Plant Foods Consumed by Pan: Exploring the Variation of Nutritional Ecology Across Africa
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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 000:000–000 (2010) Plant Foods Consumed by Pan: Exploring the Variation of Nutritional Ecology Across Africa Gottfried Hohmann,1* Kevin Potts,2 Antoine N’Guessan,1,3 Andrew Fowler,1,4 Roger Mundry,1 Joerg U. Ganzhorn,5 and Sylvia Ortmann6 1Department of Primatology, Max-Planck-Institute for Evolutionary Anthropology, D-04103 Leipzig, Germany 2Department of Anthropology, Yale University, New Haven, CT 3Swiss Centre of Scientific Research in Coˆte d’Ivoire (CSRS) and University of Cocody, 01 BP 1303, Abidjan 01, Coˆte d’Ivoire 4Department of Anthropology, University College London, London, UK 5Department of Animal Ecology and Conservation, Hamburg University, 20146 Hamburg, Germany 6Leibniz Institute for Zoo and Wildlife Research, 10315 Berlin, Germany KEY WORDS chimpanzee; bonobo; frugivory; diet quality; geographic variation ABSTRACT It has been shown that differences in nutrient components. Overall plant samples collected at resource density and nutrient supply affect variation in each site differed in terms of macronutrient content. ranging patterns, habitat use, and sociality. Among However, nutritious quality and gross energy content of nonhuman primates, chimpanzees (Pan troglodytes)and food samples were similar suggesting that dietary qual- bonobos (P. paniscus) have often been used as models ity reflects selectivity rather than habitat ecology. The for the link between social system and habitat ecology. quality of plant foods consumed by bonobos was within Field reports suggest that resource density is higher in the range of chimpanzees and the quality of plant foods habitats occupied by bonobos (compared to chimpanzee consumed by western chimpanzees was not higher than habitats), and in the West (compared to the East) of the that of eastern chimpanzees. While the results showed range of chimpanzees. In this study we compared diet significant variation across forests inhabited by Pan, quality at the level of species and populations using in- theydidnotmatchwithgeographicalpatternsbetween formation from nutritional analyses of fruit and leaves and within Pan species as proposed in previous studies. consumed by chimpanzees (three) and bonobos (one This suggests that the nutritional quality of the habitat population). Quality of plant foods was assessed on the is not always a reliable predictor of the quality of the basis of a) the concentration of macronutrients, diet. Am J Phys Anthropol 000:000–000, 2010. VC 2009 fiber, and anti-feedants, and b) associations of different Wiley-Liss, Inc. The diet of medium or small body sized vertebrates that fluctuate in time and space (Hashimoto et al., 2004; tends to include relatively large amounts of fruit and the Lehmann et al., 2007). preference for a fruit-based diet is usually related to the Information on the feeding ecology of Pan has been high content of easily digestible macronutrients, such as reported from a large number of sites across Africa, nonstructural carbohydrates and lipids, and to low levels including deciduous, woodland, and evergreen forests in of indigestible fibers and antifeedants (Milton, 1987). West, East, and Central Africa (Nishida and Uehara, Despite these nutritional advantages, frugivory tends to 1983; Newton-Fisher, 1999; Hunt and McGrew, 2002; be facultative in vertebrates, even among so-called fruit Morgan and Sanz, 2006). Corresponding information specialists, with constraints such as the spatio-temporal from bonobos comes from sites in the North (Badrian distribution of reproductive plant parts limiting the and Malenky, 1984; Kano, 1992), and South (Sabater Pi extent to which animals can subsist on an entirely fruit- and Vea, 1993; Hohmann et al., 2006) of the species’ dis- based diet (Rode and Robbins, 2000). Large body size generally permits a low-energy, low-nutrient density diet Grant sponsors: Max-Planck-Society; L.S.B. Leakey Foundation; (Clauss et al., 2008). As a consequence, large animals National Geographic Society; Volkswagen Foundation; Wenner Gren can subsist on low-quality plant foods with a high fiber Foundation; American Society of Primatologists; Swiss Centre of content and relatively low nutrient density while smaller Scientific Research; Chester Zoo Nigeria Biodiversity Programme; animals have to search for higher quality items (Dem- Dean’s travel Fund of UCL and Leventis Ltd.; Pro Natura Interna- ment and van Soest, 1985). In this regard chimpanzees tional/Lagos. (Pan troglodytes) and bonobos (P. paniscus) are excep- tional. In spite of their large body mass (Smith and *Correspondence to: Gottfried Hohmann, Department of Primatol- Jungers, 1997) they are among the most consistently