Chimpanzees of the Budongo Forest : Ecology, Behaviour, and Conservation

There are four phases of the pant-hoot: the introduction, build-up, climax and letdown
(Fig. 6.8), and these differ in ‘length’ and ‘shape’ in different chimpanzee populations.
Mitaniet al. (1992) added a new dimension to our knowledge of chimpanzee vocal-
izations when they described chimpanzee ‘dialects’ — minor but distinct variations in
the structure of the same call-types in different parts of their range.
Males at Mahale were found to have a faster rate of delivery, shorter duration of
build-up elements and a higher pitched climax than Gombe chimpanzees. Males at
Kibale (Kanyawara community) in Uganda had longer elements in the introduction and
a shorter build-up than at Mahale. Kibale males also delivered acoustically less variable
pant-hoots than those at Mahale. Playbacks of the calls made it possible to determine
where they were from with a greater than chance frequency.
An additional finding was that of Mitani and Brandt (1994) in which they suggested
from an analysis of pant-hoot choruses that chimpanzees could modify their calls to
sound more similar to those they were calling with. They also found that the more
time males spent with each other, the more similar their calls were. This fits with the
‘action-based’ model of vocal learning in birds (Marler 1990). In human terms it can
explain how individuals come to adjust their speech to that of others in the group,
thus, for example, taking on a local accent. This, together with the existence of
dialects in chimpanzees, indicates that over and above the basic call structure of chim-
panzees there are learned components in the calls. Clark Arcadi (1996) suggested that
modification of pant-hoots in a community leads to them coming to resemble those of
the alpha male.
Clark and Wrangham (1994) extended our understanding when they distinguished
between two wholly different aspects of meaning in pant-hoots. On the one hand they
are associated with good quality food, and it was (and is) thought that they attract fellow
members of the community to rich food sources where competition is not so great as to

Pant-hoots 135

Fig. 6.8: A representative pant-hoot sequence from Budongo showing the four distinct phases
(from Notman 2003).

B>SPG 0.00000< 0>

8007

0

0.000 Time (s) 6.247

Freq. (Hz)

Introduction Build-up Climax Let down