other groups in order to avoid agonistic interactions and I strongly concur with her on
this. Having observed the reaction of members of the Sonso community to calls coming
from the Waibira community to the north, it is clear that they not only know they
are from foreign neighbours but show fear of them and when they hear them they move
away fast to the south. This is less the case with their western neighbours, the
Nyakafunjo community, whom they appear to fear less, and with whom we have seen
them involved in border confrontations from time to time.
A year after Wong’s study, Notman (1996) continued this work with his comparison
between the Sonso chimpanzees and those of the Kibale Forest, some 150 miles to the
southwest of Budongo. Being closer to Budongo than Gombe we might expect differ-
ences between these two populations to be slight, and the existence of Bugoma Forest
and numerous forest outliers and patches of forest between Kibale and Budongo means
that, at least until recently, there is likely to have been some degree of contact between
chimpanzees of the two forests. Following the ‘action-based’ model used by Wong,
Notman added some subadult males to his sample to see if their vocalizations were less
standardized than those of adults, as might be expected if they were in the process of
conforming to the local dialect.
Notman analysed 17 usable calls from Budongo and also used 10 calls from Wong’s
study. For the calls from Kibale he used 39 calls from Clark Arcadi’s sample. Both sam-
ples were heavily based on the alpha male of the two communities as were the samples
in Wong’s study.
Pant-hoots 137Table 6.5: Mean values with standard deviations (in parentheses) of two acoustic features
(build-up and climax) of pant-hoots in five individuals each of the Budongo and Gombe
populations, and mean values for the two populations (from Wong 1995: 44).
Parameter Population
measured
Budongo Gombe
DN MG CH MA TK —X FD GB BE FR PF —X
Build-up
Rate of delivery 2.62 2.49 1.51 2.21 2.80 3.17 3.46 3.16 3.15
(elements/second) (1.3) (1.2) (1.3) (0.9) (0.9) (0.4) (0.8)
Duration (seconds) 0.41 0.42 0.48 0.54 0.46 0.36 0.22 0.25 0.24 0.27
(0.2) (0.1) (0.3) (0.3) (0.3) (0.0) (0.0) (0.0)
Fundamental 635 589 649 774 662 498 486 445 691 530
frequency (Hz) (347) (250) (178) (665) (242) (256) (7.4) (15)
Climax
Duration (seconds) 0.79 0.71 0.94 0.48 0.58 0.70 0.59 0.76 0.76 0.66 0.98 0.75
(0.3) (0.1) (0.1) (0.1) (0.2) (0.1) (0.1) (0.1) (0.1) (0.1)
Minimum frequency 718 656 583 592 578 625 643 809 539 730 577 660
(Hz) (143) (119) (183) (188) (66) (165) (194) (142) (280) (19)
Maximum frequency 1308 1268 1040 1230 1250 1219 1163 1425 1100 1388 1056 1226
(Hz) (247) (253) (287) (105) (66) (257) (272) (413) (218) (291)
Frequency range 565 613 456 633 672 588 520 616 561 659 479 567
(Hz) (174) (149) (107) (76) (133) (159) (138) (271) (63) (310)
Average fundamental 1001 969 831 874 958 927 941 1115 819 1110 769 951
frequency (Hz) (217) (203) (186) (141) (155) (233) (231) (332) (148) (96)