抄録
Gibbons stand between old world monkeys and great apes in phylogeny. Gibbons have some unique features including relatively small body, and singing behavior. We still poorly understand how gibbons acquire their uniqueness in ontogeny. To collect data on gibbon development, two male agile gibbons (Hylobates agilis) born at Primate Research Institute of Kyoto University were observed from birth to adulthood. Dentition, body weight, and sexual maturation were observed and recorded under body growth. The age at which each behavioral pattern was first observed was recorded and compared with those from previous studies on other primates. Results can be summarized as follows. The ages of individual teeth eruptions in gibbons were similar to those of Japanese macaques, but occurred earlier than in chimpanzees and humans. However, the ages at which most common behavioral patterns were first observed in gibbons were later than those of Japanese macaques, but earlier than those of chimpanzees and humans. Several behaviors (e.g., combinatory object manipulation) appeared later in gibbons than in chimpanzees and humans. Singing, a unique gibbon behavior, started from only 2 weeks of age, while sexual differentiation in song repertoire occurred around puberty. There was no adolescent growth spurt in body weight. Considering these results, the developmental process of gibbons seems to be connected to phylogeny and species-specific features. Observations on additional individuals are required to confirm the generality of this study’s results.
