Lira Yu^{1, 2}, Boniface Zogbila³ & Tetsuro Matsuzawa<sup>1

1.</sup> Primate Research Institute, Kyoto University, Japan
^2. Japan Society for the Promotion of Science
^3. Institut de Recherche Environmentale de Bossou

Bossou chimpanzees have shown low rates of meat consumption compared to other communities (Sugiyama & Koman 1987; Hockings et al. 2012). Therefore, the addition of data describing their prey repertoire is imperative for ecological and behavioral studies at this site. Here, we report a novel observation of bird consumption by one adult female chimpanzee in the Bossou community.

Behavioral observations were conducted at Bossou, one of the long–term research sites for chimpanzees located at the south–east corner of the Republic of Guinea, West Africa (Matsuzawa et al. 2011). The core area used by Bossou chimpanzees includes approximately 6 km², dominated by primary and secondary forest and surrounded by cultivated or abandoned fields and shrub forest. Consumption of the wild bird was observed by LY and BZ, who recorded all behavioral occurrences during the event ad libitum.

On October 30, 2012, at 7:39 AM, we (LY and BZ) observed four adult chimpanzees (JJ, TA, FF, and Jr) in the forest. At 7:47 AM, three adult male chimpanzees (JJ, TA, and FF) started to move. However an adult female chimpanzee Jr (estimated to be 54 years old) remained. For approximately ten minutes, Jr showed no movement. At 7:57 AM, shrubs began to rustle. We heard a typical call of coucal (a bird belongs to cuckoo family) from a nearby bush. The call consists of a series of ‘hoos' which at first increase in rate and volume and die away at the end (Serle et al. 1990). A few seconds later, Jr suddenly moved toward the bush. We saw Jr capturing two nestlings at once from a nest that had been constructed in the bush and located ca. 2 meters above the ground. Jr walked a few steps away holding the two nestlings one in each hand and sat on the ground. Jr started to take a bite of the nestling in her left-hand. Then Jr put the remainder of the nestling on the ground and consumed a few leaves from a nearby liana. We (BZ and TM) later identified the leaves as Clerodendrum silvanum. This liana is characterized by its needle-like spines that are derived from young stems and petioles but not on epidermis (Hawthorne & Jongkind 2006). For the next few minutes, the nestling and leaves were consumed in an alternating manner. Only the left–hand was used during consumption of both items, while the right–hand continued to hold the other nestling. At 8:07 AM, Jr stopped eating and put what remained of the consumed nestling on the ground. Jr stood up bipedally, moved a few steps and started slapping the other nestling on the ground. The nestling emitted some vocalizations when it hit on the ground. In response, Jr released the nestling from her hand and stepped back. Soon, Jr took the nestling again and continued to slap it on the ground. After several cycles of slapping and stepping away from the nestling, Jr picked the nestling up and moved out of sight.

At 9:09 AM, after we lost track of Jr, we returned to the bush and discovered a bird carcass on the ground amid scattered leaves that had been consumed (see Figure 1). We assumed this carcass was the first nestling that Jr consumed because it lacked some body parts; its head and legs were missing from the carcass while most of the body trunk remained intact. We could not find any detached body parts in the vicinity of the carcass, suggesting that these had all been consumed by Jr. Because of the emitted call and the carcass, it was identified as the black–throated coucal (Centropus leucogaster), a species of cuckoo family (Cuculidae). While cuckoos are known to be parasitic in their nest habits, coucals construct their own nests and rear their young (Serle et al. 1990).

This is the second confirmed species of bird preyed upon by Bossou chimpanzees. Another species is the nocturnal West African wood–owl (Ciccava woodfordi) (Sugiyama 1989; Carvalho et al. 2010; Hockings et al. 2012). The prey reported here was a diurnal bird species, the black–throated coucal. Fujimoto & Shimada (2008) reported three cases of bird consumption at Mahale, Tanzania, and reviewed the predation of wild birds in chimpanzees including other study sites; Bossou, Ndoki, Kibale and Gombe. The current observation is in line with these reports: The chimpanzee captured nestlings opportunistically upon detection and was solitary at the time.

