The 22-year-old Asian
elephant can reproduce five Korean words by tucking his trunk inside his mouth to modulate sound, the scientists said in a joint paper published online in Current Biology. They said he may have started imitating human speech because he was lonely.
Koshik can reproduce "annyeong" (hello), "anja" (sit down), "aniya" (no), "nuwo" (lie down) and "joa" (good), the paper said.
One of the researchers said there is no conclusive evidence that Koshik understands the sounds he makes, although the elephant does respond to words like "anja" and "nuwo."
Everland Zoo officials said Koshik also can imitate "ajik" (not yet), but the researchers haven't confirmed the accomplishment.
Koshik is particularly good with vowels, with a rate of similarity of 67%, the researchers said. For consonants he scores only 21%.
Researchers said the clearest scientific evidence that Koshik is deliberately imitating human speech is that the sound frequency of his words matches that of his trainers.
Vocal imitation of other species has been found in mockingbirds, parrots and mynahs. But the paper said Koshik's case represents "a wholly novel method of vocal production" because he uses his trunk to reproduce human speech.
In 1983, zoo officials in Kazakhstan reportedly claimed that a teenage elephant named Batyr could reproduce Russian
to utter 20 phrases.
Researchers believe Koshik learned to reproduce words out of a desire to bond with his trainers after he was separated from two other elephants at age 5.
Koshik emerged as a star among animal enthusiasts and children in South Korea
after Everland Zoo claimed in 2006 that he could imitate words, two years after his trainers noticed the phenomenon.
Oh Suk-hun, a South Korean veterinarian who co-authored the research paper with Stoeger-Horwath and Mietchen, said the elephant apparently started imitating human speech to win the trust of his trainers.
Researchers said Koshik was trained to obey several commands and "exposed to human speech intensively" by trainers, veterinarians and zoo visitors.
Shin Nam-sik, a veterinary professor at Seoul
National University who has seen Koshik, agreed with researchers' finding that the elephant was able to mimic human speech.
"In Koshik's case, the level of intimacy between him and his trainer was the key factor that made the elephant want to sound like a human," Shin said.
Kim Jong-gab, Koshik's chief trainer, said the elephant was timid for a male when he first came to Everland Zoo, so trainers often slept in the same area with him. Kim thinks that contact helped Koshik feel closer to humans.
Kim said he has another phrase he wants to teach Koshik: "Saranghae," or "I love you."