Cross River Gorilla Research Articles

Globalization, Orature and the Preservation of Animal Species: The Example of Conversation on Cross River Gorilla in Bechati Tradition

Globalization, Orature and the Preservation of Animal Species: The Example of Conversation on Cross River Gorilla in Bechati Tradition

Effects of anthropogenic activities of Okwangwo people on the survival of cross river gorilla (Gorilla gorilla diehli) in Boki L.G.A, cross river state, Nigeria

Effects of anthropogenic activities of Okwangwo people on the survival of cross river gorilla (Gorilla gorilla diehli) in Boki L.G.A, cross river state, Nigeria

Past Connectivity but Recent Inbreeding in Cross River Gorillas Determined Using Whole Genomes from Single Hairs.

The critically endangered western gorillas (Gorilla gorilla) are divided into two subspecies: the western lowland (G. g. gorilla) and the Cross River (G. g. diehli) gorilla. Given the difficulty in sampling wild great ape populations and the small estimated size of the Cross River gorilla population, only one whole genome of a Cross River gorilla has been sequenced to date, hindering the study of this subspecies at the population level. In this study, we expand the number of whole genomes available for wild western gorillas, generating 41 new genomes (25 belonging to Cross River gorillas) using single shed hairs collected from gorilla nests. By combining these genomes with publicly available wild gorilla genomes, we confirm that Cross River gorillas form three population clusters. We also found little variation in genome-wide heterozygosity among them. Our analyses reveal long runs of homozygosity (>10 Mb), indicating recent inbreeding in Cross River gorillas. This is similar to that seen in mountain gorillas but with a much more recent bottleneck. We also detect past gene flow between two Cross River sites, Afi Mountain Wildlife Sanctuary and the Mbe Mountains. Furthermore, we observe past allele sharing between Cross River gorillas and the northern western lowland gorilla sites, as well as with the eastern gorilla species. This is the first study using single shed hairs from a wild species for whole genome sequencing to date. Taken together, our results highlight the importance of implementing conservation measures to increase connectivity among Cross River gorilla sites.

Increasing signs of forest fragmentation in the Cross River National Park in Nigeria: Underlying drivers and need for sustainable responses

Protected areas are expectedly intact habitats for biodiversity and key for ecosystem conservation. However, where inadequately protected, human-induced forest fragmentation can degrade them and reduce their functioning. Therefore, monitoring forests in protected areas is essential to ascertain their protection. This paper assesses forest fragmentation in the Cross River National Park, a biodiversity hotspot in the tropical rainforest of Nigeria. Forest fragmentation was analyzed using the Driver-Pressure-State-Impact-Response framework. Fragmentation analysis of the State used class-level pattern metrics on Landsat and Sentinel images from the years 2000, 2015 and 2020. Forest fragmentation has reduced total forest area, decreased average size of forest patches, increased the number of forest patches and amount of edge. Only the isolation of forest patches has not yet reached a measurable intensity. However, spatio-temporal forest fragmentation over the years 2000, 2015 and 2020 indicates a rising trend, especially between 2015 and 2020. The Drivers, Pressures, Impacts and Responses were investigated through a systematic literature review. Many studies show that the main proximate Drivers of forest fragmentation are agricultural activities mainly by the local communities, demand for forest resources by the growing population, and by external actors through illegal logging and infrastructure building, which have increased. However, wider literature highlight issues of disproportionately blaming local resource users, and the need to examine the neglect of justice, rights and local values, and their implications for sustainable protected areas. Reported Impacts include hindered migration of the endangered Cross River gorilla and impaired ecosystem services like water cycling, carbon sequestration and disease regulation. Responses have generally excluded the local communities, have failed or are yet to become effective. There is thus a need to identify, together with the involved actors, why measures have failed and to implement more sustainable options to reduce fragmentation in the park while addressing local users’ needs.

