Reassessment of age of sexual maturity in gibbons (hylobates spp.)

Abstract

From studies of both wild and captive animals, gibbons are thought to reach sexual maturity at about 6 to 8 years of age, and the siamang (Hylobates syndactylus) at about 8 to 9 years. However, a review of the literature reveals that in most cases the exact age of the maturing animals was not known and had to be estimated. This study presents seven case reports on captive gibbons of known age. Captive males of the white-cheeked crested gibbon (H. leucogenys leucogenys) and of the siamang (H. syndactylus) can breed at the age of 4 and 4.3 years, respectively. Similarly, hybrid females (H. lar x H. moloch) and siamang females can breed at 5.1 and 5.2 years, respectively. This finding may help to improve the breeding success of captive gibbon populations. It is not clear whether gibbons reach sexual maturity earlier in captivity or whether sexual maturity is also reached by five years of age in the wild. Possible implications for the interpretation of group size regulation and of reproductive strategies of wild gibbons are discussed.

Longitudinal study of delayed reproductive success in a pair of white‐cheeked gibbons (Hylobates leucogenys)

“…In accordance with recommendations from the Gibbon SSP s , Lincoln Park Zoo (LPZ), Chicago, Illinois, introduced a pair of young whitecheeked gibbons in 1995, with hopes that the pair would also propagate successfully. Gibbons are reported to reach sexual maturity between 6 and 8 years of age, although captive male white-cheeked gibbons may produce offspring as early as 4 years of age [Geissmann, 1991]. When she was introduced in 1995, the female gibbon in the current study was 6.5 years old and the male was 5 years of age.…”

“…Although we did not score any increases in sexual or prosocial behavior during data collection, we did observe several complete copulations outside of the observation sessions. The female [Geissmann, 1991], indicates she conceived approximately 7-8 calendar months after moving to the exclusively indoor exhibit.…”

Hormonal Correlates of Paternal Care Differences in the Hylobatidae

“…Native to Southeast Asia and parts of India and China, the hylobatids comprise the largest group of apes consisting of four genera (Nomascus, Hylobates, Symphalangus, and Hoolock) [Groves, 2001]. All species are believed to be primarily monogamous, form long-lasting pair-bonds, and are typically found in small family groups with one to four offspring [Brockelman et al, 1998;Geissmann, 1991;Leighton, 1987;Macdonald, 2001;Reichard and Barelli, 2008]. Yet, extra-pair copulations have been reported in some hylobatid populations, suggesting that social bonds and reproductive strategies may be more dynamic than originally reported [Palombit, 1994a[Palombit, ,b, 1996Reichard and Barelli, 2008].…”

Social dynamics modify behavioural development in captive white-cheeked (Nomascus leucogenys) and silvery (Hylobates moloch) gibbons

“…The estimated life span of gibbons varies between 20 and 40 years (Palombit 1995), with a reported longevity maximum in captivity of 60 years (Geissmann et al 2009), and females produce a single offspring every 2-5 years (Palombit 1995). Both captive and wild gibbons appear to reach sexual maturity by 8 years of age (Geissmann 1991), but sexual maturation occurred before 5 years of age in several captive gibbons that were removed from their natal groups and housed with an older mate (Geissmann 1991). This indicates some social influence on development.…”