Hylobates agilis (and H. albibarbis)
Short phrases consisting of simple hoots, more complex hoots ("whoo-aa") and bi-phasic hoots are uttered by males and females. Bi-phasic hoots consist of notes alternatingly produced during exhalation and inhalation ("whoo-aa"). Some males were heard to produce relatively soft, squealing sounds between their short phrases, similar to males of H. muelleri. Female great call consisting of long notes of modulated frequency. A first, often very weak climax in frequency is reached at the beginning of the great-call; a second, more pronounced climax of higher frequency notes occurs near the end of the great call. Male produces coda. Male solo song bouts and duet song bouts.
No clear vocal differences are known to occur between the agile gibbon (Hylobates agilis) and the white-bearded gibbon (H. albibarbis).
a. Male short phrases (Twycross Zoo, United Kingdom, 2 Oct. 1988; and Guangzhou Zoo, China, 7 Sept. 1990)
b. Great-call sequnce consisting of female great-call with male contribution (Asson Zoo, France, 31 May 1988)
|Solo song, adult mated male, Dortmund Zoo, Germany,
20 June 1987.
Produced right after dawn. This male is mated with a female H. muelleri.
|Solo song, adult mated male "Sebastian",
Twycross Zoo, U.K., 2 Oct. 1988.
This song began as a duet song, after which the male kept singing alone for more than 30 minutes.
|Solo song, adult solitary male, Guangzhou Zoo, U.K.,
7 Sept. 1990.
This male probably is H. albibarbis.
|Duet song, adult pair "Tout Petit" and "Singa",
Asson Zoo, France, 31 May 1988.
Several other gibbons also sing in the background, most prominently a hybrid female H. pileatus x H. lar and a male N. leucogenys.
|Duet song, adult pair "183/1A" and "183/2A",
Paignton Zoo, U.K., 21 Oct. 1988.
A female H. moloch also sings in the background.
|Solo song, adult mated female, Louisiana Purchase Garden,
Monroe, U.S.A., Sept. 1979 (rec. Charles Welch).
This female was kept with a male (H. muelleri) and their hybird daughter. The male of the mixed pair contributed a few squeals to the song bout. The hybrid daughter produced several great-calls in synchrony with her mother, but not in this example.