Ecological, Historical, Economic, and Political Factors Shaping the Human–Gorilla Interface in the Mone-Oku Forest, Cameroon

Cross River gorillas are the least numerous of the African ape taxa. Since their rediscovery, several organisations have sought to conserve these critically endangered apes, resulting in a “crisis conservation narrative” focused on the threats posed by local human activities. However, landscapes are not just ecological, they are also social, shaped by political and economic processes. This study examines the interconnections between humans and gorillas by approaching the Mone-Oku forest as a combination of ecological, social, and political systems. Through a combined use of botanical surveys, analyses of nesting sites, participant observation, and semistructured interviews, we obtained nuanced ecological and ethnographic insights into the human–gorilla interface. The results illustrate a history of alterations within the Mone-Oku forest, some of which are human-induced. These alterations have had both positive and negative outcomes for the gorillas and continue to the present day, where political history has shaped limited livelihood alternatives, increasing the reliance on a forest that has remained a constant in the more recent history of “developmental” neglect and isolation. However, this situation is not static, with future alterations to the forest also subject to regional and international political and economic influences, such as the increased worldwide demand for cacao.

Competition, seed dispersal and hunting: what drives germination and seedling survival in an Afrotropical forest?

Disentangling the contributions of different processes that influence plant recruitment, such as competition and seed dispersal, is important given the increased human-mediated changes in tropical forest ecosystems. Previous studies have shown that seedling communities in an Afrotropical rainforest in southeastern Nigeria are strongly affected by the loss of important seed-dispersing primates, including Cross River gorillas (Gorilla gorilla diehli), chimpanzee (Pan troglodytes elioti) and drill (Mandrillus leucophaeus). Here we study how germination and survival of tree seedlings are affected by competition and reduced seed dispersal in three contiguous forest reserves, in southeastern Nigeria, with similar mature tree species composition and structure. We use an experimental design aimed at manipulating the effect of competition among seedlings in three protected and three hunted sites within the reserves. We use a total of sixty 5 × 5 m plots of three types: plots cleared of all seedlings, plots selectively cleared of all primate-dispersed seedlings and control plots. All seedlings were identified, measured, assigned to dispersal mode and tagged, and after 1 year we evaluated survival, mortality and new recruits. We found that in hunted sites germination of abiotically dispersed species was over four times higher in cleared plots compared to control plots, whereas germination of primate-dispersed species was the same, which indicated that dispersal limitation was the dominant force in seedling recruitment in hunted sites. This was supported by the fact that the germination of all dispersal modes in the selectively cleared plots in protected sites was similar to the control plots in the same sites, but germination of abiotically dispersed species was significantly lower than in cleared plots in hunted sites. Competition among seedlings was mostly evident from the fact that 75 % more seedlings of primate-dispersed species germinated in cleared compared to control plots in protected sites. We conclude that inter-seedling competition may be irrelevant to seedling recruitment in hunted sites, where dispersal limitation appears to be a much stronger force shaping the seedling plant community, and thus hunting indirectly reverses the importance of competition and dispersal limitation in structuring seedling communities.

An Analysis of Insectivory in Cross River Gorillas (Gorilla gorilla diehli) in the Tofala Hill Wildlife Sanctuary, Cameroon

Gorillas have a wide range of food items in their diet; fruits, leaves, shoot, roots, piths, and insects hence are considered as generalists (Caldecott & Ferris, 2005; Inskipp, 2005). There exists some wide dietary flexibility between gorilla species (western and eastern gorillas). The main focus of the study was investigating on Cross River gorilla (CRG) insectivory and its influence on habitat range suitability at the Tofala Hill Wildlife Sanctuary (THWS). This was based on the hypothesis that insectivory is a determinant to habitat suitability in Cross River gorillas. Reconnaissance survey conducted resulted to 115 gorilla signs recorded amongst which were 19 gorilla dung samples. CRG habitat was characterized by indirect signs recorded within various vegetation type, canopy cover, slope and elevation. This was in order to understand and relate habitat range and food availability. Insect food availability was assessed based on the number of insect/ant mount recorded along CRG trails. Data analysis included Kolmogorov sminorv normality test and non-parametric Spearman’s Rho correlation test to measure relationships between variables and Kruskal-Wallis test to compare groups for significant difference. Cross tabulations were accompanied with Cramers’ V-test in order to measure the level of association between 2 categorical variables most especially in cases where they were nominal. Statistical observations were discussed at the 95% Confidence Level (Alpha=0.05). Fecal analysis revealed insect foods amongst fruits (Afromomum sp., Musa sp., Marantacae sp. etc.), and leaves in THWS CRG. Results showed that insect consumption seemed to decrease with increased altitude. The weak and negative relation in number of insect parts and altitude range permits that the hypothesis of this study be accepted. Concurrently, abundance of insect parts in feces was not necessarily dependent on altitude but dependent on age, hence adopting the hypothesis that insectivory is a determinant to habitat suitability in Cross River gorillas. This study is the very first confirmation that CRGs feed on insects; Dorylus ant and Macrotermes sp. and Cubitermes sp.

