Gautier-Hion, A., Quris, R. & Gautier, JP. Behav Ecol Sociobiol (1983) 12: 325. doi:10.1007/BF00302901
The analysis of ranging patterns of both mono and polyspecific troops of Cercopithecus cephus, C. pogonias, and C. nictitans has shown that association results in a change of habitat use, including a less intensive exploitation and a better selection of the areas with the richest supply of fruit species. Consequently, associated species of Cercopithecus showed a more efficient search for fruit and a more diversified diet. In contrast, no such evidence was found for insect foraging.
A clear interspecific division of roles in the patterns of waring about aerial and terrestrial predators has been demonstrated. The nictitans and pogonias species, living in the higher strata, were informed of terrestrial predators by C. cephus monkeys, which live lower. In turn, the latter benefitted from the C. pogonias male's loud calls given in the presence of aerial danger. Some evidence suggests that predation by the monkey-eagle upon C. cephus was decreased by the association.
Although both foraging efficiency and predator avoidance appeared to be improved by polyspecific association, several facts suggest that predation pressure, notably by the crowned hawk eagle, was the pime factor for the evolution of this life style.