West side story: regional inter‐troop variation in baboon bark‐stripping at gorongosa national park, Mozambique

Objectives: Baboons possess sophisticated physical and social cognitive abilities; hence, the lack of evidence to date of largescale behavioral variation in these primates is puzzling. Here we studied a candidate for such variation—the stripping of bark from Acacia robusta trees for consumption of the sap and soft tissue underneath—in Gorongosa National Park, Mozambique. Materials and Methods: We surveyed an area inhabited by ~60 troops of chacma baboons, recording the availability and characteristics of the target trees, as well as the presence or absence of bark-stripping at 45 habitat plots distributed across a grid covering an area of ~300km2. Results: Camera traps confirmed the presence of baboons at all habitat plots, and we identified regional clumping in the distribution of the behavior, a pattern consistent across two consecutive years. Proportion and mean height/width of A. robusta did not predict whether bark-stripping behavior was present at a given site, nor did broader ecological variables such as habitat type and distance to the nearest water source. However, stripping sites had significantly higher numbers of A. robusta than non-stripping sites, and within a given bark-stripping site, baboons preferred to strip taller and wider trees among those available. Discussion: The prominent geographical clustering we uncovered may have been driven by opportunity (i.e., the prevalence of A. robusta at a given site), but is also consistent with a possible (non-mutually exclusive) cultural interpretation. We propose avenues for future research on Gorongosa's baboons to better quantify the relative contributions of ecology, genetics, and social.