Stephanie Watwood had no reason to expect that two elephants would cross her path. Nor did she anticipate their surprising vocal impersonations.
Not that Watwood was unfamiliar with leviathan-sized mammals. As a biologist at Woods Hole Oceanographic Institution, she studies whale and dolphin communication. Marine mammals are known to forage for prey, broadcast their identity, and establish social bonds using sounds that are transmitted efficiently through water. They can even learn to make new sounds by imitating what they hear—a process known as “vocal learning.”
“We know that humpback whales, for example, sing during the breeding season,” Watwood said. “They learn songs from each other, and the songs change. All the whales within one area will imitate one another and help spread the change in songs from year to year.”
“It’s an ability that’s not very common among animals,” she said. “Songbirds and parrots have this ability, and bats, cetaceans, and pinnipeds (such as seals and walruses), and that’s pretty much it.”
At least until the elephants showed up in her lab. It happened this way.
Joyce H. Poole, a researcher at the Amboseli Trust for Elephants in Kenya, was studying vocal behavior in African elephants, Watwood said. “She had friends who were running an orphanage for elephants, and they had heard this female elephant, Mlaika, making strange sounds, so Joyce went to check it out.
“When Joyce was sitting near the elephant compound, she could hear trucks in the far distance,” Watwood said. “And then, when she was sitting there listening to Mlaika, instantly she said, ‘Wow, she sounds like those trucks I’m hearing!’ ”
Meanwhile, another elephant communication researcher, Angela S. Stoeger-Horwath of the University of Vienna, had discovered a male African elephant named Calimero living in a zoo with female Asian elephants—a different genus and species. He didn’t make any normal male African elephant sounds, but mimicked the chirping calls of his female roommates.
Stoeger-Horwath shared her findings with Poole, and they agreed: These elephants seemed to have learned to imitate unusual sounds. Then they remembered hearing a lecture by Peter Tyack, a WHOI biologist and an expert on vocal learning in marine mammals. That’s how two elephant researchers in Europe and Africa ended up in contact with Watwood in Woods Hole.
“They were looking for someone who would believe that their elephants made funny sounds,” Watwood said.
The two elephant researchers sent Tyack numerical data on the elephants’ calls. Watwood, an expert in analyzing similar data from marine mammal sounds, compared the frequencies and duration of Mlaika’s and Calimero’s calls with the sounds of the trucks and the Asian elephant females. The work of Poole, Tyack, Stoeger-Horwath, and Watwood demonstrated for the first time that elephants, too, have the ability to learn and imitate vocal sounds.
Like whales and dolphins, elephants have strong social structures and they use low-frequency sound to communicate over wide expanses. “People have speculated that elephants communicate over many kilometers,” Watwood said, “and one study showed they can recognize who produced the calls, over considerable distance from at least a kilometer away.”
“Elephants do make those loud trumpet calls, which is what they show on the movies all the time,” Watwood said, “but most of the sounds made by adults are really low-frequency rumbles, below the human range of hearing.”
The sounds that Mlaika and Calimero made did not exactly match the trucks and the Asian elephants, Watwood said, but it was clear that they were trying hard to mimic those sounds to the best of their abilities.
“Truck sounds are very low frequencies, well within the range of sounds that elephants produce,” Watwood said. “The truck sound that Mlaika imitated was a lo-o-o-o-o-ong sound—much longer calls than she normally would make.”
“Calimero is much bigger than an Asian elephant female and so had a lower voice; he called at a lower frequency than females would,” Watwood said. “But he put more of his vocal energy in frequencies that were much higher than a typical elephant of his size would make. He was doing his best to sound like a smaller elephant.”
This research was funded by Woods Hole Oceanographic Institution.
Calimero, a male African elephant in a zoo, learned to imitate the sounds made by female Asian elephants he was housed with. His ability to learn through imitating sounds, called ?vocal learning,? is rare among animals and was previously only known in birds, bats, and marine mammals. (Photo by Angela S. Stoeger-Horwath, University of Vienna)
WHOI biologist Stephanie Watwood studies the sounds whales make to communicate and forage under water. She was asked to apply her expertise to decipher the calls of elephants, which use similar types of sound to communicate. On the screen is the wave form (amplitudes of the call vs. time) of a "chirp" sound made by an Asian elephant. (Photo by Tom Kleindinst, WHOI)