The mona monkey (Cercopithecus mona) is one of the eight non-human primates protected in the Okomu National Park (ONP), a lowland rainforest in southwest Nigeria. Little is known about the various plant species they feed on and the nutritional profile of those plants. The objective of the study was to determine the plant species eaten by mona monkeys in ONP during the dry and rainy seasons, and their nutritional composition. Surveys were carried out in the national park in both dry and rainy seasons of 2011, 2012, and 2013. This included visual observations of their feeding behaviour, plants and plant parts eaten. This was corroborated with opportunistic collection of discarded portions which were also used for nutrients analyses. Nutritional analyses of the diets for crude protein, ether extracts, crude fibre, ash, and nitrogen free extracts were conducted, using standard procedures. The findings show that the diet of mona monkeys on ONP included 31 plant species in 22 families, and 56 % of the plant parts consumed were fruits. These included Gmelina arborea fruit and Jateorhiza macrantha seed which are new to literature on plants consumed by mona monkeys. Mona monkeys obtained 79 % of their diets within the Park, while 21 % were raided farm produce. The nutrient contents of the food plants were higher during dry than rainy season. Percent crude protein of 7.02 ±1.92 (n=14) was within the 6.4-8.0 % recommended by National Research Council for primates in captivity. Park managers are encouraged to take management actions to ensure that these monkeys source their entire food within the Park, to avoid human-wildlife conflict which could decimate their populations.

Keywords: Food plants, mona monkey, non-human primates, nutrient composition, Okomu National Park