Lecturer/PhD candidate, Garoua Wildlife College
habitat variation (forest-savanna mosaic) highly affects chimpanzee abundance in the MDNP
Cameroon is considered as one of the most diverse country in central Africa with a network of protected areas covering 20% of its national territory, within which the Mbam and Djerem National Park (MDNP). MDNP is located in the forest-savanna ecotone area in the central Cameroon between 5 ° 30 ' & 6° 13' N and 12 ° 13 ' & 13 ° 10 ' E. It covers an area of about 416,512 hectares and shelters the Nigeria-Cameroon chimpanzee (Pan troglodytes ellioti), the most endangered and poorly known of all currently recognized chimpanzee subspecies, with a total remaining population at between 3,500 and 9,000 living in forested habitat in the north of the Sanaga River in Cameroon and the eastern edge of Nigeria. MDNP has been considered as top priority zone for the conservation of this species by IUCN and given a wide range of its habitat, understanding their effect on the density of P. t. ellioti, the only species of great apes found in MDNP can infer important information about ecological adaptation and evolution. Close to 29,000 people inhabits the periphery of MDNP and depend on the park resources for their subsistence, emphasizing the need of sufficient data to model the density and occupancy of chimpanzee population in MDNP.To answer our research question, an interview of populations around MDNP and a surveys of chimpanzees base on the Standing Crop Nest Counts from line transects has been used. Cybertraker (database design) and the combine software packages R, Distance 7.0 (survey design), Quantum GIS 2.14.3 Essen and Presence has been used for data gathering and analysis. We have developed a typology of human-chimpanzee interactions (conflicts and cultural interactions), and have estimated the density of chimpanzee in their suitable habitat (feeding, nesting and degree of anthropogenic threats). We are currently testing the effect of different covariates (forest, savanna, threats) in order to provide a basis to predict the viability of chimpanzee population in the study area.
Abstract: Counting animals to estimate their population sizes is often essential for their management and conservation. Since practitioners frequently rely on indirect observations of animals, it is important to better understand the relationship between such indirect indices and animal abundance. The Formozov-Malyshev-Pereleshin (FMP) formula provides a theoretical foundation for understanding the relationship between animal track counts and the true density of species. Although this analytical method potentially has universal applicability wherever animals are readily detectable by their tracks, it has long been unique to Russia and remains widely underappreciated. In this paper, we provide a test of the FMP formula by isolating the influence of animal travel path tortuosity (i.e., convolutedness) on track counts. We employed simulations using virtual and empirical data, in addition to a field test comparing FMP estimates with independent estimates from line transect distance sampling. We verify that track counts (total intersections between animals and transects) are determined entirely by density and daily movement distances. Hence, the FMP estimator is theoretically robust against potential biases from specific shapes or patterns of animal movement paths if transects are randomly situated with respect to those movements (i.e., the transects do not influence animals' movements). However, detectability (the detection probability of individual animals) is not determined simply by daily travel distance but also by tortuosity, so ensuring that all intersections with transects are counted regardless of the number of individual animals that made them becomes critical for an accurate density estimate. Additionally, although tortuosity has no bearing on mean track encounter rates, it does affect encounter rate variance and therefore estimate precision. We discuss how these fundamental principles made explicit by the FMP formula have widespread implications for methods of assessing animal abundance that rely on indirect observations.
Pub.: 30 May '14, Pinned: 04 Dec '17
Abstract: Many individual researchers have used line transect counts to estimate forest primate abundance. They have devoted less attention to the interpretation of line transect data obtained by several observers, as is often the case in long-term monitoring programs. We present primate relative abundance data that 5 observers collected over 6 yr (not continuous) along 4 different transects each 4 km long in the Mwanihana Forest, Udzungwa Mountains National Park, Tanzania. Total distance walked during transect repetitions is ca. 700 km. The species we saw most frequently was the endemic Udzungwa red colobus Procolobus gordonorum (mean 0.59 groups/km walked), followed by the Angolan black-and-white colobus Colobus angolensis (0.43 groups/km) and Sykes’s monkey Cercopithecus mitis (0.35 groups/km). We sighted the endemic Sanje mangabey Cercocebus galeritus sanjei and the yellow baboon Papio cynocephalus infrequently, the latter being confined to the deciduous forest parts of the transects. We analyzed sighting frequency by gross habitat type, transect, season, and observer. Interobserver differences in the relative abundance of each species were moderate and the few cases of significant variations were due to discordance of only 1 observer from the others. Estimated distances of primate group sightings differ significantly among observers, thus preventing us from deriving estimates of absolute density. Frequency distributions of distance-class intervals are not significantly different among observers, which may indicate gross interobserver consistency in the width of the area sampled. We conclude that unless consistency in data collection is checked, as we did for 2 observers who collected data simultaneously, potential interobserver differences remain an underlying source of variance in the results that cannot be separated from other sources of variance.
Pub.: 21 Jul '06, Pinned: 20 Nov '17
Abstract: Habitat fragmentation is one of the principal causes of biodiversity loss and hence understanding its impacts on community assembly and disassembly is an important topic in ecology. We studied the relationships between fragmentation and community assembly processes in the land-bridge island system of Thousand Island Lake in East China. We focused on the changes in species diversity and phylogenetic diversity that occurred between life stages of woody plants growing on these islands. The observed diversities were compared with the expected diversities from random null models to characterize assembly processes. Regression tree analysis was used to illustrate the relationships between island attributes and community assembly processes. We found that different assembly processes predominate in the seedlings-to-saplings life-stage transition (SS) vs. the saplings-to-trees transition (ST). Island area was the main attribute driving the assembly process in SS. In ST, island isolation was more important. Within a fragmented landscape, the factors driving community assembly processes were found to differ between life stage transitions. Environmental filtering had a strong effect on the seedlings-to-saplings life-stage transition. Habitat isolation and dispersal limitation influenced all plant life stages, but had a weaker effect on communities than area. These findings add to our understanding of the processes driving community assembly and species coexistence in the context of pervasive and widespread habitat loss and fragmentation.
Pub.: 19 Jul '16, Pinned: 13 Jun '17
Abstract: Habitat loss and fragmentation are major threats to biodiversity, yet separating their effects is challenging. We use a multi-trophic, trait-based, and spatially explicit general ecosystem model to examine the independent and synergistic effects of these processes on ecosystem structure. We manipulated habitat by removing plant biomass in varying spatial extents, intensities, and configurations. We found that emergent synergistic interactions of loss and fragmentation are major determinants of ecosystem response, including population declines and trophic pyramid shifts. Furthermore, trait-mediated interactions, such as a disproportionate sensitivity of large-sized organisms to fragmentation, produce significant effects in shaping responses. We also show that top-down regulation mitigates the effects of land use on plant biomass loss, suggesting that models lacking these interactions—including most carbon stock models—may not adequately capture land-use change impacts. Our results have important implications for understanding ecosystem responses to environmental change, and assessing the impacts of habitat fragmentation.
Pub.: 21 Sep '16, Pinned: 13 Jun '17