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The diets of all diurnal primates (Gorilla g. gorilla, Pan t. troglodytes, Mandrillus sphinx, Colobus satanas, Cercocebus albigena, Cercopithecus nictitans, C. pogonias, C. cephus ) in the Lopé Reserve, central Gabon, are described from qualitative and quantitative data collected over 10 years. A total of 397 foods were recorded, of which 91% were from plants. The diets of seven of the eight species were numerically dominated by fruit, the exception being Colobus satanas with a diet dominated by seeds. When proportion of feeding time was examined, fruit remained the dominant food class for six species, while Cercocebus albigena , like the black colobus, spent most time feeding on seeds. The number of foods recorded per species ranged from 46–220, but dietary breadth of the four species that have not been subjects of detailed study was certainly underestimated. Almost half of the foods (46%) were eaten by only one species, and only four (1%) were recorded for all eight species. At Lopé, fruit is scarce for 2–3 months during the annual dry season, and fruit crop failures can prolong this period of scarcity to as many as 8 months in some years. When fruit is scarce, the diets of all species changed to include more nonfruit foods, but chimpanzees and the three species of guenons maintained a fruit dominated diet. The total biomass of the Lopé primate community is 374 kg/km[sup 2] , which is low compared to other sites in tropical Africa. Within the Lopé community, biomass correlates negatively with degree of frugivory, suggesting that fruit availability may be critical, but this does not explain the low total biomass compared to other sites. Neither floristic diversity nor the composition of the primate community at Lopé can account for the low biomass. While historical events such as climate-induced changes in forest cover, disease, or impact of human activities cannot be ruled out, we conclude that the most likely explanation of low primate biomass is the occurrence of an ecological “catastrophe” in the fairly recent past from which populations have not yet recovered. We believe that the most likely scenario was climate-mediated disturbance of flowering of important fruit food species. Prolonged fruit scarcity would have caused mortalities and affected the most frugivorous species more severely. Am. J. Primatol. 42:1–24, 1997. © 1997 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The fruit of six species of Diospyros (Ebenaceae) provide food for eight species of diurnal primates in the Lopé Reserve, Gabon. Both succulent flesh and immature seeds are eaten but patterns of consumption vary among the primate species. Interactions between D. mannii, which has very large fruit (9 cm × 7 cm) and seeds (5 cm × 2 cm), and primates were observed in detail. D. mannii fruit are unusual, being covered by a dense mat of irritant hairs that are largely retained, but become looser on ripening, when fruit are abscissed. Primates do not eat immature seeds of this species but do predate on seeds of some other Diospyros species. Ripe flesh (and ripe seeds) of D. mannii are eaten by gorillas and chimpanzees but not by monkeys. Comparison of fruit characters and of feeding patterns of primates for the six Diospyros species suggests that large seeds are potentially vulnerable to high levels of predation but the presence of irritant hairs provides protection during fruit development. Abscission of ripe fruit (shown only by D. mannii) appears to afford additional protection from predation on ripe seeds by arboreal monkeys. These observations underline the complexity of plant-animal interactions in tropical forests and suggest that some fruit characters have evolved to reduce seed loss during maturation. [ABSTRACT FROM PUBLISHER]