Exerpt

[...] Wamba is one of the few study sites where this has been addressed for decades. In the 1980s, Kano and Mulavwa (1984) conducted behavioral observations of bonobos and classified the vegetation of Wamba into primary forest, aged secondary forest, young secondary forest, secondary shrub, and swamp forest using a hand-drawn map. Based on observations over several years, they found that bonobos used primary, secondary, and swamp forest, and that they prefer fruits, especially those of Dialium spp. and Landolphia owariensis, which make up a significant proportion of their seasonal diet. They suggested that resource availability and relative preference might affect the seasonal variation in their diet.
In the 1990s, Idani et al. (1994) obtained more detailed information on the vegetation of Wamba, listing the local and scientific names of more than 500 plant species in Wamba and indicating which ones provide bonobo food. The list has been the main reference for identifying the plant species in Wamba. They also identified the dominant tree species in the vegetation of primary, young secondary, and swamp forests and found that most provide bonobos with food (such as fruits and leaves). They also noted the abundance of herbaceous and vine fruits in those forest types, indicating that the entire habitat in Wamba is rich in various food resources for bonobos.
Following this, Hashimoto et al. (1998) created a map similar to that drawn by Kano and Mulavwa (1984) in a more objective, continuously monitorable manner using satellite imagery. By layering location data from several months of tracking a bonobo group continuously on that map, they also showed that bonobos generally use primary, young secondary, and swamp forest quantitatively. The results showed seasonal variation in range: the bonobo group used primary forest more frequently during the rainy season when fruits are abundant there.
In the 2010s, Mulavwa et al. (2010) focused on habitat use for night sleeping and, based on data from 2 years of tracking a bonobo group, found that bonobos in Wamba sleep in swamp forest at night more frequently than previously thought, especially when their favorite fruit is abundant there. The study also suggested the importance of re-evaluating the value of swamp forest for bonobos.
Following these studies, we investigated the annual habitat use of a group of bonobos in Wamba, focusing on their habitat selection for ranging, feeding, and night sleeping (Terada et al. 2015; Nackoney and Terada 2023). We found that when fruit availability is low in primary forest, the group feeds more frequently in secondary forest, where they feed mainly on herbaceous vegetation. During the months when they sleep mainly in swamp forest, they mainly range and feed there. Less-used habitats, such as anthropogenic habitats and swampy areas, enhance the heterogeneity of habitats within their range, providing the bonobo groups with a wider range of resource options.
Other bonobo study sites are also dominated by non-inundated primary forest, with secondary forest and inundated areas such as swamp forest and grassland occupying a portion of the supplemental range; nevertheless, bonobos are also present where inundated areas are dominant (Terada et al. 2018). Although the frequency with which bonobos use inundated habitats appears to be highly dependent on the availability of those habitats within the potential range, comparative studies among study sites using uniform survey methods are needed to provide a clear answer to this. [...]