Temporal patterns of crop-raiding by primates: linking food availability in croplands and adjacent forest.
Abstract
The temporal pattern of foraging on crops (the equivalent to mast fruiting of forest trees) by redtail monkeys Cercopithecus ascanius, olive baboons Papio cynocephalus and chimpanzees Pan troglodytes was investigated using 23 months of data from 4 villages around Kibale National Park, Uganda. The 3 primates selected different crops or plant parts when crop-raiding. Baboons took root and tuber crops ignored by other primates, and fed on the greatest variety of crops. All 3 species preferred maize and/or bananas. Redtails ate only banana fruit, baboons ate banana fruit more frequently than pith, and chimpanzees raided pith and fruit in equal proportions. Each primate showed a distinct monthly pattern of crop foraging, significantly non-random for baboons and redtail monkeys, weakly for chimpanzees. Large inter-monthly variation was observed for all 3 primates, but was least pronounced in redtails. Raiding frequency on maize peaked approximately 8 weeks after the onset of rains and was strongly correlated between the 3 primate species. Abundant forest fruit did not diminish primate appetite for maize. Raiding frequency on bananas varied considerably despite continuous availability of fruit and pith. Peaks in banana consumption were unrelated to rainfall or maize raiding, but were associated instead with forest fruit shortages, specifically Mimusops bagshawei. Chimpanzees consumed banana pith more frequently when forest fruits were scarce, whereas baboons targeted more banana fruits. The use of banana pith by chimpanzees supports the suggestion that energy-rich pith is crucial to chimpanzees during fruit scarcity. It is suggested that the conservation of Mimusops bagshawei and other key forest fruit trees may lessen primate raiding intensity on perennial crops, e.g. bananas. Maize raiding was unaffected by forest fruit abundance. Such highly palatable crops are best planted >500 m from the forest edge. Planting agroforestry buffers along park edges creates an ideal habitat for crop-raiders. This management strategy is appropriate where human population density is low and crop raiding species are legal game, but when dangerous or destructive wildlife species forage amidst densely settled subsistence farmland, managers are challenged to separate forests from agriculture using non-palatable plant barriers or electric fences.