In the wilds of Africa, when it’s time for a family of elephants gathered at a watering hole to leave, the matriarch of the group gives the “let’s-go rumble” — as it’s referred to in scientific literature — kicking off a coordinated and well-timed conversation, of sorts, between the leaders of the clan.First, the head honcho moves away from the group, turns her back and gives a long, slightly modulated and — to human ears — soft rumble while steadily flapping her ears. This spurs a series of back and forth vocalizations, or rumbles, within the group before the entire family finally departs.This curious behavior, measured and documented in a study published in the October issue of Bioacoustics, shows how this cognitively advanced species uses well-coordinated “conversations” to initiate cooperation within the group, said lead author Caitlin O’Connell-Rodwell, PhD, a field biologist and instructor in otolaryngology at the Stanford University School of Medicine. The use of “rumbles” to initiate departure helps explain the group’s ability to work together to achieve 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.”The study also indicates how this behavior uses rumbles in a structured way to transmit signals longer distances both through the air and through ground vibrations that could alert other elephant family groups not to approach the watering hole until they’re gone, thus avoiding the mass chaos of too many large, noisy bodies at the same watering hole at the same 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.O’Connell-Rodwell has studied the elephants of the Mushara area of Etosha National Park in Namibia for 20 years, spending most of her summers hunkered down in a bunker or perched atop a tower cataloging more than 170 identified bulls and more than 15 family groups to understand the importance of long distance communication through both the air and ground. She is the author of the nonfiction science memoir, The Elephant’s Secret Sense, which highlights her earlier work on elephants’ ability to communicate by producing and listening to underground vibrations. She has also written one for children called The Elephant Scientist, which won both the Sibert and Horn Book nonfiction honors.