fru- ogy, Max-Planck-Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103 Leipzig, Germany. E-mail: [email protected] givorous primates, in that they maintain their frugivo- rous habits even at times of low fruit availability (White Received 20 November 2008; accepted 21 July 2009 and Lanjouw, 1994; Wrangham et al., 1998). This adher- ence to frugivory requires flexibility in ranging and DOI 10.1002/ajpa.21168 grouping patterns, and the fission-fusion system of Pan Published online in Wiley InterScience is likely to be one adaptation for exploiting food patches (www.interscience.wiley.com). VC 2009 WILEY-LISS, INC. 2 G. HOHMANN ET AL. tributional range, which is entirely restricted to the ing on the abundance, distribution, and quality of avail- Democratic Republic of Congo. able plant foods, ranging from fruit to herbaceous vege- Habitats occupied by Pan differ in terms of their floris- tation (Malenky et al., 1994; Wrangham, 2000; Lambert, tic composition (Rodman, 2002) and resource abundance 2007). However, the original model that emphasized con- (Doran et al., 2002) and this variation is thought to sistent disparity between the two sister species affect habitat use, diet composition, and sociality both (Wrangham, 1986) is not unchallenged. First, although a within and between the species (Wrangham, 1986; comparison of Lomako bonobos with chimpanzees from Boesch, 1996). Comparison of hair samples from two Gombe (Tanzania) suggested that bonobos have access to populations of savanna chimpanzees revealed different larger food patches of tree fruits than chimpanzees (White isotope signatures which were related to foraging behav- & Wrangham, 1988), a comparison of Lomako bonobos ior and nutrient intake (Schoeninger et al., 1999). The with chimpanzees from Kanyawara (Uganda) did not con- two chimpanzee populations at Gombe and Mahale differ firm the proposed differences in grouping and food distri- in terms of food selection and food processing (Nishida et bution (Chapman et al., 1994). Similarly, though Malenky al., 1983) and similar differences in the use of plant (1990) proposed that the quality of fruit consumed by foods have been reported from other communities Lomako bonobos exceeds that consumed by East African (Newton-Fisher, 1999; Boesch et al., 2006). Although chimpanzees, nutritional analyses of food from a bonobo other factors are likely to be involved, ecological parame- population from Salonga and a population of Nigerian ters are thought to be the key underlying the observed chimpanzees from Gashaka (Nigeria) indicated both simi- variation. Despite the considerable attention given to the larities and differences (Hohmann et al., 2006). While influence of food distributional patterns in space and plant foods of the two species were similar in terms of time as key ecological determinants of these intra- and their overall composition, they differed in terms of how interspecific variations (Chapman et al., 1995; Doran et macronutrients and antifeedants were associated. Results al., 2002), no explanatory patterns have yet emerged. from this study indicate that it is not nutrient content but Assessments of spatial and temporal patterns of resource the association of macronutrients with antifeedants that abundance within and between sites are frequently affects fruit quality between the two species. based on rainfall data and phenological accounts such as Second, recent information from long-term chimpanzee leaf flushing and fruit production (Tutin and Fernandez, study sites has yielded a complex scenario and has 1993). While these approaches address some quantitative shifted key assumptions of previous models (Mitani et aspects of food availability, an often overlooked source of al., 2000; Lehmann and Boesch, 2004; Murray et al., variability among sites is the nutrient content and nutri- 2006). There is considerable variation in the grouping ent density of plant foods. Studies on herbivores have patterns and bonding relationships between and within shown how variation of food quality can promote or con- the sexes among populations of chimpanzees. The varia- strain activity budgets, ranging patterns and sociality, tion in chimpanzee sociality has been related to differen- such as female gregariousness, in a similar manner as ces in resource distribution (Balcomb et al., 2000; Leh- food distribution and predation pressure (Hamel and mann et al., 2007), and demography (Lehmann and Cote, 2007; Bailey and Provenza, 2008). The ideal free Boesch, 2004), leading to a proposed dichotomy between theory offers a framework that explains the relationship East and West African chimpanzees (Doran et al., 2002). between habitat quality, population density and resource While the ecological differentiation fits the original competition (Fretwell and Lucas, 1970; Fretwell, 1972). model, the geographic location