Tannins are known to have anti-digestive properties among primates and undoubtedly influence food selection among grey-cheeked mangabeys (Lophocebus ugandae) living in Mabira and Lwamunda forest reserves. During the 24 months study, we observed the feeding behaviour of three groups of mangabeys in forests with different levels of degradation and management histories. Results indicated that mangabeys selected fruits parts based on tannin levels. Chemical analysis indicated that fruit parts with tannin levels exceeeding 2.6g/100 catechin equivalent were invariably rejected. These were unripe fruit pulp and mature seed. Accepted parts included endosperms of immature fruit and ripe pulp belonging to 12 priority tree species. This selection criteria applied to all types of fruit regardless of forest habitat. The level of rejection of fruit parts with high levels of tannins was more frequent in the severely degraded Lwamunda forest reserve than in Mabira. Consumption of endosperms of unripe fruit appears to be related to fruit scarcity.
Key words: Tannins, food scarcity, Lake Victoria Basin forests, primates,fruit processing.