After opportunistic prey–capture, chimpanzees are reported to display a variety of behaviors. At Mahale, where predation on birds is observed more frequently than at Bossou, chimpanzees show individual differences with regards to the captured birds: Some chimpanzees eat them and others not (Fujimoto & Shimada 2008). In this observation, the chimpanzee at Bossou consumed the first nestling immediately after capture, suggesting that the chimpanzee may have recognized coucals as a prey species. Unfortunately, we could not determine whether or not the second nestling was consumed.

The chimpanzee killed the second nestling more cautiously by slapping over time. Similar to the previously observed predation of birds at Mahale, chimpanzees at Bossou also sometimes discard captured animals without consumption (Ohashi 2006), and sometimes is accompanied by toying (with the prey) behavior (Hirata et al. 2001; Carvalho et al. 2010). Here, we saw the chimpanzee carrying the nestling after the slapping behavior. Hockings and others (2012) noted that accompanying behaviors, including grooming, plucking, rubbing, slapping, or carrying a captured animal, rarely occurs in adult chimpanzees at Bossou. Thus, the present observation added an interesting case of predatory and accompanying behavior by an adult female chimpanzee.

This research was financed by AS-HOPE of the Primate Research Institute of Kyoto University and a JSPS Grant–in–Aid for Scientific Research (#244525) to L. Yu and MEXT #24000001 to T. Matsuzawa. We thank the Direction Nationale de la Recherche Scientifique et Technologique (DNRST) and the Institut de Recherche Environmentale de Bossou (IREB) for the collaboration and the permission to conduct the research at Bossou. Special thanks are due to S. A. Gaspard, the general director of IREB, and G. Yamakoshi of Kyoto University. Thanks are due to the local assistants, especially H. Camara, for the identification of the bird and the plant. Thanks are also due to M. Fujisawa who guided and helped L. Yu during the stay at Bossou. We are also grateful to M. Hayashi, Y. Yamanashi, M. Tomonaga, G. Ohashi, K. Hockings, T. Humle, S. Carvalho, C. Sousa and A. MacIntosh for helpful comments and edits on this manuscript.

1. Carvalho S, Yamanashi Y, Yamakoshi G, Matsuzawa T 2010. Bird in the hand: Bossou chimpanzees (Pan troglodytes) capture West African wood–owls (Ciccaba woodfordi) but not to eat. Pan Afr News 17:6–9.
2. Fujimoto M, Shimada M 2008. Newly observed predation of wild birds by M–group chimpanzees (Pan troglodytes schweinfurthii) at Mahale, Tanzania. Pan Afr News 15:23–26.
3. Hawthorne WD, Jongkind CCH 2006. Woody Plants of Western African Forests: a Guide to the Forest Trees, Shrubs and Lianes from Senegal to Ghana. Royal Botanic Gardens, Kew.
4. Hirata S, Yamakoshi G, Fujita S, Ohashi G, Matsuzawa T 2001. Capturing and toying with hyraxes (Dendrohyrax dorsalis) by wild chimpanzees (Pan troglodytes) at Bossou, Guinea. Am J Primatol 53:93–97.
5. Hockings KJ, Humle T, Carvalho S, Matsuzawa T 2012. Chimpanzee interactions with nonhuman species in an anthropogenic habitat. Behaviour 149:299–324.
6. Matsuzawa T, Humle T, Sugiyama Y (eds.) 2011. The Chimpanzees of Bossou and Nimba. Springer, Tokyo.
7. Ohashi G 2006. Behavioral repertoire of tool use in the wild chimpanzees at Bossou. In: Cognitive Development in Chimpanzees. Matsuzawa T, Tomonaga M, Tanaka M (eds), Springer, Tokyo, pp. 439–451.
8. Serle W, Morel GJ, Hartwig W 1990. A Field Guide to the Birds of West Africa. Collins, London.
9. Sugiyama Y, Koman J 1987. A preliminary list of chimpanzees' alimentation at Bossou, Guinea. Primates 28:133–147.
10. Sugiyama Y 1989. Description of some characteristic behaviors and discussion on their propagation process among chimpanzees of Bossou, Guinea. In: Behavioral Studies of Wild Chimpanzees at Bossou, Guinea. Sugiyama Y (ed), Inuyama: Kyoto University Primate Research Institute, pp. 43–47.