Barrett, Louise; (1996) Foraging strategies, range use and territoriality of grey-cheeked mangabeys in Kibale Forest, western Uganda. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This study investigates the foraging strategies and patterns of range use of two sub-populations of grey-cheeked mangabeys (Cercocebus albigena) in the Kibale Forest National Park, Uganda. Data were collected during a fourteen month field study at the Ngogo study site, located in the central block of the forest, and compared with that collected by Peter Waser at the Kanyawara field site, located 10km to the North. The results show that the Kibale mangabeys are largely frugivorous, opportunistic foragers; the fruit resources which are actively selected by the animals tend to be large, patchily distributed in space and unpredictable in their fruiting patterns. However, the diet also contained a "core" of abundant, uniformly-distributed and reliable fruit sources. A simple optimality model and stochastic dynamic programming were used to identify the factors underlying patch choice. Temporal variation in food abundance was shown to have little influence over mangabey foraging effort. However, diet selectivity increased and dietary diversity decreased when food availability was low. By contrast, spatial variation in resource availability had a very strong effect on the travel costs incurred by the mangabey group; day journey length and time spent moving significantly increased as the "patchiness" of their food resources increased. Ecological factors were shown to influence range use, but could not explain all the variation. Random walk simulations and a model of encounter rates revealed that social factors were also an important influence on the use of space. These results were combined with information on male calling behaviour in order to determine whether the same spacing system could account for the widely different spacing patterns shown by the Ngogo and Kanyawara mangabeys. Finally, the potential for, and occurrence of, territorial behaviour was compared between the two Kibale sub-populations. It was shown that while the Ngogo mangabeys were capable of territoriality and displayed evidence of a territorial strategy, the home range of the Kanyawara sub-population was uneconomic to defend. Hypotheses concerning the function of territoriality were then tested for the Ngogo sub-population, and it was concluded that the primary function was mate defence by males.

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