Mlaika is a 10-year-old adolescent female African elephant living in Kenya in a group of semi-captive elephants. During the day she makes sounds you might expect.
But she moonlights as a truck.
"When she is with the other elephants, she makes normal elephant sounds," says Stephanie Watwood of Woods Hole Oceanographic Institute. "But at night, when she is by herself, she can hear the trucks from a nearby highway and imitates their sounds."
Mlaika is one of two African elephants scientists have found making strange sounds. The other one chirps.
Watwood, who co-authored a recent study on the pachyderms bizarre copycat behavior, believes the elephants have learned to make sounds outside their normal repertoire in an attempt to better relate with their neighbors.
But why would an elephant imitate the sound of a truck? Watwood has a couple of suggestions.
"Perhaps it sounded like a distant elephant. She probably made the sounds to try and communicate with it," Watwood told LiveScience.
But it's hard to know what an elephant is thinking, and the creature's reasoning could be even simpler. "She may have been bored and it was something to do," Watwood suggests.
Groups within herds or larger populations often identify other group members using a unique call. Animals such as dolphins, whales, humans, bats and some birds all do this, but no one knew elephants did it too.
"Making a group sound could make it easier to identify other members of the group," Watwood said. "We sometimes see this with other animals – it may be that elephants do this too."
This could certainly be the case for Calimero, a 23-year-old male African elephant who spent 18 years living with two female Asian elephants in a Swiss zoo. To get along with the ladies, Calimero learned to make a chirp-like call that is commonly used by Asian elephants.
African elephants don't make this sound, but now Calimero very rarely makes any sound other than the chirp call. This research was published earlier this year in the journal Nature.
These findings, in combination with recent studies at Sussex University that show elephants can remember calls from other elephants, suggest the beasts may use vocal learning to develop calls to maintain individual-specific social relationships.