October 3, 2012
Elephants Rely On Communication For Organization Of The Family Group
April Flowers for redOrbit.com - Your Universe Online
A family of elephants deep in the semi-arid African savannah gathers around a watering hole, drinking, bathing and resting. The matriarch moves away from the group, turns her back and gives the "let's-go-rumble" — as it is referred to in scientific literature. This starts a coordinated and well-timed conversation between the leaders of the family, signaling that it is time for the entire family to leave.
The elephants' conversation, measured and documented in a study published in the October issue of Bioacoustics, illustrates how this cognitively advanced species uses well-coordinated vocalizations to initiate cooperation within the group. Caitlin O'Connell-Rodwell, PhD, a field biologist and instructor in otolaryngology at the Stanford University School of Medicine explains that this allows the group to accomplish more complicated tasks, such as rescue operations to save a calf from drowning.
"These vocalizations facilitate the bonds between the elephants to be able to work together," said O'Connell-Rodwell, who has been studying African elephants in the wilds for 20 years. "It's the measure of an organized society. It demonstrates how another social animal grouping organizes itself through vocalizations."
This curious behavior uses rumbles in a structured manner to transmit signals over longer distances, both through the air and through vibrations in the ground. This could alert other family groups not to approach the watering hole until they are gone, preventing the chaos of too many large, noisy bodies in one place at one time.
"I've seen 200 to 300 elephants at the same watering hole at one time before. There's a lot of vocalization and pushing and shoving and screaming and roaring. You can see why they'd want to avoid that," she said.
Studying the elephants of the Mushara area of Etosha National Park in Namibia for 20 years, O'Connell-Rodwell has spent most of her summers hunkered down in a bunker or perched atop a tower. She has cataloged more than 170 identified bulls and more than 15 family groups attempting to understand the importance of long distance communication through both the air and ground. O'Connell-Rodwell has written two non-fiction books from this research; The Elephant's Secret Sense, which highlights her work on elephants' ability to communicate by producing and listening to underground vibrations, and The Elephant Scientist, a children's book that has won both the Sibert and Horn nonfiction honors.
In her current study, O'Connell-Rodwell focused on sounds. While observing the elephants in the wild several years ago, she noticed this watering hole "departure" conversation. Between July 1994 and July 1995, researchers set up observation sites at five watering holes in the Etosha National Park using instruments to provide acoustic measurements and charting behaviors.
The scientists counted the number of vocalizations beginning as the family groups arrived at the watering hole up until just after their departure, and found that only three of the 15 to 30 members of the group participate in the departure conversation. This fits with what is known of the elephants' hierarchical power structure.
"They have a matriarch," O'Connell-Rodwell said. "Then there's this sort of secretary-of-state character, and then you have the general who brings up the rear." An elephant family consists of the female offspring of the matriarch and their calves. Somewhere between the ages of 12 and 15, male elephants leave the family units to join bull bands.
O'Connell-Rodman describes the rumble, "It's similar to listening to a truck in the distance. It's really striking, low frequency. You can almost imagine the cycling of the sound wave. It's kind of a throbbing in your chest."
Her research confirms that elephants use vocalization to coordinate action and that usually three callers are involved in this coordinated turn-taking conversation.
"It's not just a chorus," O'Connell-Rodwell said. "As soon as one call ends, another call starts, then the next, then the next. It's connected like a string. Effectively they take a three-second call and turn it into a nine-second call."
The observations revealed that the rate of coordinated calling significantly increases after the initiation of departure, especially when compared to the pre-departure period. In 14 of these "conversation" episodes, 33 percent occurred pre-departure and 66.7 percent occurred during departure.
"These bouts increased in number as the elephants departed the waterholes," the study states, indicating that, they "appear to be true communicative events."
The females use this communication to work together to perform other tasks as well. O'Connell-Rodman describes a scene she has witnessed several times over her 20 years of observation; the leaders of the family working together to save a calf from drowning.
"At our site, we occasionally get newborns falling into the trough. Sometimes the younger mothers get scared and traumatized; they swing their trunk around panicking. They don't know what to do. I've seen the matriarch and another high-ranking female kneel down and wrap a trunk around the baby and pull them out. The little calf is so distraught, the older siblings come and calm him down."
The use of longer, repeated calls is a method of communicating messages at longer distances to other herds, the study suggests. By increasing the length of the signal through both air and ground, the repetition makes the calls more easily detectible at a distance.
"Most likely they're intending to send a message at a distance," O'Connell-Rodwell said. "It's a great recipe for getting your sound to transmit much further."
O'Connell-Rodman's research is showing signs of being useful in human communication as well. She is drawing analogies between humans and elephants in research with hearing aids. Because the hearing-impaired are much better at feeling vibrations, they could benefit from research like this that shows how longer, repeated vibratory signals are made and could be more easily detectible.
O'Connell-Rodman's research was funded by the United States Agency for International Development / World Wildlife Fund-US, Namibia Nature Foundation, UC-Davis, Stanford University and the Seaver Institute.