Vol. 7 No.1 (2016) 5-9. and folivore needs longer feeding time. The risk of losing Two Newly Observed time when folivore fail to catch fish or vertebrate might Cases of Fish-eating in be serious for them. Examination of possible factors of fish-eating in non-human primates shed a light on this Anubis Baboons question. One of the factors is seasonality. Catching fish be- Akiko Matsumoto-Oda 1,*, Anthony D. Collins 2 comes easier during the dry season because temporary small pools or shallow rivers appear (Hamilton & Tilson, 1 Graduate School of Tourism Sciences, University of the Ryukyus, Okinawa 903-0213, Japan 1985; de Waal, 2001). Most of cases that non-human 2 The Jane Goodall Institute, Gombe Stream Research Centre, Kigoma P.O. primates obtained fishes were beside shallow water Box 185, Tanzania (Stewart, Gordon, Wich, Schroor, & Meijaard, 2008). *Author for correspondence ([email protected]) In rehabilitant orangutans in Central Kalimantan, 79% events (19/24) were in the wet-dry transition or in the dry Most non-human primates are omnivorous and eat season, and they obtained 21% (4/19) of fsh from shallow a wide variety of food types like as fruit, leaves, ponds and 79% (15/19) on riverbanks (Russon et al., 2014). seeds, insects, gums or a mixture of these items. In Hunting frequency becomes high when low availability spite of frequent eating of fish in human, there are of preferred foods create a need for fallback foods (e.g., few species to eat fishes in non-human primates. Teleki, 1973; Rose, 2001). Indeed, non-human primates Observations of fsh-eating in wild primates bring us eat fish when there are fewer terrestrial plants (de Waal, an important cue for the question why humans have 2001; Wrangham, Chenry, Seyfarth, & Sarmiento, 2009; evolved appetite for fish. Here we report two new Stewart, 2010). When the artificial supply of food was fsh-eating cases observed in anubis baboons (Papio decreased, male Japanese macaques in Koushima Island anubis) at the Mpala Research Centre, Kenya and began to eat dead fish (Watanabe, 1989). From data on the Gombe National Park, Tanzania. Both cases were baboons inhabiting the Okavango Delta in Botswana, it is observed in dry seasons, and two adult males and a assumed that the use of aquatic underground storage or- young female ate recently dead or dying fsh in each gans provided fallback food in early hominins (Wrangham, case. In these two cases, the opportunity of fsh-eat- 2005; Wrangham et al., 2009). In addition, early hominins ing occurred by chance and it will be diffcult for them possibly began to consume fsh as a by-product of eating to eat fshes ordinarily. aquatic plants or aquatic invertebrates (Stewart, 2010; Russon et al., 2014). Keywords Another factor is opportunity and propagation of Papio anubis, dead fsh, seasonality, opportunism, propa- fish-eating. Omnivores have contradictory behaviors for gation foods (omnivore’ dilemma): searching for new food items to vary their diet (food neophilia) (e.g., Barnett, 1958; Milton, 1993) and fearing novel items that may be poison- Introduction ous (food neophobia) (e.g., Weiskrantz & Cowey, 1963; In humans, fish accounted for 16.7% of the global pop- Visalberghi & Fragaszy, 1995). Long-term observation ulation's intake of animal protein in 2010 (FAO, 2014). is necessary to determine propagation speed and pattern Observations of fish-eating behavior in non-human pri- of consumption of a novel food within an animal group. mates are, however, reported only on 10 species (Russon, In Japanese macaques, Watanabe (1989) reported that Compost, Kuncoro, & Ferisa, 2014): Horsfeld’s (Bornean) fish-eating spread to 75% of the group members within tarsier (Tarsius bancanus), Philippine tarsier (Tarsius 7 years. Leca, Gunst, Watanabe, and Huffman (2007) syrichta), tufted capuchin (Cebus apella), Allen’s swamp reported that more males ate fsh than females, and that the monkey (Allenopithecus nigroviridis), long-tailed macaque dominant individuals spent more time feeding on fsh than (Macaca fascicularis), Japanese macaque (Macaca fusca- the subordinate ones. Moreover, fsh-eating behavior was ta), olive baboon (Papio anubis), chacma baboon (Papio well maintained in terms of matrilineage. This suggests ursinus), bonobo (Pan paniscus), and Bornean orangutan that dominance rank and matrilineage affect the diffusion (Pongo pygmaeus). It brings a question why human often of this behavior. eat fishes whereas non-human primates rarely eat. Some Here we report two new fsh-eating cases observed in non-human primates prey on other vertebrate, but they do wild anubis baboons and consider what kind of situation not rely on meat as a major diet (Chapman, Rothman, & fsh eating rise in. Baboons