Abstract # 2206:

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Assessing the Classification of Immature Life History Stages in Gorillas

J. E. Hutchinson and A. W. Fletcher
University of Chester, Dept.of Biological Science, Parkgate Road, Chester, Cheshire, United Kingdom
     Many behavioral studies of immature primates use markers to indicate progression in ontogenic development. Such markers of the infant, juvenile, adolescent and adult periods are often defined by categorical age, rather than behavioral, physical or physiological traits, and are frequently applied between related species. Recent life history research indicates that developmental trajectories are flexible entities, which differ with species, environment and sex. Thus the use of structured markers to determine life stage invariably leads to rigidity in a dynamic system, hampering the understanding of life history strategies. Here we test four published categorizations of life-stage (derived from Gorilla beringei beringei) using behavioral data from captive western gorillas (G. gorilla gorilla). Behavioral data were collected from 13 male (3-11 years old) and 9 female (3-8 years old) captive immature western gorillas housed in 5 family groups, using continuous focal sampling; 900 hours of data were collected over 131 days. Five behavioral variables were identified that illustrate changes in immature Gorilla behavior. Using repeated measures ANOVAs the concordance of published categorisations to behavioral variables ranged from 40-70%, but rose when markers were adapted for the captive western gorilla using discriminative analysis. Considerable variance in life history strategies within the genus gorilla is not reflected in currently used life stage categorizations. Thus, the use of flexible species-specific classifications within immature primate studies, based on easily observed behavior, will reveal variability within ontogenic trajectory.