flailing branches,throwing rocks or other loose material,slapping the
ground with hands,stomping with feet,hitting or stamping at a tree
(drumming display),seizing branches and swaying them vigorously from
side to side,or showing exaggerated leaps or brachiation in a tree
(Goodall 1986).Pant-hoots conclude with a let-down portion,which
includes unmodulated tonal elements of low frequency,similar to those
of the build-up.
Pant-hooting is given in several contexts,including in response to other
pant-hooting individuals,after rejoining other community members,in
response to strange conspecifics,on arriving at a particularly rich food
source,during agonistic displays,on capturing prey items,and during the
night.It can be heard over long distances and its functions have been
hypothesized to include long-range announcement of an individual’s
presence and sex,hence mediating interindividual spacing among some
individuals and groups,and reunion of others.In bonobos (P.paniscus),
apparently homologous vocalizations are known under the term hooting
complex and occur in similar contexts as pant-hooting of common chim-
panzees (de Waal 1988).
Characteristics of these great ape calls resembling at least some gibbon
songs (especially female great calls) include loudness,a hypothetical
function in long-distance interindividual or intergroup communication
(all species),acceleration of note rhythm (common in chimpanzees and
gorillas,apparently absent in orangutans),a final slow-down in rhythm
(chimpanzees),higher intensity in the central section of the call (appar-
ently in all species of great apes,but variable in orangutans),biphasic
notes consisting of alternating exhalation and inhalation (absent in goril-
las),higher frequency in the central section of the call,pure tone of
notes (most prominent in chimpanzees),and frequent accompaniment
with piloerection and a locomotor display that may include leg kicking,
stomping,branch shaking,vegetation slapping or throwing,jumping,
running,chest beating,or ground thumping.
Among members of Old World monkeys,too,certain vocalizations can
be discerned that resemble some elements of the gibbon song (great
call) in function and to some degree in structure.In many species these
characteristics are restricted to loudness and a hypothetical function
in long-distance interindividual or intergroup communication (Vogel
1973;Horwich 1976;Tilson and Tenaza 1976;Waser 1977,1982;Oates and
Trocco 1983;Herzog and Hohmann 1984;Hohmann and Herzog 1985;
Gautier 1988).Other characteristics mentioned above are frequently
absent.In many species (Cercocebus spp.,Lophocebus spp.,Macaca
silenus,Papiospp.,Presbytis potenziani,P.thomasi,Simias concolor,
Trachypithecus spp.) the occurrence of biphasic notes consisting of
alternating exhalation and inhalation has been reported.In some species116 Thomas Geissmann