have the largest bodies among Lambert, 2012). In general, body size and diet are related: living primates inhabiting the transitional zone between the smallest primates < 1kg are insectivore, middle size forests and savannas, and their body size is similar to are frugivore and the largest size are folivore (Kay, 1984; that of early hominids. In the baboon genus, fish-eating Fleagle, 1999). This depends on that larger animals need has been reported in anubis and chacma baboons. Anubis more calories than small animals. Leaves are calories-less baboons at the Gombe National Park, Tanzania, were doi: 10.5178/lebs.2016.41 5 Received 28 November 2015. Accepted 27 December 2015. Published online 29 January 2016. © 2016 by Human Behavior and Evolution Society of Japan Fish-eating by anubis baboon observed eating the leftovers of dried small fish, dagaa, close to him, but did not notice the object that dried under the sun and left by fishermen (Goodall, AZT was looking at. Within 10m from AZR, an 1971; Ransom, 1981). Fish-eating was more common in adult male RED (unknown age, fifth-ranking) chacma baboons in Namibia, which ate both dead and groomed an estrous female, MKA (15-years-old). live fish (Hamilton & Tilson, 1985). The first case of 11:29 A recently dead or dying Kuhe foated in the wa- our new reports was observed at Mpala, Kenya, where a ter towards the shore. AZT stood up and watched baboon ate a fsh at a seasonal pool. The second case was the fsh (Fig. 1b). He entered the water and swam observed at Gombe where baboons ate a cichlid, Kuhe towards the fsh, and the two immature baboons (Boulengerochromis microlepis). followed him. AZT returned to the shore, holding the tail of the fish in his mouth (Fig. 1c). The Kuhe was approximately 40 cm in length. AZT, Methods standing at the shore, bit into the lower part of The Mpala Research Centre on the Laikipia Plateau, Kenya the head of the fsh (Fig. 1d). is located to the northwest of Mt. Kenya, where the study 11:30 AZT sat down and held the part of the fish that of baboons commenced in August 2011 (Matsumoto-Oda, he had bitten (Fig. 1e). He began to eat from the 2015). In September 2011, the size of AI group was at least neck of the fsh topped down (Fig. 1f). 62 individuals that included 10 adult males and estimate 21 11:31 The two immature baboons watched AZT from a adult females. distance of 1.5 m (Fig. 1g). AZT ate the fsh along The Gombe National Park, Tanzania, is located facing its back (Fig. 1h). Lake Tanganyika. Study of anubis baboons at Gombe 11:44 AZT ate the body of the fsh frst, and put the un- has been performed since 1967 (Packer, Tatar, & Collins, eaten part of the head and tail by his left foot (Fig. 1998). In the early years of research on the baboons, fsher- 1i). STI (15-years-old, sixth-ranking) approached men dried small fsh, Stolothrissa tanganicae (local name to a distance of 2 m and looked at AZT. is dagaa) of about 7cm size (Campbell, Verburg, Dixson, 11:48 MKA and RED passed nearby AZT. Moreover, & Hecky, 2008), on the beach on the shores of the lake. an estrous female AJA (13-years-old) approached Baboons were observed picking up the leftovers (Ransom, to AZT, and they left together. STI went over to 1981; Goodall, 1971). However, the catching of fish by where AZT had been sitting and ate the remain- local people was prohibited by the national park authorities der of the fsh. in 1998 (Pusey, Wilson, & Collins, 2008), and since then, 11:51 STI left. baboons have had no access to fsh made available through human activities. In September 2008, the BA group was composed of a total of 38 individuals that included 10 adult Discussion males and 13 adult females. In Case I and II, anubis baboons ate fish in early dry or dry season. According to the study by Barton and Whiten (1993) that baboon foods were more numerous in the rainy Results season than in the dry season in nearby Mpala, Case I was Case I, Mpala observed during a period of scarce food. Previous studies 13 September, 2011 (early dry season) on orangutans and Japanese macaques also reported that 06:13 The observation of the AI group was started fish-eating occurred when fruits or foods were scarce from the top of the cliff where was their sleeping (Watanabe, 1989; Russon et al., 2014). Our observation site. supports a hypothesis that fsh-eating is favored as a fall- 08:20 The group descended the cliff. The group spread back food when fruits or foods were scarce. out and some individuals stopped at a pool that The baboons seemed to fnd fsh by chance that were is naturally dammed in the dry season. The dying or had recently died and subsequently ate them in distance in a straight line from the top of the cliff both of the cases.