Tilda, a female orangutan at the Cologne Zoo in Germany, appears to have figured out that if she communicates like a person, she can better grab the attention of zookeepers.

She is the first wild-born Bornean orangutan known to produce novel human-like vocalizations, according to a paper published in PLOS ONE. She is also the only wild born orangutan that can whistle tunes, just as humans do.

Tilda's background is somewhat of a mystery, but it's suspected that as a youngster, she was a circus animal.

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"It is our belief that Tilda learned to produce these calls from humans while she was in the entertainment business, putatively by copying a human trainer," lead author Adriano Lameira of the University of Amsterdam's Institute for Biodiversity and Ecosystem Dynamics, told Discovery News. Tilda is now producing the calls all on her own without prompting, and with a specific goal in mind.

Lameira and his team came to these conclusions after making video and audio recordings of Tilda and then analyzing her communications. Two of her calls are unknown among other orangutans and show human-like characteristics, the researchers conclude.

For one call, Tilda clicks her tongue to produce different tones, just as a human can. The process she goes through to make the sounds is comparable to a human producing voiceless consonants, such as saying the letters "p," "k" and "t."

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For the other call, Tilda grumbles in a way that's comparable to humans producing vowel sounds. Both calls require that she rapidly open and close her mouth in rhythms similar to those of human speech.

The meaning of her calls is clear, because she often claps or extends her index finger towards food in the caretakers' hands as she vocalizes.

"They are what we would call attention gathering or come-hither calls, which indeed are mostly used when the human caretakers are handling food," Lameira said. "I would translate them into, 'Come here and give that food to me!"

Tilda the orangutan.archive Cologne Zoo

Aside from revealing Tilda's cleverness, the findings suggest that the common ancestor of great apes possessed the capacity to learn and produce both vowel and consonant-based calls. This is supported by studies on other primates.

Chimpanzees, for example, engage in novel call production. Koko, a human-raised gorilla, sometimes babbles on her toy phone.

Lameira said that in the wild, orangutans create their own "call cultures," where different populations produce their own unique vocalizations.

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"The notion that great ape calls are hard-wired and inflexible is likely an artifact of our very poor understanding of the call communication of these species, rather than that their calls are factually hard-wired or inflexible," Lameira added.

Tilda might meet her match in another adult orangutan, Bonnie.

"Bonnie, a female orangutan at the National Zoo in DC, taught herself to whistle for what seems simply to be the pleasure of it, though there's no whistling known to be part of the call system of any wild apes," Mark Sicoli of Georgetown University's Department of Linguistics told Discovery News.

"What Bonnie shows is that anatomically, whistling would have been in the range of potential sound making behavior of Archaic Homo sapiens, including Neanderthal and earlier hominins like Homo erectus and Australopithecines," he added.

Some of the earliest human languages were also produced by making clicking sounds, such as the "click language" of the Bushmen of the Kalahari Desert. Orangutan vocalizations, as Sicoli and Lameira indicate, could therefore help us to understand the emergence and evolution of human speech.