Watch a video of playback to few male chimpanzees.
Watch a video of playback to many male chimpanzees.
In the first experiment, the party
consisted of two males: Light Brown and Makoku. After hearing
the foreign male pant-hoot (which is very faint on the video
tape), both males remained silent. After two minutes, Light
Brown climbed down from his tree and moved a short distance
towards the speaker. After reaching a trail intersection, Light
Brown sat and waited from Makoku to join him. Light Brown
repeatedly glanced back towards Makoku and then towards the
speaker. Only after Makoku joined Light Brown did he begin
moving towards the speaker.
In the second experiment, a party with six males and two
mothers with their kids fed in a big fig tree. As soon as the
foreign male pant-hoot was played, the males responded with a
chorus of loud calls, climbed rapidly down the tree, and walked
quickly straight towards the speaker. The two mothers stayed
behind in the tree.
