Distribution, Abundance, and Biomass Estimates for Primates within Kahuzi-Biega Lowlands and Adjacent Forest in Eastern DRC

Africa’s tropical forests have been subjected to alarming rates of forest clearing in the last two decades. Baseline data are critical to understanding the impacts of large-scale habitat loss and fragmentation. This report describes the distribution and relative abundance of anthropoid primates in 1994–95 within and adjacent to Kahuzi-Biega National Park lowland sector, eastern Democratic Republic of Congo. This is a region for which few empirical data exists. Density and biomass estimates derived from transect sampling are discussed for both adjacent settlement and remote sampling zones where minimum biomass estimates are 436 kg/km2 and 663 kg/km2, respectively. With the exception of red colobus Procolobus badius in sampling zone KB 4, hunting pressures do not appear to have been excessive. The owl-faced guenon Cercopithecus hamlyni is widely distributed and relatively abundant throughout the survey areas

Forest Elephant Crisis in the Congo Basin

Debate over repealing the ivory trade ban dominates conferences of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Resolving this controversy requires accurate estimates of elephant population trends and rates of illegal killing. Most African savannah elephant populations are well known; however, the status of forest elephants, perhaps a distinct species, in the vast Congo Basin is unclear. We assessed population status and incidence of poaching from line-transect and reconnaissance surveys conducted on foot in sites throughout the Congo Basin. Results indicate that the abundance and range of forest elephants are threatened from poaching that is most intense close to roads. The probability of elephant presence increased with distance to roads, whereas that of human signs declined. At all distances from roads, the probability of elephant occurrence was always higher inside, compared to outside, protected areas, whereas that of humans was always lower. Inside protected areas, forest elephant density was correlated with the size of remote forest core, but not with size of protected area. Forest elephants must be prioritised in elephant management planning at the continental scale

A survey of elephants (Loxodonta africana) in the Kahuzi-Biega National Park lowland sector and adjacent forest in eastern Zaire

There has been considerable uncertainty about the abundance estimation of Loxodonta africana within tropical lowland moist forests in Zaire. We surveyed a 15,570 km2 area within the forests of eastern Zaire using transect sampling methods and estimated the elephant population to be 3720 (range 2300–5000) individuals. Dung pile densities were significantly different between adjacent settlement, deep forest, and deep forest core strata, with the most remote area harbouring the highest density. Evidence of elephant poaching was encountered throughout the survey area suggesting that elephant populations continue to be at severe risk

Survey of Grauer's gorillas (Gorilla gorilla graueri) and eastern chimpanzees (Pan troglodytes schweinfurthi) in the Kahuzi-Biega National Park lowland sector and adjacent forest in eastern Democratic Republic of Congo

We describe the distribution and estimate densities of Grauer's gorillas (Gorilla gorilla graueri) and eastern chimpanzees (Pan troglodytes schweinfurthi) in a 12,770-km2 area of lowland forest between the Lowa, Luka, Lugulu, and Oku rivers in eastern Democratic Republic of Congo, the site of the largest continuous population of Grauer's gorillas. The survey included a total of 480 km of transects completed within seven sampling zones in the Kahuzi-Biega National Park lowland sector and adjacent Kasese region and approximately 1100 km of footpath and forest reconnaissance. We estimate total populations of 7670 (4180-10,830) weaned gorillas within the Kahuzi-Biega lowland sector and 3350 (1420-5950) individuals in the Kasese survey areas. Within the same area, we estimate a population of 2600 (1620-4500) chimpanzees. Ape nestsite densities are significantly higher within the Kahuzi-Biega lowland sector than in the more remote Kasese survey area in spite of a significantly higher encounter rate of human sign within the lowland sector of the park. Comparison of our data with information obtained by Emlen and Schaller during the first rangewide survey of Grauer's gorillas in 1959 suggests that gorilla populations have remained stable in protected areas but declined in adjacent forest. These findings underscore the key role played by national parks in protecting biological resources in spite of the recent political and economic turmoil in the region. We also show that forest reconnaissance is a reliable and cost-effective method to assess gorilla densities in remote forested areas

Results of Fitting a Logistic Regression Model to Elephant and Human Presence/Absence Data for Each MIKE Survey Site Separately

<p>Distance to road (in kilometres) was used as the explanatory variable (except for probability of elephant occurrence for Minkébé where modelling is not required due to an effective probability of 1). Elephant data are shown to the left, and human data to the right. The observations and regression lines are colour-coded by site, and the 95% confidence interval is indicated by the dotted lines. The probability of elephant occurrence is significantly related to distance to road for all sites except Minkébé and Salonga. Due to the imprecision in the data and other influences not captured by distance to road, the probability of human presence is only significantly related to distance to road for the Ndoki-Dzanga site for the separate site analyses.</p

Results of Fitting a Logistic Regression Model to Elephant and Human Presence/Absence Megatransect Data

<p>Distance to road (in kilometres) and location within or outside the protected areas were used as explanatory variables. (A) shows the elephant data, and (B) shows the human data. The observations and regression lines are colour-coded to correspond to within or outside the protected areas and the dashed line shows the regression line with only the distance to road covariate. The covariates distance to road and location within or outside the protected areas are significant for both elephant and human probability of occurrence.</p

MIKE Survey Sites and the Megatransect

<p>Note that the since the Dzanga-Sangha and Nouabalé-Ndoki MIKE sites comprise a contiguous forest block, they were combined into a single unit (Ndoki-Dzanga) for analytical purposes.</p

Interpolated Elephant Dung Count and Human-Sign Frequency across the Ndoki-Dzanga MIKE Site

<p>Increasing colour intensity signifies increasing dung and human-sign frequency.</p

Estimated Conditional Dependence of Elephant Dung-Pile Numbers on Distance to Road (in Kilometres)

<p>Estimates (solid line) and confidence intervals (dashed lines), with a rug plot indicating observation density along the bottom of the plot, are shown. To avoid over-fitting, the degrees of freedom were restricted to two for the distance-to-road covariate.</p