Folk Filmmaking: A Participatory Method for Engaging Indigenous Ethics and Improving Understanding

On an assignment to produce videos promoting Cross River gorilla conservation to indigenous communities in Nigeria and Cameroon, I invited community members to join me. I followed decolonising and feminist methodologies to develop a form of participatory video production, 'Folk Filmmaking', in which participants present their own accounts of wildlife, conservation, and environmental values by performing stories. Through the films, participants shared their knowledge as morality tales, providing contextual nuance to moral challenges, clarity on local concerns, and opportunities for better understanding of local conflicts with conservation. Most films use gorillas as a plot device but orient the moral issues not to the ape's plight but to communal struggles with challenges such as marginalisation, modernity, and corruption. The films do not say how best to conserve the last 300 Cross River gorillas but they help articulate indigenous values and show the challenges conservation must overcome. This paper shares an account of lessons learned during the project through continual, critical reflection on my process. It describes my methodology and the films produced then offers an analysis and evaluation of the project. It concludes with notes on the potential and pitfalls of participatory video in contexts of cross-cultural conflict over conservation.

Assessing the impact of seasonality on Cross River Gorilla Nest Construction at Kagwene Gorilla Sanctuary, North-West Cameroon

The Cross River gorilla, one of the most endangered subspecies of western gorilla (Gorilla gorilla) is endemic to 12 to 14 sites at the Cameroon-Nigeria border, where it is facing enormous threats from habitat loss, bush meat trade and minor climate changes (seasonal changes). In a strive to reduce the enormous stressors on this subspecies, this study assesses the impact of seasonality on nest construction by Cross River gorillas in the Kagwene Gorilla Sanctuary with the objective of evaluating the impact of seasonal changes on the nest construction. To achieve this goal, the study employed a hunter guided survey team, as well as guides/trackers of the Wildlife Conservation Society. This team regularly tracks and searches the forest for gorilla signs using vegetation trails, food prints, dung, and feeding signs which are subsequently followed onwards to the nesting site. Data were collected from January to December 2014. A total of 268 fresh gorilla nest sites were observed containing 1813 individual nests. Out of the 1813 nests recorded, 39.6% (N=718) of the nests were on the ground and 60.4% (N=1095) on trees. The frequency of each nest type varied significantly among months (P =0.4433). There was a significant effect of season on nest category. Ground categories (bare earth, herbaceous, woody and mixed) were more common in the dry season (74.9%) than in the wet season (25.1%). On the other hand, tree nests were more common in the wet season (77.4%) than in the dry season (22.6%). Mean nest diameter for the two seasons (dry and wet) was 1.1 and 1.3 m, respectively. The mean nest height was 12.5 m for both seasons. Cross River gorillas showed higher preferences for tree nests within the height class interval of 11 to 15 m (49.6%). The distribution of nests across gradient of altitudes did not vary significantly between seasons (P>0.05), and nests were most common on steep slopes (n=810). Seasonality did not significantly affect the choice of slope (P>0.05). There was a significant difference in the habitat types (primary forest, light gap, secondary forest and rock) used for nesting, with primary forest being most preferred. Nest site distribution was predominant in the northern section of the sanctuary. This study reveals that, both temperature and rainfall play an important role in nest construction by Cross River gorilla at Kagwene. Key words: Cross River gorilla, nest, seasonality, Kagwene Gorilla Sanctuary.

