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The influence of ecological and human factors on western gorilla and central chimpanzee density and ranging patterns in a non-protected area in southeast Cameroon

Most western lowland gorilla studies have been done in reserves or relatively undisturbed areas. In most cases, the aim has been to assess the influence of ecological (e.g. fruit availability) and social (group size and composition) factors on diet and ranging patterns (especially daily path lengths – DPLs; e.g. Doran et al., 2002; Doran-Sheehy et al., 2004). For example, a common trend across sites is that in periods of fruit scarcity, gorillas eat more herbs and DPLs are shorter due to the clumped distribution of herbaceous foods; but in periods of fruit abundance, DPLs are longer because gorillas will incorporate more fruits in their diet and travel long distances to find important fruiting trees which are patchily distributed. The lack of studies on central chimpanzee ranging patterns is probably due to the fact that DPLs are difficult to measure.Studies on diet and DPLs in relatively undisturbed areas only helped to describe the NATURAL BEHAVIOUR of gorillas. Their ACTUAL BEHAVIOUR in highly disturbed areas might be different. For example, Etiendem (2013) recently showed that cross river gorillas at Mawambi Hills prefer steep ridges where food resources are scarce, but they avoid food-rich lowland forest due to intense human activity in these areas. Some other studies just assessed how habitat availability and human activity in non-protected areas influence chimpanzee and gorilla distribution (not DPLs). These were generally short-term descriptive studies (some were based on one-off survey datasets). These studies failed to incorporate long term ecological data (e.g. phenology, rainfall, temperature).The purpose of this PhD project is to explore niche differentiation of sympatric chimpanzees and gorillas under high human activity levels and climate change scenarios. Insights emerging from the study will elucidate  the impact of different levels of ecological and human factors on chimpanzee and gorilla abundance and ranging patterns in a disturbed site, and help to test the generality of the conclusions drawn from relatively undisturbed sites. For example, it is well documented that gorilla DPLs increase in periods of fruit abundance. However, the extent to which fruit availability influence gorilla DPLs WHEN POACHING is high is unknown. And despite high fruit availability, DPLs might be shorter due to high levels of human encroachment in ape habitats. Previous long-term studies in reserves did not investigate this possibility, and La Belgique site offers an excellent opportunity to study the behaviour of ape populations permanently threatened by human activities. Towards this objective, we specifically aim to:Assess resource availability to chimpanzees and gorillas in terms of habitat types, food tree and herb species, and food biomass;Evaluate the scope of human activities;Determine and rank important species and habitats used by chimpanzees and gorillas;Estimate spatial and temporal variations in chimpanzees and gorilla density Monitor the effect of important resource availability and human activities on chimpanzees and gorilla density and ranging patterns.
Datum:3 mrt 2014  →  Heden
Project type:PhD project