Most elephant communication occurs at frequencies too low for people to hear.

At Disney's Animal Kingdom in Florida, Anne Savage studies elephant communication in a carefully crafted replica of an African ecosystem. Using microphones to record vocalizations too low for human ears to discern, Savage is categorizing the calls and matching them with potential meaning. In "Elephant Rumbles," she tells Alan, "it seems like it's been a very quiet day, then we'll come back into the lab and find out they've been chatting up a storm."

After long hours logging behavior and matching it to the vocalizations, Savage has made at least two discoveries that illuminate the lives of elephants. First, elephants chatter more to strangers than to friends. Second, females rumble more when they are ready to mate - about 21 days prior to ovulation, which happens just once every four years. This suggests to Savage that the females are announcing their impending fertility to males, who then have three weeks to sort out mating rights amongst themselves.

How far away can elephants communicate? That's what Stanford researcher Caitlin O'Connell is investigating. Her work with wild herds in Etosha National Park in Namibia suggests that in theory, elephants' infrasonic rumbles could set up seismic tremors in the ground that travel up to 30 or 40 miles. But whether or not the elephants can detect these tremors or interpret them as meaningful communication remains unknown.

O'Connell trains a domestic elephant to test her ability to hear through the ground.

At the Oakland Zoo in California, O'Connell has set up an experiment to determine just that. O'Connell has trained an elephant named Donna to raise her foot at the sound of a rumble. Now, using a ground-shaking machine that vibrates in the same range as the elephant rumbles, O'Connell tries to figure out if Donna will respond to the seismic tremors of a rumble the same way.

Alan sits with the researchers about 100 feet away from Donna as the experiment begins. At first, it seems as though Donna does raise a foot when she feels the seismic tremor. But later, Donna also raises a foot in the absence of such a signal. Is she picking up on cues from her trainers? It's not yet clear, but with more patient researchers like Savage and O'Connell on the case, it probably won't be long before we have more answers. As Savage tells Alan, "Trying to figure out what all of it means is very, very exciting."

For more on this topic, see the web feature:
Seeing With Our Ears