Comparative behavior of gibbons and siamangs

Includes bibliographical references (pages 98-100)To test the hypothesis that a relationship exists between daily behavior patterns and genera of Hylobatidae, a ten month observation of three captive groups of hylobatids (hylobates lar at Busch Gardens, Hylobates concolor at the Los Angeles Zoo, and Symphalangus syndactylus also at the Los Angeles Zoo) was begun in May, 1975, and terminated in February, 1976. Qualitative observations, which were made intensively for the first two months and intermittently thereafter, were used to construct a checklist for quantitative analysis. The original twenty-three behavior categories on the checklist were collapsed into eight general categories for statistical intergroup comparisons: resting, play, feeding, aggregate, brachiation, bipedalism, and grooming. The frequency of behavior for each group for each behavior category at one hour intervals was totaled and mean scores were calculated and graphed to illustrate species behavior profiles.\ud The eight behavior categories were further reduced to a selected three behaviors, rest, play, and feeding, in order to conform to the assumptions of the multivariate analysis of variance (MANOVA) model used to analyze these data. Quantitative observations of these three behaviors were divided into early day and late day frequencies and compared on that basis to test the hypotheses of no significant differences among the three groups of hylobatids.\ud The behavior of the siamang was qualitatively distinguishable from the two species of gibbons. The gibbons showed generally higher levels of activity and markedly more agile bipedalism. The multivariate analysis of variance indicated that there was a significant difference between gibbons and siamangs in feeding behavior, a significant difference between Hylobates lar and Hylobates concolor in play behavior, but no significant difference among the three groups in resting behavior