Mammals consumed by bonobos (Pan paniscus): new data from the Iyondji forest, Tshuapa, Democratic Republic of the Congo.

Findings of regional variations in the behavioral patterns of non-human primates have led to the vigorous study of animal traditions (or culture), which contribute to a biological understanding of diversity in human cultures. Although our knowledge of behavioral variations of the bonobo (Pan paniscus) is limited compared with its sister species, the chimpanzee (P. troglodytes), variations in the prey of this species have been reported across study sites. This study describes evidence of mammals consumed by bonobos in the Iyondji site, which was established in 2010. We found evidence that Iyondji bonobos consumed duikers (Cephalophus dorsalis, C. monticola) and diurnal monkeys (Cercopithecus ascanius), which is notable because only anomalures (Anomalurus spp.) are consumed by bonobos in Wamba, a long-term study site established in 1973, located in an area adjacent to Iyondji. Moreover, bonobos do not transfer between the two populations due to the river between the sites. According to our census of duikers and diurnal monkeys, Iyondji bonobos appeared to encounter diurnal monkeys more frequently than did Wamba bonobos. Although humans have apparently had a more pronounced impact on the habitats in Wamba than on those in Iyondji, it remains unclear how such environmental conditions may have contributed to the differences in the prey consumed by bonobos in different sites. Our findings suggest that additional research at various sites could reveal the nature of the variations in the behavior of bonobos.

Habitat use of bonobos (Pan paniscus) at Wamba: Selection of vegetation types for ranging, feeding, and night-sleeping.

Understanding the habitat requirements of great apes is essential for effective conservation strategies. We examined annual habitat use of a bonobo group in the Wamba field site within the Luo Scientific Reserve, Democratic Republic of the Congo. Using satellite imagery, we categorized the group's ranging area into three forest types: (1) primary and old secondary forest (P/OS), (2) young secondary forest and agriculture (YS/Ag), and (3) swamp forest (Sw). We tracked the group for 1 year (2007-2008) and compared usage of the three forest types for ranging, feeding, and night-sleeping. We also recorded what the bonobos ate and monitored monthly fruit availability in each forest type. The group ranged and fed more often in P/OS and less often in YS/Ag and Sw than expected based on habitat availability. Also, the group slept mostly in P/OS (94% of nights monitored), but also in YS/Ag (1%), and Sw (5%). Fruit availability in P/OS had no significant effect on habitat selection, but the group fed in YS/Ag most often during the two months when fruits in P/OS were least abundant. In June, when fruit of Uapaca spp. (selectively eaten by bonobos) was generally abundant in Sw, the group mostly ranged and slept there. The bonobos fed most often on herbaceous plants in all three forest types. In Sw, the bonobos frequently ate mushrooms. Our results show that semi-open forest with abundant herbaceous plants such as YS/Ag could be an important feeding habitat and may provide fallback food for bonobos when fruits are scarce. Furthermore, Sw can serve seasonally as a main habitat to complement P/OS if adequate food resources and tree nesting opportunities are available. We conclude that bonobos use diverse habitats depending on their needs and we highlight the importance of minor-use habitats for sustaining populations of target species in conservation planning.

Contrasting responses of web-building spiders to deer browsing among habitats and feeding guilds.

We examined web-building spider species richness and abundance in forests across a deer density gradient to determine the effects of sika deer browsing on spiders among habitats and feeding guilds. Deer decreased the abundance of web-building spiders in understory vegetation but increased their abundance in the litter layer. Deer seemed to affect web-building spiders in the understory vegetation by reducing the number of sites for webs because vegetation complexity was positively correlated with spider density and negatively correlated with deer density. In contrast, the presence of vegetation just above the litter layer decreased the spider density, and deer exerted a negative effect on this vegetation, possibly resulting in an indirect positive effect on spider density. The vegetation just above the litter layer may be unsuitable as a scaffold for building webs if it is too flexible to serve as a reliable web support, and may even hinder spiders from building webs on litter. Alternatively, the negative effect of this vegetation on spiders in the litter may be as a result of reduced local prey availability under the leaves because of the reduced accessibility of aerial insects. The response to deer browsing on web-building spiders that inhabit the understory vegetation varied with feeding guild. Deer tended to affect web-invading spiders, which inhabit the webs of other spiders and steal prey, more heavily than other web-building spiders, probably because of the accumulated effects of habitat fragmentation through the trophic levels. Thus, the treatment of a particular higher-order taxon as a homogeneous group could result in misleading conclusions about the effects of mammalian herbivores.