Moving in a Miombo: Ranging Patterns and Habitat Use in Red-Tailed Monkeys (Cercopithecus ascanius) From the Issa Valley, Tanzania.

OBJECTIVES Guenons are a valuable model for understanding primate adaptability to heterogeneous habitats, similar to the environmental pressures faced during hominin evolution. This study investigates how red-tailed monkeys (Cercopithecus ascanius) use two distinct vegetation types, riparian forests and miombo woodlands, within a mosaic habitat in the Issa Valley, Tanzania. We assessed how seasonality impacts core area sizes in both vegetation types, the proportion of spatial overlap between core areas across different seasons and years, and whether woodland use is associated with increased daily path lengths (DPLs) or specific foods.

METHODS We employed kernel density estimates on behavioral observations (2016-2023) to calculate core area sizes and overlaps and linear regressions to assess relationships between woodland use and DPL. We employed logistic regression to analyze associations between food categories and woodland use.

RESULTS Core area sizes and overlaps did not vary significantly between seasons in either woodlands or forests. DPL showed a trend toward being lower on days when animals spent more time in woodland. Feeding on bark, flowers, and unripe fruit strongly increased the likelihood of woodland use, whereas ripe fruit was associated with forests.

DISCUSSION We propose several drivers for woodland use as well as what role niche partitioning with sympatric primates may play. Our study indicates that this arboreal primate dynamically utilizes the vegetation matrix, highlighting the importance of behavioral flexibility for Plio-Pleistocene hominins as forests were gradually replaced with wooded landscapes.