Chapter 9. Elephant Communication

Elephant Communication

Read the article below. Then answer the questions that follow.

Rabbits and skunks use "foot thumping" to warn others against predators. It now appears that elephants use a similar form of communication.

Communicating through seismic waves

When it comes to long-distance communication, having giant ears and a big mouth might not be as useful as you would imagine. Sound tapers off with distance, a problem worsened by wind, thunder, and background noise.

A surprisng, but effective way in which some animals communicate is through the ground. Researchers have long known that kangaroo rats, rabbits, skunks, and other mammals use foot-thumping to transmit mes- sages, warning others against predators. Now, findings indicate that elephants also are capable of communicating through seismic waves. Seismic waves function much like sound, only they still can be detected after traveling miles through the surface of the earth.

Listening with their feet

In the vast expanse of African grasslands, wild elephants sometimes lift one leg to “eavesdrop” on neighboring families. However, they are listening with more than their giant ears; elephants use their big feet to detect sounds. This is possible because the vocalizations produced by elephants travel through the surface of the ground as well as through the air. Low-frequency elephant vocalizations cannot be detected by the human hearing, however they are able to travel through the ground in the same waveform as they do in the air. These ground vocalizations can travel faster or more slowly than sounds in the air (depending on the soil type and condition). However, ground sounds can travel much further than sounds in the air.

Elephants not only use their large ears to detect sounds; they also use their feet to detect seismic communication.

Researchers believe that elephants’ large diaphragms and nasal cavities allow them to generate noises at a low enough frequency and high enough amplitude to travel through the ground.

This seismic communication system works like a “caller ID” of sorts, according to recent research published by Stanford University biologist Caitlin O’Connell-Rodwell. Elephants can distinguish between the vocalizations transmitted by different groups, and they only respond to the warning sounds made by familiar herds.

At a watering hole in Namibia’s Etosha National Park, O’Connell-Rodwell began playing two recordings of elephant vocalizations. One recording featured the sounds of local elephants responding to a nearby lion. The second contained nearly identical sounds but was recorded on the other side of the continent in Kenya. In both cases, the transmitters were buried 20 meters from the watering hole. An amplifier was used to raise the signals so they resembled the real-world rumbles of elephants at this same distance. Groups of elephants were then monitored as they visited the watering hole and responded to the recordings.

Researchers buried amplifiers near a watering hole (like the one pictured here) in Namibia's Etosha National Park and observed elephants' behavior when different recordings of foreign elephants and neighboring herds were played.

When silence or random sounds were played as a control, the elephants did nothing. There also was little reaction to the warning signals from foreign elephants. However, when recordings of neighboring families were transmitted through the ground, the elephants clustered more tightly, flattened their ears to their heads, vocalized a response, and stood on tiptoe. Some even “kept their ear to the ground” by raising one leg.

“When elephants are listening with their ears, they have huge, extended ears,” says O’Connell-Rodwell. “But in this instance, the ears remained flat.”

Statistical analysis similarly confirmed that the elephants were responding to alarm vocalizations.

Elephants are one of the only large mammals known to use “seismic communication” as a mode of information transmission. Along with detecting vocalizations transmitted through the surface of the earth, elephants may also distinguish vehicles, helicopters, and airplanes. They may even have sensitive cells in their feet which detect vibrations.

“It’s a much richer communication system than we thought,” says O’Connell-Rodwell.

© 2015 WH Freeman and Company.

9.1 Comprehension Questions

Answer the following questions to demonstrate your understanding of the article.