Chimpanzees use advanced spatial cognition to plan least-cost routes

While the ability of naturally ranging animals to recall the location of food resources and use straight-line routes between them has been demonstrated in several studies, it is not known whether animals can use knowledge of their physical landscape to plan least-cost routes. This ability is likely to be particularly important for animals living in highly variable energy landscapes, where movement costs are exacerbated. Here, we used least-cost modelling to investigate whether chimpanzees (Pan troglodytes) living in a rugged, montane environment use advanced cognitive skills to plan energy efficient routes. We used a subset of chimpanzee movement segments together with the available laboratory measurements of chimpanzee energy expenditure to assign movement costs which were incorporated in an anisotropic least-cost model and straight-line null model. The least-cost model performed better than the straight-line model across all parameters, and linear mixed modelling showed a strong relationship between the cost of observed chimpanzee travel and predicted least-cost routes. To our knowledge, our study provides the first example of spatial memory for landscape and the ability to plan least-cost routes in non-human animals. These cognitive abilities may be a key trait that have enabled chimpanzees to maintain their energy balance in a low-resource environment. Our findings provide a further example of how the advanced cognitive complexity of hominids have facilitated their adaptation to a variety of environmental conditions and lead us to hypothesise that landscape complexity may play a role in shaping cognition.