Faecal analysis has proven to be a useful method of studying the diets of wild apes. This is especially true for populations living in tropical forest habitat in central Africa where dense vegetation makes systematic observation of feeding difficult. The method developed and used for faecal analysis in the Lopé Reserve, Gabon, where gorillas (Gorilla g. gorilla) and chimpanzees (Pan t. troglodytes) co-occur, are described and some examples given of some of the ways in which data can be qualified and analised. Faecal analysis alone cannot give a complete picture of diet as some foods leave no recognisable remains and others, particularly vegetative plant parts, are difficult to identify taxonomically. However, standard application of the methods allow some comparisons to be made between years, species and sites.

View full abstract

This paper presents methods chosen to sample forest structure and composition with a view to understanding the ranging patterns and habitat use by great apes, and suggests how data may be presented in simple yet meaningful ways. Straight-line transects were used to sample all tree >10 cm DBH within a 10 m strip. Although it may be difficult to make direct comparisons between study sites, it is relatively easy to compare some aspects of forest structure, species diversity, tree density, and the density of important food-sources in different forests. Several measures of diversity and food availability can be estimated using tree species frequencies and basal areas obtained from trancects, some of which are described here.

View full abstract

In order to analyze diets of eastern lowland gorillas, we used three method, such as belt transect methods, fecal analysis and tracking fresh feeding remains in our field works in Kahuzi Biega National Park, Zaire. This paper describes the detail procedure of each method. The long line method is useful for describing the composition and densities of plant species in different vegetation types. Fecal analysis is a useful means to quantify fruits and insects consumed by gorillas. It shows seasonal fluctuations in fruit consumption and age-sex differences in fruit and insect eating by eastern lowland gorillas. Tracking gorilla’s fresh feeding remains combined with fecal analysis is needed for describing the composition of diets. The various combination among these three methods contribute to day range of gorillas in relation to food availability, to a comparison of seed dispersion by gorillas, chimpanzees and elephants, and to a comparison of individual energy expenditure and food choice between seasons or between habitats. Some of the results analyzed by these methods are provided in this paper.

View full abstract

Individual density and social group formation of a western lowland gorilla population were estimated by (1) the line transect method with direct detection and (2) reconstruction of social groups from direct observation and bed count in the Ndoki Forest, northern Congo. The line transect method gave an estimate of 4-5 gorillas per sq km along the transect course in the roughly 24 sq km study site. The small range of the strip width in dense vegetation, detectability of all members in a group, uncovered vegetation type by the census course, and the contagious distribution of the animals in space may affect the results. The reconstruction suggested the presence of 7 social groups as well as solitaries in the same gorilla popUlation, although individual identification will be necessary for more accurate results. In other study sites of lowland gorillas, the densities have been reported to be lower in primary forests than those in secondary regenerating forests. Aboundant fibrous foods, such as certain aquatic plants found in the marshy grassland, may increase the carrying capacity and allow for the high density of gorillas in this primary forest,

View full abstract

The assessment of food abundance is critical to address many theoretical questions concerning chimpanzee ecology and social organization. A variety of methods have been used to estimate habitat-wide food abundance. Since methods vary between sites, it is difficult to make meaningful intersite comparisons, without calibration of the different methods.
We compare three methods used to estimate fruit abundance simultaneously in the Kibale Forest Reserve, Uganda. Estimates of fruit abundance derived from fruit traps were not related to estimates derived from either systematic transect sampling or estimates obtained from observing fruiting phenology of key species on a fruit trail. However, estimates based on fruit trail data and transect data were correlated.
We also report the results of surveys for herbaceous food availability using data from three different sites, employing similar, but not identical methods. The results of these analyses illustrate the difficulties encountered when data generated by divergent methods are compared, and we present specific recommendations as to how future studies might be structured to facilitate comparability between sites.

View full abstract

An analysis of 1231 nests from 163 nest-sites recorded during a twenty-seven month long study (August 1990-NovemberI992) on the feeding ecology oflowland gorillas at the Bai Hokou Study Site, Dzanga-Sangha Dense Forest Reserve, Central African Republic is presented and compared with results from a concurrent nest-count census at the same site as well as results from an earlier census of the regional population and those from other gorilla populations. Nest counts are commonly used 1) to estimate population sizes and densities (Tutin & Fernandez, 1984; Carroll, 1986, 1988; Fay, 1988; Fay & Agnagna, 1992) and 2) to supplement direct observations and thus aid in understanding fluctuations in the size and composition of gorilla groups (Kuroda, 1992; Mitani et. ai., 1993). At the Bai Hokou Study Site, 44 % of gorilla nests recorded during the longitudinal study had no construction. At 15% of nest sites none of the nests were constructed. During a fine-grained census of the same study area, 30% of the nests identified were bare ground nests. These results contrast with reports from other sites of 0-10% bare ground nests (Tutin & Fernandez, 1984; Williamson 1988; Carroll, 1986; Fay, 1988; Schaller 1963). Nest construction type is probably related to the availability of suitable nesting materials at the nest site and at 8ai Hokou is shown to be influenced by micro-habitat, season and group size. These factors are also likely to affect interpopulation variability in nest construction. Bare ground nests and associated dung generally deteriorate to become unrecognizable after 4 days, while other nest construction types remain recognizable for more than 50 days (Tutin & Fernandez 1984, this study). Therefore, nest-counts will generally underestimate the numbers of nests at sites older than 4 days and may even fail to record entire nest sites. The accuracy of nest-count surveys may thus vary with location, habitats sampled and season.

View full abstract