Early Access: Episode on Elephant Feet!

African elephants may have magnificent ears, but on the savannah, they communicate over vast distances by picking up underground signals with their sensitive, fatty feet.

 Caitlin O’Connell-Rodwell has been a regular at the same watering  hole for more than 25 years. Most of the other patrons are elephants.

This summer marks the Stanford researcher’s 26th visit to Mushara, a  natural freshwater spring in Namibia’s Etosha National Park that gets  heavy elephant traffic. Thousands of elephants in the southwest African  nation roam an area the size of New Jersey, with different groups taking  turns at the park’s numerous watering holes.

O’Connell-Rodwell’s research focuses on seismic communication among  elephants, a field she pioneered back in 1997. Over the years, her work  has shown that African elephants exchange information by emitting  low-frequency sounds that travel dozens of miles under the ground on the  savanna.

The sound waves come from the animals’ huge vocal cords, and distant  elephants “hear” the signals with their highly sensitive feet.

“When an elephant vocalizes, it’s like a mini-explosion at the source,” said O’Connell-Rodwell.

The sound waves spread out through the ground and air. By  triangulating the two types of signals using both ears and feet,  elephants can tune in to the direction, distance and content of a  message.

“It would be similar to counting the difference between thunder and lightning,” she said.

According to O’Connell-Rodwell, seismic communication is the key to  understanding the complex dynamics of elephant communities. There are  seismic messages that are sent passively, such as when elephants  eavesdrop on each other's footsteps. More active announcements include  alarm cries, mating calls and navigation instructions to the herd.

 Seismic communication works with elephants because of the incredible  sensitivity of their feet. Like all mammals, including humans, elephants  have receptors called Pacinian corpuscles, or PCs, in their skin. PCs  are hardwired to a part of the brain where touch signals are processed,  called the somatosensory cortex. 

 In elephants, PCs are clustered around the edge of the foot. When  picking up a far-off signal, elephants sometimes press their feet into  the ground, enlarging its surface by as much as 20 percent!

Let us know in the comments if you have any questions about this episode, or ideas for upcoming episodes.