reduce their own ability to find as much food as they want.^59 On the other hand they
found that the frequency of arrivals of other chimpanzees supposedly ‘called’ to feeding
trees by pant-hoots was no greater than the frequency of arrivals when no pant-hoots had
been given. They noted that pant-hoots were often given by males when they were near,
but out of sight of, their alliance partners, and concluded that these calls were equally or
more likely to be given by adult males when locating or ascertaining the presence of
alliance partners.
At Sonso chimpanzee vocalizations have been studied by Wong (1995) and Notman
(1996, 2003, in press). Both Wong’s study and Notman’s first study were comparative.
Wong compared Budongo pant-hoots with those described for Gombe, while Notman
compared Budongo pant-hoots with those of Kibale.
Wong, in her 1995 study, examined the pant-hoot calls of two populations of chim-
panzees to see whether there were differences (possibly ‘dialects’). The calls from
Gombe she used for the comparison study were made by Charlotte Uhlenbroek in
1993.^60 32 calls from seven Sonso individuals^61 were compared with 34 calls from five
Gombe individuals. The alpha male contributed largely to these samples in each case.
Wong focused on the build-up and climax phases of the pant-hoot in her analysis,
following the methods used by Mitani et al. (1992) and Mitani and Brandt (1994).
The differences between the build-up and climax phases of the pant-hoots of
Budongo and Gombe chimpanzees are summarized in Table 6.5. The results of Wong’s
analysis indicated that the rate of delivery of the build-up elements is the only para-
meter that differs significantly between Gombe and Budongo chimpanzees. Budongo
chimpanzees have a slower rate of delivery than Gombe chimpanzees. The differences
in duration of build-up elements and frequency of the climax elements found by Mitani
et al. (1992) when they compared Gombe with Mahale were not found in Wong’s
comparison of Gombe and Budongo.
In addition Wong looked at the question of whether, as mentioned above, individuals
may be influenced in their call types by those around them, giving rise to accents and
dialects. ‘This’ she wrote ‘seems a plausible explanation for the difference in call structure
between Budongo and Gombe chimpanzees.’ She also noted that there was no significant
variation within populations, suggesting that there may have been ‘convergence’ among
individuals of the same population.
As to the function of regional accents, Wong followed Goodall’s (1986) suggestion
that distinct community accents might have arisen for reliable and easy recognition of
136 Social behaviour and relationships
(^59) This ‘meaning’ was rejected when I first suggested it in 1965. I was told in the friendliest possible way
that the existence of competition between individuals would eliminate any possibility that pant-hoots could be
telling others of the location of good food: individuals would be expected to keep quiet about such things and
enjoy them in peace! It was only later, in the 1970s, when the degree of co-operation between males (who do
most of the pant-hooting) was discovered, together with the advent of sociobiology, that zoologists were able
to take on board that pant-hoots might indeed be co-operative calls. Up to that point these ideas were regarded
as unscientific.
(^60) Wong acknowledges Uhlenbroek’s generosity in making her recordings available for the comparison.
(^61) Most calls were from the alpha male Duane, and she established that there was no statistically significant
difference between repeated pant-hoots by this male, i.e. his pant-hoots (and probably those of others) had
a distinct pattern, repeated each time he called.