Bonobos, Pan paniscus, in the forest-savannah mosaics of West DR Congo: does spatial structure influence the forest use dynamics?

Bonobos, Pan paniscus, are endemic to the Democratic Republic of Congo (DRC) but the species’ range is still not precisely known. For example, the populations from West DRC have only been identified in 2005, following inventories conducted by WWF. This region is characterized by a forest-savannah mosaic, a particular ecotone with naturally fragmented forests, in which bonobos have hardly ever been studied in comparison with those evolving in central DRC rainforests. The area also increasingly includes numerous anthropogenic activities including logging and cattle ranching. Effective long-term conservation programs are then essential for the survival of bonobos’ populations. We decided to focus our study on bonobos’ forest use dynamics, testing spatial structure influence on bonobos’ density and forest use. This hypothesis is based on a landscape ecology theory, the pattern-process paradigm, establishing a triangular link between the structure, the composition and the ecological processes of a landscape. We used the interior-to-edge ratio to classify our study area (200km² of forests) in 5 categories of forest patches: (i) corridors (0.1 to 5.5km², ratio of 0), (ii) small patches (3.4 to 4.3km², ratios between 0.23 and 0.33), (iii) middle patch with edge area predominant (13.8km², ratio of 0.7), (iv) middle patch with interior area predominant (22.3km², ratio of 1.17), (v) big patch (122.2km², ratio of 1.43). We walked transects (total effort: 126km) to identify habitats (landscape composition) and bonobos’ use indices (nests and food remains – landscape ecological process). Results unexpectedly showed that bonobos use all forest patches, even corridors, mostly used for feeding. Small patches even include higher nest density than the big patch. Moreover, habitats with predominant Marantaceae understory are correlated with higher nest density. The study is still in process and sampling areas will be increased in further field work. The first results however already indicate that we could elaborate a model predicting bonobos’ presence according to habitats and spatial structure and designate forest patches to protect as a priority. This information should allow formulating specific management recommendations for regional conservation programs and logging concessions