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Transcript of Playbacks Videos
Michael Wilson
The contrast between these two experiments illustrates the main result: chimpanzees can "count"; they make more noise and approach faster the more they outnumber the intruder.
I've transcribed the voices on tape, giving the two-letter code of the speaker.
I've also added various notes about what is going on on the tape in square brackets [].
People:
MW: Mike Wilson
JR: John Barwogeza
MD: Donor Muhangyi
FM: Francis Mugurusi
Playback Few
14 May 1998
[At start of video, mainly just trees are visible, but there really are chimps there, and I've started the tape just a few seconds before the playback. Two adult males, Light Brown and Makoku, fed quietly on ripe fruit in a grove of Uvariopsis trees. No other chimpanzees were nearby. The speaker was located up the hill about 200 m away.]
MW: "Can see Light Brown moving towards the center of the picture there."
MW: "And Makoku is climbing down as well, over there."
MW: "That's the call."
[The playback pant-hoot can be heard very faintly in the distance. I sounded clear in real life but didn't record well on the video tape. Researcher Martin Muller can be seen at the bottom of the screen just after the playback pant-hoot.]
MW: "7:27. No vocal response from the chimps here."
MW: "7:30 and Light Brown is traveling away."
[Light Brown walks ahead of me on the ground.]
MW: "Here he is. He's moving away from the speaker a bit."
[At this point I had not yet got my bearings as Light Brown was traveling off trail in a very bushy area. Later measurement of points marked along his path showed that he moved directly towards the speaker, taking an off-trail short cut to a series of trails that went strait to the speaker.]
MW: "He stopped to rest."
[Light Brown sits down and looks back towards me. He's waiting for Makoku to come down.]
MW: "He's looking towards me. And the calls came from behind me."
[I'm still disoriented at this point. The playback call actually came from behind Light Brown; he's sitting with his back towards the playback location, which is over 100 m away].
MW: "He's just sitting down and looking now. Time is 7:31. He's looking around. His hair's not erect. He's looking in the direction of the speaker now."
[By this point I had figured out where I was and realized that the speaker was behind Light Brown.]
MW: "He's looking towards the speaker again, glancing around. He's still looking towards the speaker."
JR (on radio): "Mike, do you read me?"
MW: "Yes, I read you John."
JR: "Where are the chimps now?"
MW: "They climbed down from the tree and they moved a bit, but they aren't coming towards you yet."
JR: "Donor has already gone."
[Immediately after the playback, John and Donor packed up the equipment and Donor carried it away so the chimpanzees would not see it. John remained hidden at the speaker site.]
MW: "Okay, very good."
MW: "Light Brown is still sitting by himself. Makoku is still feeding. I can hear something moving. Light Brown's looking towards him now. We haven't heard any other chimps in the area respond to the pant-hoot."
[It's a few minutes later and Makoku has finally joined Light Brown in the approach to the speaker.]
MW: "Here come's Makoku, and he's moving up the trail going towards LB. And this trail should be taking us closer to the speaker location. Time now is 7:37 and 39 seconds."
[Makoku walks slowly up the trail following Light Brown, who is up ahead, out of sight. Note that it took a full 10 minutes for both chimpanzees to join in the approach to the speaker.]
MW: "So the chimps weren't moving at all before the experiment. 7:38 Makoku just sat down. He's looking towards the speaker it seems."
[End of video. Light Brown and Makoku eventually reached within 50 m of the speaker]
Playback Many
31 July 1998
[At the start of this experiment, the chimpanzees were feeding in a large fig tree. The party included six adult males (Johnny, Big Brown, Imoso, Stout, Tofu, and Yogi), two mothers (Outamba and Tongo) and their kids (Kilimi, Tenkere, and Lanjo). We can see Imoso, the alpha male, resting on a branch in a fig tree, silhouetted against the morning sky. The speaker was located across a steep valley about 460 m away.]
MW: "7:32:51. 7:33."
[The playback pant-hoot can be heard clearly in the distance. Imoso and the others immediately call and climb down the tree. The camera pulls back, showing half a dozen males clambering down from the fig. The camera turns towards the trail, where Francis Mugurusi is recording chimpanzee calls and dictating notes on a microphone. Francis can be heard talking quietly while the males one by one file out on to the trail and begin moving towards the speaker.]
FM: "At 0733.10 we heard the playback. And immediately chimps started running towards the speaker, Yogi being the first to climb down the tree. And immediately moved toward the direction of the speaker. . . . And the chimps responded with waas and charge displays. They are now moving in a straight line, Yogi leading, being followed by Big Brown, then Imoso, Johnny, Stout."
FM: "Yogi's leading, being followed by Stout, then Imso, Big Brown, Johnny at the last."
[End of video. The males eventually reached within 30 m of the speaker.]
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