Ontogeny of positional behavior and support use among Colobus angolensis palliatus of the Diani Forest, Kenya

In this project I studied black and white colobus monkeys (Colobus angolensis palliatus) inhabiting the Diani Forest of south coastal Kenya to test whether activity budgets, positional behavior, and support use differed among individuals in three age categories (juveniles, subadults, and adults). Data for three habituated groups were collected from June to August 2012 and from May to July 2014. Instantaneous sampling and pooled data were used to create overall behavior profiles for the three age categories. Activity budgets differed significantly among the categories. Adults rested more and moved less, subadults socialized more, and juveniles moved more often than individuals in the other two age categories. Support use differed, with juveniles and subadults accessing smaller supports more frequently (i.e., juveniles: bough 19.4 %, branch 57.9 %, twig 13.5 %; subadult: bough 18.6 %, branch 64.5 %, twig 8.2 %) whereas adults preferred larger supports (i.e., adults: bough 32.1 %, branch 54.0 %, twig 5.3 %). Despite different support use, locomotor profiles were remarkably consistent among age categories (i.e., ranges: quadrupedal walk 35.0-45.2 %, bound 17.5-25.3 %, climb 11.2-22.7 %, leap 15.1-19.9 %). Sitting was the predominant posture, accounting for 89.5-92.5 % of the posture observed for all age categories. Overall positional profiles of adults and subadults were statistically indistinguishable whereas juveniles differed significantly from adults but not from subadults. It is hypothesized that the different frequency of specific locomotor behaviors, for example bounding, is attributable to morphological changes associated with ontogeny. Nonetheless, these findings support the notion that primates achieve adult-like positional behavior competence during the juvenile life stage.