The Gorilla Nesting Ecology of Kagwene Gorilla Sanctuary, North West Region, Cameroon

Kagwene Gorilla Sanctuary provides a habitat for Gorilla gorilla diehli, one of the worlds’ most critically endangered sub-species. The objective of this study was to explore some important areas of the nesting ecology of Gorillas such as vegetation structure and architectural characteristics. This survey was accomplished by laying 68 circular plots of 35 m radius each, with an interval distance of 50m for elevations between 1500 m – 2038m on a line transect. A track- based search of foraging paths and knuckle-prints for fresh nest sites. Data was also recorded on the diameter at breast height of the nesting trees about 1.3 m above the ground. Moreso, the tree branches used for nesting were cut and analysed for fibre density. For the nests constructed on the ground, thickness at different elevations was recorded. The recorded data on chect-sheets was analysed by correlation and regression statistical models. For results, five habitat types were established within which a total of 525 nests (339 Tree and 186 ground) were found, 44.2 % of which were in primary forests. The result of the study recorded a significant positive correlation relationship between Tree diameter at breast height (DBH) and nest height (r = 0.331, p=0.00). Also, a weak significant relationship was observed between nest-thickness and elevation (r = 0.028, p=0.875). The plants species from eight families (Guttiferae, Meliaceae, Acanthaceae, Zingiberaceae, Caesalpinioideae, Rubiaceae, Meliaceae, and Commelinaceae) occurred in more than one elevation accounting for abundant nesting materials. 86.4% of nesting trees had fibre density between 0.6 – 1.0, with mean fibre density = 0.82, which is indicative of hard wood. Finally, this study has revealed that some ecological features like habitat structure, vegetation type, DBH, and elevation gradients have impact on the Gorilla nest-construction behavior. However, further studies should be carried out on tree crown effect on nesting, the nutritional constituents of nesting material and the behavioural ecology of gorillas.

Geographic variation in gorilla limb bones

Gorilla systematics has received increased attention over recent decades from primatologists, conservationists, and paleontologists. Studies of geographic variation in DNA, skulls, and teeth have led to new taxonomic proposals, such as recognition of two gorilla species, Gorilla gorilla (western gorilla) and Gorilla beringei (eastern gorilla). Postcranial differences between mountain gorillas (G. beringei beringei) and western lowland gorillas (G. g. gorilla) have a long history of study, but differences between the limb bones of the eastern and western species have not yet been examined with an emphasis on geographic variation within each species. In addition, proposals for recognition of the Cross River gorilla as Gorilla gorilla diehli and gorillas from Tshiaberimu and Kahuzi as G. b. rex-pymaeorum have not been evaluated in the context of geographic variation in the forelimb and hindlimb skeletons.Forty-three linear measurements were collected from limb bones of 266 adult gorillas representing populations of G. b. beringei, Gorilla beringei graueri, G. g. gorilla, and G. g. diehli in order to investigate geographic diversity. Skeletal elements included the humerus, radius, third metacarpal, third proximal hand phalanx, femur, tibia, calcaneus, first metatarsal, third metatarsal, and third proximal foot phalanx. Comparisons of means and principal components analyses clearly differentiate eastern and western gorillas, indicating that eastern gorillas have absolutely and relatively smaller hands and feet, among other differences. Gorilla subspecies and populations cluster consistently by species, although G. g. diehli may be similar to the eastern gorillas in having small hands and feet. The subspecies of G. beringei are distinguished less strongly and by different variables than the two gorilla species. Populations of G. b. graueri are variable, and Kahuzi and Tshiaberimu specimens do not cluster together. Results support the possible influence of higher-altitude Pleistocene refugia on patterns of geographic variation in gorillas.

Evaluating the potential effectiveness of alternative management scenarios in ape habitat

SUMMARYChoosing appropriate management strategies and effective conservation actions requires information about the future consequences of current conservation actions; however, this crucial information is rarely available to conservation planners. This study applies scenario planning and agent-based modelling (ABM) to assess the potential impact of alternative management strategies on future suitability and functional connectivity of Cross River gorilla (CRG) habitat in the Nigeria–Cameroon border region. The CRG population is small and fragmented, with many subpopulations and migration corridors located outside protected areas. This study used ABM to simulate human land use in the study area over a period of 15 years under different management scenarios and assessed the impact on future suitability and functional connectivity of CRG habitat. The simulations showed that a landscape approach with greater focus on interventions to change human behaviour towards conserving gorillas and sustainable forest use would result in greater improvement in habitat suitability and functional connectivity compared to focusing on improving law enforcement within existing protected areas. However, the best scenarios were when both law enforcement and behaviour change increased. The results highlight the importance of human behaviour change to conservation in human-dominated landscapes and can inform conservation planning and management of other species and in similar landscapes.

