• Assessment of in situ nest decay rate for chimpanzees (Pan troglodytes ellioti Matschie, 1914) in Mbam-Djerem National Park, Cameroon: implications for long-term monitoring

      Kamgang, Serge Alexis; Carme, Tuneu Corral; Bobo, Kadiri Serge; Abwe, Ekwoge E.; Gonder, Mary Katherine; Sinsin, Brice (Springer, 2020)
      Accurate assessment of great ape populations is a prerequisite for conservation planning. Indirect survey methods using nest and dung, and a set of conversion parameters related to nest decay rates, are increasingly used. Most surveys use the standing crop nest count (SCNC) method, whereby nests are counted along transects and the estimated nest density is converted into chimpanzee density using an often non-local nest decay rate. The use of non-local decay rate is thought to introduce substantial bias to ape population estimates given that nest decay rates vary with location, season, rainfall, nest shape, and tree species used. SCNC method has previously been applied in Mbam-Djerem National Park (MDNP) in Cameroon, for chimpanzee surveys using a non-local nest decay rate. This current study aimed to measure a local nest decay rate for MDNP and implications for chimpanzee population estimates in the MDNP. The mean nest decay rate estimated using a logistic regression analysis was 127 [95% CI (100–160)] days. Moreover, the results suggested that rainfall strongly influenced the nest decay rate over the early stage of the lifetime of the nests. The study confirms that estimates of chimpanzee density and abundance using non-local decay rates should be treated with caution. Our research emphasized the importance of using local nest decay rates and other survey methods which do not depend on decay rates to obtain more accurate estimates of chimpanzee densities in order to inform conservation strategies of these great apes in MDNP.
    • Chimpanzee accumulative stone throwing

      Kühl, Hjalmar S.; Kalan, Ammie K.; Arandjelovic, Mimi; Aubert, Floris; D’Auvergne, Lucy; Goedmakers, Annemarie; Jones, Sorrel; Kehoe, Laura; Regnaut, Sebastien; Tickle, Alexander; et al. (2016)
      The study of the archaeological remains of fossil hominins must rely on reconstructions to elucidate the behaviour that may have resulted in particular stone tools and their accumulation. Comparatively, stone tool use among living primates has illuminated behaviours that are also amenable to archaeological examination, permitting direct observations of the behaviour leading to artefacts and their assemblages to be incorporated. Here, we describe newly discovered stone tool-use behaviour and stone accumulation sites in wild chimpanzees reminiscent of human cairns. In addition to data from 17 mid- to long-term chimpanzee research sites, we sampled a further 34 Pan troglodytes communities. We found four populations in West Africa where chimpanzees habitually bang and throw rocks against trees, or toss them into tree cavities, resulting in conspicuous stone accumulations at these sites. This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees. The ritualized behavioural display and collection of artefacts at particular locations observed in chimpanzee accumulative stone throwing may have implications for the inferences that can be drawn from archaeological stone assemblages and the origins of ritual sites.
    • Chimpanzee population structure in Cameroon and Nigeria is associated with habitat variation that may be lost under climate change

      Sesink Clee, Paul R.; Abwe, Ekwoge E.; Ambahe, Ruffin D.; Anthony, Nicola M.; Fotso, Roger; Locatelli, Sabrina; Maisels, Fiona; Mitchell, Matthew W.; Morgan, Bethan J.; Pokempner, Amy A.; et al. (2015)
      Background: The Nigeria-Cameroon chimpanzee (Pan troglodytes ellioti) is found in the Gulf of Guinea biodiversity hotspot located in western equatorial Africa. This subspecies is threatened by habitat fragmentation due to logging and agricultural development, hunting for the bushmeat trade, and possibly climate change. Although P. t. ellioti appears to be geographically separated from the neighboring central chimpanzee (P. t. troglodytes) by the Sanaga River, recent population genetics studies of chimpanzees from across this region suggest that additional factors may also be important in their separation. The main aims of this study were: 1) to model the distribution of suitable habitat for P. t. ellioti across Cameroon and Nigeria, and P. t. troglodytes in southern Cameroon, 2) to determine which environmental factors best predict their optimal habitats, and 3) to compare modeled niches and test for their levels of divergence from one another. A final aim of this study was to examine the ways that climate change might impact suitable chimpanzee habitat across the region under various scenarios. Results: Ecological niche models (ENMs) were created using the software package Maxent for the three populations of chimpanzees that have been inferred to exist in Cameroon and eastern Nigeria: (i) P. t. troglodytes in southern Cameroon, (ii) P. t. ellioti in northwestern Cameroon, and (iii) P. t. ellioti in central Cameroon. ENMs for each population were compared using the niche comparison test in ENMtools, which revealed complete niche divergence with very little geographic overlap of suitable habitat between populations. Conclusions: These findings suggest that a positive relationship may exist between environmental variation and the partitioning of genetic variation found in chimpanzees across this region. ENMs for each population were also projected under three different climate change scenarios for years 2020, 2050, and 2080. Suitable habitat of P. t. ellioti in northwest Cameroon / eastern Nigeria is expected to remain largely unchanged through 2080 in all considered scenarios. In contrast, P. t. ellioti in central Cameroon, which represents half of the population of this subspecies, is expected to experience drastic reductions in its ecotone habitat over the coming century.
    • Clubs des Amis des Gorilles in the Ebo forest, Cameroon

