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Eco-ethological response of great apes and other rain forest mammals to selective logging in Cameroon

Project: ???project.projecttypes.project.description???PhD-project

With more than 70% of the forest surface of Cameroon allocated to logging, the survival of many rain forest species depends on the way in which timber production forests will be managed for the next decades. Management decisions should be directed towards a minimisation of the negative impacts on the ecosystem as a whole, including on the animal populations living in these forests. This requires a detailed understanding of the responses of wildlife to selective logging as it is currently practised in Central Africa. This study reports on the results of longitudinal monitoring of abundances of nine mammal species in a forest concession over a four-year period, encompassing four wildlife censuses in a 176 sq-km study area, including logged and unlogged areas. Particular attention was paid to western lowland gorillas (Gorilla gorilla gorilla) and common chimpanzees (Pan troglodytes). We studied how logging at industrial scale affects the spatial distribution of nine mammal species, including great apes, and the nature of pressures exerted on animal populations within an active forest concession in Southeast Cameroon. Our results indicate that the extraction of timber generates a spatial reorganisation of gorillas and chimpanzees, inducing local modifications to population densities. This reorganisation seems to be mainly due to human activities rather than to modifications of the habitat structure or changes in the availability of fruits. Compared to other mammals, great apes are at the two extremes of a gradient of sensitivity to the habitat disturbances created by logging. Gorillas, as well as other generalist species like duikers, seem to thrive in logged forests, probably attracted to these areas by the secondarisation of the vegetation. Their densities decrease temporarily in logging compartments during logging operations but they recover quickly, suggesting a repulsive effect of the human presence in the forest rather than a major alteration of the habitat quality for them. More specialist species like sitatungas (Tragelpahus spekei) and bushpigs (Potamochoerus porcus) seem to react by increasing the size of their foraging area. Two species identified as being explicitly vulnerable to logging activities were chimpanzees and forest elephants (Loxodonta africana cyclotis). Their abundances did not recover to the original values during the 4-year study period, indicating that they still undergo some kind of pressure after the end of logging operations. Ecological Niche Factor Analysis models showed that chimpanzee and elephant distribution is greatly affected by anthropogenic variables. Gorillas also avoid areas with high rates of human frequentation, but they are attracted to logged areas. As for the chimpanzees, their spatial distribution is influenced mainly by the presence of roads which they largely avoid. The periphery of logged areas seems to be a zone of convergence for chimpanzee communities that have probably been driven out from logging compartments during operations, but these movements of populations would be limited to short distances. The vulnerability of the chimpanzees is consequently explained by the absence of demographic mechanisms enabling them to avoid disturbed zones while reducing territorial conflicts. Knowing this, it is imperative to set up concrete conservation actions aimed at maintaining the chimpanzee populations of in Cameroonian timber production forests. Practically, selective logging would easily be compatible with the preservation of the majority of rain forest mammals if concrete measures aimed at decreasing the negative impacts of logging were effectively applied. As a general rule, the proximity between logged areas and some zones that can serve as refuge seems to be a determining factor of the persistence of rain forest mammals in logged forests. A line of thought would be thus to ensure safe shifts of populations towards these zones in order to guarantee the avoidance of disturbances and, later, the recovery of densities in logged forests. In this sense, our main recommendation consists in promoting a delimitation of logging compartments into narrow strips so as to reduce the distance to be walked by an animal to geographically avoid human disturbances. Additionally, it is necessary to set up well-designed biomonitoring programmes to follow up trends in wildlife abundances and promote a flexible management that can be adapted according to the evidence of detrimental events to wildlife. Arnhem E., Dupain J., Vercauteren Drubbel R., Devos C., Vercauteren M, (2008) Selective logging, habitat quality and home range use by sympatric gorillas and chimpanzees: a case study from an active logging concession in Southeast Cameroon. Folia primatologica 79: 1-1 Supervision Prof Dr L Van Elsacker (KMDA) | Dr M Vercauteren (Université Libre de Bruxelles | BE) | J Dupain (African Wildlife Foundation | DRC) Funding: Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture - Bourse de doctorat. | Fondation Léopold III pour l'Exploration et la Conservation de la Nature | Fonds pour Favoriser les Recherches Scientifiques en Afrique | Fondation Léon & Henri Frédéricq; Académie Royale de Belgique | F.N.R.S. - Bourse pour brefs séjours à l'étranger. Fondation David & Alice Van Buuren. Timeline: 2003 – 2008


Research outputs

Log in to Pure