The geographic distribution of genetic diversity within gorillas.

Gorillas, like all non-human great apes, are endangered. Understanding the distribution of genetic diversity across their range is important because low diversity may arise in small populations through increased inbreeding, and, by reducing reproductive fitness, may lead to decreased chances of persistence of a given population. Previous studies found higher genetic diversity in the western (Gorilla gorilla) than in the eastern gorillas (Gorilla beringei), but rarely employed individuals of known geographic origin to investigate the distribution of diversity across multiple populations. The present study fills that gap by analyzing 1,161 individuals from nine sites across all four currently recognized Gorilla subspecies. Genetic diversity at each site was estimated using published data from seven highly-variable microsatellite loci. We found that the small and fragmented populations of Cross River gorillas, eastern lowland gorillas and mountain gorillas were less diverse than any of the five analyzed western lowland gorilla populations. The higher levels of genetic variation within the western lowland gorillas might be best explained by the facts that they (i) exhibit larger present and past effective population sizes than the other subspecies and (ii) maintain higher rates of gene flow through the existence of largely continuous habitat within their range. With regard to conservation, the high genetic diversity within western lowland gorillas is encouraging and retention of dispersal corridors between already protected areas is essential. Am. J. Primatol. 77:974-985, 2015. © 2015 Wiley Periodicals, Inc.

Detection dog efficacy for collecting faecal samples from the critically endangered Cross River gorilla (Gorilla gorilla diehli) for genetic censusing.

Population estimates using genetic capture–recapture methods from non-invasively collected wildlife samples are more accurate and precise than those obtained from traditional methods when detection and resampling rates are high. Recently, detection dogs have been increasingly used to find elusive species and their by-products. Here we compared the effectiveness of dog- and human-directed searches for Cross River gorilla (Gorilla gorilla diehli) faeces at two sites. The critically endangered Cross River gorilla inhabits a region of high biodiversity and endemism on the border between Nigeria and Cameroon. The rugged highland terrain and their cryptic behaviour make them difficult to study and a precise population size for the subspecies is still lacking. Dog-directed surveys located more fresh faeces with less bias than human-directed survey teams. This produced a more reliable population estimate, although of modest precision given the small scale of this pilot study. Unfortunately, the considerable costs associated with use of the United States-based detection dog teams make the use of these teams financially unfeasible for a larger, more comprehensive survey. To realize the full potential of dog-directed surveys and increase cost-effectiveness, we recommend basing dog-detection teams in the countries where they will operate and expanding the targets the dogs are trained to detect.

Inference of gorilla demographic and selective history from whole-genome sequence data.

Although population-level genomic sequence data have been gathered extensively for humans, similar data from our closest living relatives are just beginning to emerge. Examination of genomic variation within great apes offers many opportunities to increase our understanding of the forces that have differentially shaped the evolutionary history of hominid taxa. Here, we expand upon the work of the Great Ape Genome Project by analyzing medium to high coverage whole-genome sequences from 14 western lowland gorillas (Gorilla gorilla gorilla), 2 eastern lowland gorillas (G. beringei graueri), and a single Cross River individual (G. gorilla diehli). We infer that the ancestors of western and eastern lowland gorillas diverged from a common ancestor approximately 261 ka, and that the ancestors of the Cross River population diverged from the western lowland gorilla lineage approximately 68 ka. Using a diffusion approximation approach to model the genome-wide site frequency spectrum, we infer a history of western lowland gorillas that includes an ancestral population expansion of 1.4-fold around 970 ka and a recent 5.6-fold contraction in population size 23 ka. The latter may correspond to a major reduction in African equatorial forests around the Last Glacial Maximum. We also analyze patterns of variation among western lowland gorillas to identify several genomic regions with strong signatures of recent selective sweeps. We find that processes related to taste, pancreatic and saliva secretion, sodium ion transmembrane transport, and cardiac muscle function are overrepresented in genomic regions predicted to have experienced recent positive selection.

