Longitudinal patterns of reproduction in wild female siamang ( Hylobates syndactylus ) and white-handed gibbons ( Hylobates lar )

摘要: I present the 6- year reproductive histories of three wild female siamang (Hylobates syndactylus)and four white-handed gibbons lar)at Ketambe Research Station (Sumatra, Indonesia). Reproductive output varied considerably among females. Two females failed to gestate: both were nulliparous young adult H. lar,one which remained unpaired for 4 years after dispersing from her group, while other lost recently acquired mate another female. Only one- (a gibbon)- gave birth more than once, yielding interbirth intervals 22 and 31 months. Pair bond stability or reduced interspecific feeding competition factors may have contributed brevity these intervals. The females- one lar,and syndactylus-each suggesting minimum exceeding 4–5 (H. lar)and 3 syndactylus)in individuals. Even given pronounced variation observed lar,these data suggest that often exceed 2- 3- interval commonly attributed two species. Sources failure 1) maternal abandonment neonate due impaired ability provide care syndactylus,),(2) premature stillbirth syndactylus,),and (3) pregnancy termination lar).These a review information on longevity age at menarche actual lifetime gibbon fall far short 10 offspring/lifetime originally proposed Indeed, rear as few five offspring weaning in lifetime, is figure reminiscent potential some pongids. Finally, variance success higher expected monogamous species, suggests (and males) are under strong selective pressure exert choice, possibly through acquisition (new) mates extrapair copulations. Future research must clarify availability opportunities paired adults engage sociosexual behaviors.