Amazing stuff.
I went to Paignton zoo last year and the Macaque enclosure had instructions of how to communicate with them by using about 10-12 gestures. It worked pretty well, I can't remember the gestures, but I do remember that they were using them quite well. When we used the gesture, they gave appropriate gestures back to us.
I don't know if it was trained behavior or natural behavior, but it was pretty cool.







