Graphical Abstract Highlights d Bonobos and gorillas had stronger looking impulses compared to chimpanzees d Young apes looked longest at camera traps compared to mature individuals d Presence of a research site or conspecifics reduced the duration of looking d Both social and environmental factors affect great ape curiosity in the wild In Brief Kalan et al. use a large-scale field experiment to assess the reaction of wild great apes toward a novel object: camera trap devices. Bonobos show the strongest looking impulse and are more neophobic than either gorillas or chimpanzees. Additional social and environmental effects on reactions demonstrate the complexities of animal curiosity.

Habitat loss and hunting threaten bonobos (Pan paniscus), Endangered (IUCN) great apes endemic to lowland rainforests of the Democratic Republic of Congo. Conservation planning requires a current, data-driven, rangewide map of probable bonobo distribution and an understanding of key attributes of areas used by bonobos. We present a rangewide suitability model for bonobos based on a maximum entropy algorithm in which data associated with locations of bonobo nests helped predict suitable conditions across the species' entire range. We systematically evaluated available biotic and abiotic factors, including a bonobo-specific forest fragmentation layer (forest edge density), and produced a final model revealing the importance of simple threat-based factors in a data poor environment. We confronted the issue of survey bias in presence-only models and devised a novel evaluation approach applicable to other taxa by comparing models built with data from geographically distinct sub-regions that had higher survey effort. The model's classification accuracy was high (AUC = 0.82). Distance from agriculture and forest edge density best predicted bonobo occurrence with bonobo nests more likely to occur farther from agriculture and in areas of lower edge density. These results suggest that bonobos either avoid areas of higher human activity, fragmented forests, or both, and that humans reduce the effective habitat of bonobos. The model results contribute to an increased understanding of threats to bonobo populations, as well as help identify priority areas for future surveys and determine core bonobo protection areas.Additional co-authors: Omari Ilambu; Bila-Isia Inogwabini; Innocent Liengola; Albert Lotana Lokasola; Alain Lushimba; Joel Masselink; Valentin Mbenzo; Norbert Mbangia Mulavwa; Pascal Naky; Nicolas Mwanza Ndunda; Pele Nkumu; Valentin Omasombo; Gay Edwards Reinartz; Robert Rose; Tetsuya Sakamaki; Samantha Strindberg; Hiroyuki Takemoto; Ashley Vosper; Hjalmar S. Küh

Maternal cannibalism, whereby a mother consumes her own offspring, occurs in various animal taxa and is commonly explained by nutritional stress or environmental pressures. It is rare in nonhuman primates and is considered an aberrant behavior only observed under high-stress conditions. It was therefore surprising when, in the first reported case of cannibalism in wild bonobos, a mother consumed part of the dead infant at LuiKotale. Here we report two more cases of maternal cannibalism by wild bonobos at two different study sites, Wamba and Kokolopori. The dead infants' mothers participated in the cannibalism in both cases. At Kokolopori, although the mother did consume part of the carcass, it was held and shared by another dominant female. At Wamba, the mother was a dominant female within the community and was the primary consumer of the carcass. In both cases, cannibalism resembled other meat-eating events, with the dominant female controlling meat consumption. Infanticide was not observed in either case, but its occurrence could not be ruled out. Although rare, the occurrence of maternal cannibalism at three different study sites suggests that this may represent part of the behavioral repertoire of bonobos, rather than an aberrant behavior.

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We compared the feeding ecology of the Hali-Hali community of bonobos (Pan paniscus) at Kokolopori, a new field site in the Democratic Republic of the Congo, between two periods 5 months apart. During the first study period (SP1), bonobos relied heavily on the dry seeds of Guibourtia (Caesalpiniaceae), mostly eaten from the ground. The second period (SP2) was characterized by high consumption of ripe tree fruit. Terrestrial herbaceous vegetation (THV) contributed little to the diet in either study period. The low amount of ripe fruit and the high reliance on seeds in the diet during SP1 were associated with high cortisol production and low levels of urinary C-peptide in females, suggesting nutritional stress. However, female gregariousness was not constrained during the fruit-poor period, probably because high seed abundance on the ground ameliorated scramble feeding competition. This is the first description of extensive seed predation by bonobos. It suggests that bonobo feeding ecology may be more similar to that of chimpanzees than previously recognized.