      Mfossa, Daniel; Abwe, Ekwoge E.; Morgan, Bethan J. (2018)
    • Community-led conservation action in the Ebo forest, Cameroon.

      Abwe, Ekwoge E.; Mfossa, DM; Morgan, Bethan J. (2015)
      The Ebo forest in Littoral Region, Cameroon harbours a rich biodiversity of primates, including gorillas and chimpanzees. The government of Cameroon launched the gazettement of the Ebo forest into a national park in 2006. However, the decree creating the park is still awaited and there is little or no wildlife law enforcement on the ground (Morgan et al. 2011). The proximity of Ebo to major urban centres like Douala, Edea and Yaoundé is a major incentive to the hunting and bushmeat trade, especially as growing agricultural products is not commercially viable given the poor state of the roads around the forest. The forest is thus a main source of livelihood to adjacent communities that depend on unsustainable hunting and the bushmeat trade for protein and income (Morgan 2004). In addition to running two biological research stations in the west and east of the forest, the Ebo Forest Research Project (EFRP) has been working with local communities, traditional and administrative authorities around the forest to conserve its rich biodiversity and habitats while waiting for the official protection of the forest (Abwe and Morgan 2012). This article is aimed at providing a summary of the community-led conservation initiatives by traditional authorities and communities around the Ebo forest since 2012.
    • Conserving the Ebo gorillas through community collaboration

      Mfossa, Daniel; Abwe, Ekwoge E.; Morgan, Bethan J. (2017)
    • Dietary ecology of the Nigeria–Cameroon chimpanzee (Pan troglodytes ellioti)

      Abwe, Ekwoge E.; Morgan, Bethan J.; Doudja, Roger; Kentatchime, Fabrice; Mba, Flaubert; Dadjo, Alvine; Venditti, Dana M.; Mitchell, Matthew W.; Fosso, Bernard; Mounga, Albert; et al. (2020)
      Examining the diets of primate populations inhabiting different habitat types could be useful in understanding local adaptation and divergence between these populations. In Cameroon, the Nigeria–Cameroon chimpanzee (Pan troglodytes ellioti) is subdivided into two genetically distinct populations that occupy different habitat types; one occurs in forests to the west and the other in a forest–woodland–savanna mosaic (ecotone) in the center of the country....
    • Environmental variability supports chimpanzee behavioural diversity

      Kalan, Ammie K.; Kulik, Lars; Arandjelovic, Mimi; Boesch, Christophe; Haas, Fabian; Dieguez, Paula; Barratt, Christopher D.; Abwe, Ekwoge E.; Agbor, Anthony; Angedakin, Samuel; et al. (Springer Science and Business Media LLC, 2020)
      Large brains and behavioural innovation are positively correlated, species-specific traits, associated with the behavioural flexibility animals need for adapting to seasonal and unpredictable habitats. Similar ecological challenges would have been important drivers throughout human evolution. However, studies examining the influence of environmental variability on within-species behavioural diversity are lacking despite the critical assumption that population diversification precedes genetic divergence and speciation. Here, using a dataset of 144 wild chimpanzee (Pan troglodytes) communities, we show that chimpanzees exhibit greater behavioural diversity in environments with more variability — in both recent and historical timescales. Notably, distance from Pleistocene forest refugia is associated with the presence of a larger number of behavioural traits, including both tool and non-tool use behaviours. Since more than half of the behaviours investigated are also likely to be cultural, we suggest that environmental variability was a critical evolutionary force promoting the behavioural, as well as cultural diversification of great apes.
    • First video footage of the elusive Ebo gorillas in Cameroon

