Possible Case of Predation on a Chimpanzee by a Leopardq_in the Petit Loango Reserve, Gabon.

There have been reports on predation on chimpanzees by large carnivores. In Mahale, at least 4 chimpanzees were eaten by lions in 1989, when lions visited and stayed in the home range of a study group (1). In a rain forest habitat, where lions are not common predators, only leopards are potential predators on chimpanzees. Although there have been reports that chimpanzees attacked or chased leopards away, and even killed the cub of a female leopard, Boesch reported several cases in which chimpanzees were attacked or killed by leopards (2, 3, 4). He supposed that predation by leopards was the first cause of mortality of chimpanzees in Tai Forest, and pointed out that the density of leopards might be a factor influencing local differences in the party size of chimpanzees.
This paper reports on possible predation on an adult male chimpanzee by a leopard in the Petit Loango Reserve. The Petit Loango Reserve, 2o17'S 9o35 E, is located on the western seashore of Gabon. A tropical rain forest ranges from 30 m from the sea line to the interior, with patchy savanna vegetation in it (5). Seven species of primates live there, including gorillas (Gorilla g. gorilla) and chimpanzees (Pan t. troglodytes), and the area also supports large mammals such as elephants, African buffaloes, leopards and antelopes (6, 7).
On August 7, 1995, I found the carcass of a chimpanzee in a forest about 300 m from the sea line. A part of the body that included the shoulders was on the ground with hairs scattered around it. The left hand was found 3 m north of the shoulder, and the lower half of the body was found 10 m north of the left hand. The right hand was found 17 m east of the shoulder, and the head was found 15 m south of the right hand, with its eyes wide opened (Fig. 1). The abdominal region and internal organs were not found, probably because they had been eaten. The head of the chimpanzee was infested with maggots, but the blood remaining on fallen leaves was not dry, indicating that the predation had occurred 1 or 2 days before.
The cranial bone was collected and examined (Fig. 2). There was no injury remaining on the skull. The canines were large. Third molars were all erupted completely, but with slight wear. Thus this chimpanzee was considered to be a late adolescent male of 12 or 13 years old (Mouri, personal communication).
Leopard dung was found at the side of the chimpanzee shoulders, and there were new footprints of an adult leopard in a savanna grassland about 20 m from the carcass. These remains suggest that an adult leopard ate a late adolescent male chimpanzee, which was probably killed by the leopard because leopards do not usually eat dead animals. Although I do not know whether this chimpanzee was in good health, this observation suggests the possibility that predation by leopards is a threat for chimpanzees in this area.

References
(1) Tsukahara T 1993. Lions eat chimpanzees: the first evidence of predation by lions on wild chimpanzees. Amer. J. Primatol. 29: 1-11
(2) Kortlandt A 1963. Bipedal armed fighting in chimpanzees. Proc. 16th Int. Cong. Zool. 3: 64.
(3) Hiraiwa-Hasegawa M, Byrne RW, Takasaki H, Byrne JME 1986. Aggression toward large carnivore by wild chimpanzees of Mahale Mountains National Park, Tanzania. Folia Primatol. 47: 8-13.
(4) Boesch C 1991. The effects of leopard predation on grouping patterns in forest chimpanzees. Behaviour 117: 220-242.
(5) Furuichi T, Inagaki H, Angoue-Ovono S 1997. Population density of chimpanzees and gorillas in the Petit Loango Reserve, Gabon: employing a new method to distinguish between nests of the two species. Int. J. Primatol. 18: 1029-1046.
(6) Wilks C 1990. La Conservation des Ecosystems Forestiers du Gabon, IUCN, Switzerland.
(7) Yamagiwa J, Angoue-Ovono S, Kasisi R 1995. Densities of ape's food trees and primates in the Petit Loango Reserve, Gabon. Afr. Study Monogr. 16: 181-193.

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