Time and distribution: a model of ape biogeography

We use data from 20 chimpanzee, bonobo and gorilla study sites to develop an African great ape time budgets model to predict the animals' capacity to survive in a range of habitats across sub-Saharan Africa. The model uses body mass and climatic data to predict the time animals must allocate to key activities (feeding, moving, resting and social interaction), and then uses these to assess the limiting group size that could be sustained in a particular habitat. The model is robust against changes in minimum cut-off values, and predicts the current biogeographic distributions of the two African ape species remarkably well. Predicted group sizes for Parr and Gorilla are close to observed averages. The model also indicates that moving time plays a crucial role for both Pan and Gorilla site presence: i.e. at sites where they are absent it is primarily moving time that is increased as compared to other time budget variables. Finally, the model demonstrates that Pan and Gorilla distributions and group sizes can be accurately modelled by simply modifying the body mass variable, indicating that both share a similar underlying ecological bauplan.