      Mfossa, D.; Ndimbe, M.; Abwe, Ekwoge E.; Morgan, Bethan J. (2019)
    • Habitat differentiation among three Nigeria–Cameroon chimpanzee (Pan troglodytes ellioti) populations

      Abwe, Ekwoge E.; Morgan, Bethan J.; Tchiengue, Barthelemy; Kentatchime, Fabrice; Doudja, Roger; Ketchen, Marcel E.; Teguia, Eric; Ambahe, Ruffin; Venditti, Dana M.; Mitchell, Matthew W.; et al. (2019)
      Ecological niche models (ENMs) are often used to predict species distribution patterns from datasets that describe abiotic and biotic factors at coarse spatial scales. Ground-truthing ENMs provide important information about how these factors relate to species-specific requirements at a scale that is biologically relevant for the species. Chimpanzees are territorial and have a predominantly frugivorous diet. The spatial and temporal variation in fruit availability for different chimpanzee populations is thus crucial, but rarely depicted in ENMs. The genetic and geographic distinction within Nigeria–Cameroon chimpanzee (Pan troglodytes ellioti) populations represents a unique opportunity to understand fine scale species-relevant ecological variation in relation to ENMs. In Cameroon, P. t. ellioti is composed of two genetically distinct populations that occupy different niches: rainforests in western Cameroon and forest–woodland–savanna mosaic (ecotone) in central Cameroon. We investigated habitat variation at three representative sites using chimpanzee-relevant environmental variables, including fruit availability, to assess how these variables distinguish these niches from one another. Contrary to the assumption of most ENM studies that intact forest is essential for the survival of chimpanzees, we hypothesized that the ecotone and human-modified habitats in Cameroon have sufficient resources to sustain large chimpanzee populations. Rainfall, and the diversity, density, and size of trees were higher at the rainforest. The ecotone had a higher density of terrestrial herbs and lianas. Fruit availability was higher at Ganga (ecotone) than at Bekob and Njuma. Seasonal variation in fruit availability was highest at Ganga, and periods of fruit scarcity were longer than at the rainforest sites. Introduced and secondary forest species linked with anthropogenic modification were common at Bekob, which reduced seasonality in fruit availability. Our findings highlight the value of incorporating fine scale species-relevant ecological data to create more realistic models, which have implications for local conservation planning efforts.
    • Linking Behavioral Diversity with Genetic and Ecological Variation in the Nigeria-Cameroon Chimpanzee (Pan troglodytes ellioti)

      Abwe, Ekwoge E. (Drexel UniversityPhiladelphia, PA, 2018)
      The chimpanzees of Cameroon present a unique opportunity to investigate how ecological variation contributes to promoting intraspecific divergences in the endemic mammals of the region.... This thesis explores environmental and ecological differences between rainforest and ecotone habitats at a fine geographic scale, and compares and contrasts chimpanzee socioecology patterns between these habitats.
    • Phenotypic variability along a climatic gradient in a perennial afrotropical rainforest understorey herb

      Ley, Alexandra C.; Herzog, Patrick; Lachmuth, Susanne; Abwe, Abwe E.; Christian, Mbella F.; Sesink Clee, Paul R.; Abwe, Ekwoge E.; Morgan, Bethan J.; Gonder, Mary K. (2018)
      Plants evolved in response to climatic conditions, which shaped their geographic distribution, functional traits and genetic composition. In the face of climatic changes, plants have to react by either genetic adaptation, phenotypic plasticity or geographic range shift....
    • The population genetics of wild chimpanzees in Cameroon and Nigeria suggests a positive role for selection in the evolution of chimpanzee subspecies

      Mitchell, Matthew W.; Locatelli, Sabrina; Ghobrial, Lora; Pokempner, Amy A.; Sesink Clee, Paul R.; Abwe, Ekwoge E.; Nicholas, Aaron; Nkembi, Louis; Anthony, Nicola M.; Morgan, Bethan J.; et al. (2015)
      Chimpanzees (Pan troglodytes) can be divided into four subspecies. Substantial phylogenetic evidence suggests that these subspecies can be grouped into two distinct lineages: a western African group that includes P. t. verus and P. t. ellioti and a central/eastern African group that includes P. t. troglodytes and P. t. schweinfurthii. The geographic division of these two lineages occurs in Cameroon, where the rages of P. t. ellioti and P. t. troglodytes appear to converge at the Sanaga River. Remarkably, few population genetic studies have included wild chimpanzees from this region.