doesn’t quite fit. Each of those huge feet may hide a sensitive sensor. According to ScienceDaily, O’Connell-Rodwell has worked on the topic since the early 1990s, and her fieldwork began in 1992.
What sounds like silence to us could be a whole conversation for an elephant herd.