Uchikoshi / Poster

Behavioral development of gibbon infants (Hylobates agilis)

Makiko Uchikoshi, Toshiaki Mizutani and Tetsuro Matsuzawa
(Primate Research Institute, Kyoto University)

     There have been very few studies concerning behavioral development of gibbons. In the present study, we longitudinally observed the behavioral development of two hand-reared agile gibbon infants. They are sons of the same couple.(elder:Tsuyoshi,younger:Raja) Although we still continue the observation, here we report the first 16 month of life for Tsuyoshi, and the first 4 month of life for Raja. The characteristics of gibbon behavior were investigated by comparing the data collected with those on other primates from previous studies. The results show the following points. (1)The ages of deciduous teeth eruption were similar to those of macaques. The results show that the growth pattern in early stage is more similar to those of macaques than those of other apes. (2)Species-typical behavioral patterns about position, locomotion, and object-manipulation appeared significantly later in gibbons than in macaques, and these appeared still earlier in gibbons than in chimpanzees. This means that gibbons stands in the middle between macaques and chimpanzees. (3)Tsuyoshi started brachiation?a species-typical locomotion, from the27th week of age. The brachiation increased gradually over time. They rarely walked on the ground by quadre-peddally. At the 35th week of Tsuyoshi, the hanging behavior appeared about 70 percent of the total frequency of locomotion.