Those notes are a symphony to the ears of primate researchers who believe her musical abilities could lead to a greater understanding of how human speech evolved.
"I think what makes it significant is that you can train apes to whistle, but no one trained her to do it. She decided to do it on her own," says Erin Stromberg, who works in the National Zoo's Great Ape house and helps care for the orangutans.
Stromberg helped publish a recent paper on Bonnie's talents. Researchers believe Bonnie was trying to imitate the sounds of zookeepers who whistle while they work. Stromberg says Bonnie's ability to copy that sound is powerful evidence that apes can re-create the sounds of other species.
"So what's significant about Bonnie learning to whistle is not that she's able to do it, it's that she saw someone else do it and just picked it up," Stromberg says.
For more, and to hear a recording, visit the original story at NPR.