Scientists were stunned when they first heard Bonnie whistle.
The 30-year-old female orangutan at the Smithsonian National Zoo
had never been taught to whistle, but she figured out the trick
all by herself back in the 1980s, according to her caretakers.
That makes her the first documented case of a primate
spontaneously mimicking the sounds of another species—in this
case, humans. Though she can’t carry a tune, Bonnie seems to
enjoy whistling and will usually happily comply when asked to do
it. You can even watch her whistle on Youtube. The researchers,
who published a paper on Bonnie in the journal Primates
[subscription required], say she also taught another orangutan,
Indah, how to whistle. Bonnie and Indah dispel the theory that
orangutan vocalizations are only involuntary reactions to
stimuli, and are mainly determined by evolutionary factors.
Instead, whistling orangutans suggest that orangutans can learn
and teach each other new vocalizations. This would explain why
separate populations of orangutans i