Habitat Suitability Modeling of Endangered Primates in Nigeria: Integrating Satellite Remote Sensing and Spatial Modeling Techniques

This paper investigates the impacts of forest cover and spatial structure changes on the forest landscape across Afi-Mbe-Okwangwo protected area of Cross River State, Nigeria and its corresponding implication on two endangered primates (Cross River Gorilla and Nigeria-Cameroon Chimpanzee) habitat using satellite remote sensing and modeling techniques. Using remote sensing change detection analysis, the spatial extent and annual rate of deforestation for the study area was determined as 34,620 hectares and 1.5% respectively (from 2000 to 2014). The protected areas with highest annual deforestation rates were Afi Mountain Wildlife Sanctuary (2.6%) and Mbe Mountains (2.2%), both prominent for gorilla and chimpanzee sightings and nests. Further investigations on changes to the forest landscape structure revealed high levels of forest fragmentation across the study area for the 14-year period investigated. As a means of further understanding effects of forest landscapes changes across the study area, a 14-year forward simulation was performed using the Markov model as to determine the spatial extent of futuristic forest cover changes. The results showed that if this current trend of forest cover change continued, 28,121 hectares of forests would be lost to deforestation in 2028 (approximately 16% of the total landmass of the entire study area). Using Maxent modeling, suitable primate habitats were predicted and the total coverage determined as 30,940 hectares (54.4% situated in CRNP—Okwangwo division, 29.4% in AMWS, 14.3% in Mbe Mountains and 1.9% in ARFR). Further analysis revealed 6468 hectares of predicted primate habitat were affected by deforestation in 2014 (21% of the predicted primate habitats). These results indicate that suitable primate habitats (particularly for gorillas and chimpanzees) are under immense pressure from deforestation and forest fragmentation. This paper presents a cost effective and time saving approach for determining suitable primate habitats and understanding the effects of forest transition on primate habitat suitability.

Dynamics of Forest Landscape Transition across Protected Areas in the Niger Delta from 1986 to 2014

The overall aim of this study was to conduct a spatially explicit study of forest cover changes across 13 selected protected areas (PAs) across the study area using a combination of satellite remote sensing and ground data. The objectives of the study included: determine the spatial extent of forest landscape for selected PAs using three epochs of satellite imagery (1986, 2000 and 2014); determine the spatial extent and rates of forest transition over two 14-year periods (1986 to 2000 and 2000 to 2014); and provide a comprehensive summary of current forest landscape status in the study area. The results indicated that the spatial extent of forest landscape for the 13 FRs was 522,164, 481,870 and 457,651 hectares in 1986, 2000 and 2014 respectively. The forest cover transition for the two 14-year periods investigation showed a larger percentage of forest landscape across the 13 FRs were more affected by deforestation in comparison to afforestation. The overall annual deforestation rates for the PAs were 0.82% and 0.68% for 1986 to 2000 and 2000 to 2014 time periods. The annual afforestation rates for both 14-year periods were 0.38% and 0.39% respectively. Based on the results being obtained there was an urgent need to review the ways forest reserves and national parks in Cross River state were managed. The promotion of forest conservation was vital to the preservation of existing forest landscapes and endangered wildlife, such as the Cross River Gorilla gorilla and Nigeria-Cameroon chimpanzees. The role of community participation with the assistance of government and conservation organizations would prove effective in forest monitoring activities across the state. In conclusion, results of this study showed the potential of incorporating satellite remote sensing and ground truth data for better understanding the spatial dynamics of forest cover in PAs across the Niger Delta region.

Informing conservation management about structural versus functional connectivity: A case‐study of Cross River gorillas

Connectivity among subpopulations is vital for the persistence of small and fragmented populations. For management interventions to be effective conservation planners have to make the critical distinction between structural connectivity (based on landscape structure) and functional connectivity (which considers both landscape structure and organism-specific behavioral attributes) which can differ considerably within a given context. We assessed spatial and temporal changes in structural and functional connectivity of the Cross River gorilla Gorilla gorilla diehli (CRG) population in a 12,000 km(2) landscape in the Nigeria-Cameroon border region over a 23-year period, comparing two periods: 1987-2000 and 2000-2010. Despite substantial forest connections between occupied areas, genetic evidence shows that only limited dispersal occurs among CRG subpopulations. We used remotely sensed land-cover data and simulated human pressure (using a spatially explicit agent-based model) to assess human impact on connectivity of the CRG population. We calculated cost-weighted distances between areas occupied by gorillas as measures of connectivity (structural based on land-cover only, functional based on both land-cover and simulated human pressure). Whereas structural connectivity decreased by 5% over the 23-year period, functional connectivity decreased by 11%, with both decreasing more during the latter compared to the earlier period. Our results highlight the increasing threat of isolation of CRG subpopulations due to human disturbance, and provide insight into how increasing human influence may lead to functional isolation of wildlife populations despite habitat continuity, a pressing and common issue in tropical Africa often not accounted for when deciding management interventions. In addition to quantifying threats to connectivity, our study provides crucial evidence for management authorities to identify actions that are more likely to be effective for conservation of species in human-dominated landscapes. Our approach can be easily applied to other species, regions, and scales.

Habitat utilization and conservation of the Cross River gorilla (<i>Gorilla gorilla diehli</i.) in Afi Mountain Wildlife Sanctuary of Cross River State, Nigeria

The Cross River gorilla is one of Africa’s most critically endangered species of primates. There is scanty information on the conservation status of this population of gorillas. This work was undertaken to ascertain the seasonal migration pattern, the feeding habits and the population status of this species of gorilla with a view to recommending the best strategies for their conservation. Two patrol teams each consisting of twelve (12) rangers were used in the study. Six sample plots (240×5 km each, totaling 7.2 km2) were selected and used simultaneously in the northern and southern parts of the sanctuary in the rainy season and repeated in the dry season in 2006 and 2007. Data collected included the number of sites of gorilla nests, number of nests per site and plant species utilized for food by the gorillas. Student’s t-test and x2 test were used to analyse data. Results indicated that the total number of nests and therefore the population of gorillas decreased significantly (p < 0.05) from 616 ±138 in 2006 to 405 ±131 in 2007 while the mean number of gorilla nests per site also decreased significantly (p < 0.05) from 10.14 ± 2.6 in 2006 to 6.6 ± 2.14 in 2007 There was no significant reduction (p > 0.05) in poaching activities and the number of poachers apprehended during the study period. Thirteen poachers were apprehended in 2006 as against 12 in 2007. The gorillas migrated to the northern part of the sanctuary in the dry season and moved to the south in the rainy season. A total of 32 plant species were found to have been utilized by the gorillas for food. The gorillas were found to be frugivorous but resorted to herbaceous plants when fruits were scarce. It was recommended that consultations be held with the members of the surrounding villages to dissuade them from gorilla hunting and habitat destruction.Keywords: Habitat utilization, conservation, Cross River gorilla, Afi Mountain, Nigeria.

Distinguishing ecological constraints from human activity in species range fragmentation: the case of Cross River gorillas

The geographic range of many species has been reduced and fragmented by human impact, and ever more species live in human-dominated landscapes where they are confined to small and often suboptimal refuge areas. A detailed understanding of the causation of species' persistence and disappearance is crucial to inform management of which interventions are likely to be most effective. Yet this information is often not available to decision makers and may, in the worst case, lead to erroneous management decisions. To clarify whether Cross River gorilla Gorilla gorilla diehli (CRG) occurrence is restricted due to ecological constraints or human disturbance, we collected extensive field data on food availability, habitat structure, human activity and wildlife abundance, which we related to CRG occurrence. We also related spatial variation in hunting pressure to human density, household forest use and topography. Our results clearly show that CRG are currently confined to refuge areas because of ongoing detrimental human activities and not because of lack of food resources. Current hunting pressure is driven by human population pressure, accessibility and socioeconomic conditions influencing household dependence on forest. A substantial amount of ecologically suitable but currently unoccupied habitat could potentially carry a much larger CRG population. Conservation management should therefore focus on reducing hunting and disturbance of CRG. In contrast, ecological restoration would not improve CRG living conditions. Our field and analytical approach is widely applicable to the rapidly increasing number of species inhabiting heavily human-influenced landscapes for identifying appropriate management interventions for their protection.