Frauke Fischer

Phytomass and fire occurrence along forest–savanna transects in the Comoé National Park, Ivory Coast

In tropical West Africa, distribution patterns of forest islands in savannas are influenced by fires which occur regularly in the grass stratum. Along continuous forest-savanna transects in the Comoe National Park, the change in the amount and composition of non-woody phytomass was investigated from savanna to forest interior. This was correlated with the cover of vegetation strata above, soil depth, and the occurrence of seasonal surface fires. Phytomass mainly consisted of leaf litter in the forests (about 400 g m -2 at the end of the rainy season, and about 600 g m -2 at the end of the dry season) and of grasses in the savanna (about 900 g m -2 ). Low grass biomass appeared to be primarily the result of suppression by competing woody species and not of shallow soil. The occurrence of early dry-season fires seemed to be determined mainly by the amount of grass biomass as fuel because fires occurred in almost all savanna plots while forest sites remained unaffected. However, late dry-season fires will encounter higher amounts of leaf litter raising fire probability in forests. Due to the importance of the amount of combustible phytomass, fire probability and intensity might increase with annual precipitation in both savanna and forest.

Decreases in ungulate population densities. Examples from the Comoé National Park, Ivory coast

In the Comoe National Park, Ivory Coast, there has been a tremendous decrease in all larger mammal species between 1978 and 1998. We document the degree of this decrease for the 11 most abundant ungulate species by comparing density estimates from two earlier studies undertaken in 1978 and 1984 with our own results from 1995 and 1998. Within the last 20 years all species included in the analysis experienced decreases between 60% and more than 90%. The species that suffered most were the duikers and other small antelopes up to the size of the kob antelope (Kobus kob kob). The larger decline of the smaller species also resulted in changes of the ungulate community, which in turn might affect other taxa such as large carnivores, and the entire ecosystem. The observed decreases can most likely be attributed to intensive poaching that occurred and still occurs throughout the park. Future conservation measures will hopefully stop this.

Distribution and status of the hippopotamids in the Ivory Coast

The distribution and relative abundance of the common hippo (Hippopotamus amphibius) and the pygmy hippo (Hexaprotodon liberiensis) was studied in the Ivory Coast between 1978 and 1986 by questionnaire survey, interviews, local field investigations and aerial censuses. In addition, the size of the pygmy hippo population in the Tai Forest area was monitored between 1995 and 2001. At the time of the initial study, the common hippo inhabited the Sassandra, Bandama and Comoé rivers, but was abundant only in the Upper Comoé. The pygmy hippo was restricted to the Guinean Forest zone between 7°25’N (Tiapleu Forest Reserve (Forêts Classée)) in the north and 4°18’W (estuary of the Agnebi River) in the east, where it was abundant in undisturbed rainforest areas. Population data are presented from the Comoé, Tai and Azagny national parks where the ecology of both species was studied in greater detail. The total popu lation of the common hippopotamus was estimated at about 1100 animals in 1978 1984, of which at least 70% concentrated during the dry season in the Upper Comoé, Leraba and Iringou rivers. The average dry season population density in the Comoé varied at that time between three and four animals per river kilometre, in groups of five to six, but had dropped to one to two per kilometre in 2002. During the rainy season hippos disperse upstream into smaller tributaries and downstream as far as the coast. As the forest zone is modified by forestry and agriculture, small herds of common hippos have become resident and in some localities are sympatric with the pygmy hippo. Pygmy hippos are solitary animals, confined to home ranges of 50 150 ha. In optimal habitat their population density can be as high as seven animals/km2, averaging about three animals/km2 over larger areas of undisturbed rainforest. At present, however, hunting pressure has reduced population densities to 0.8 2.5 animals/km2 even in the most favourable ecological conditions of the Tai National Park. Extrapolation of these densities suggests that the total population of pygmy hippos in the Ivory Coast is greater than previously thought, but does not exceed 15 000 animals. Most of these inhabit the Tai National Park and its adjacent protected areas. The remainder occur mainly in various forest reserves (Forêts classées). Ecological factors, which influence population density or limit pop ulation growth of the two different hippo species, are discussed and recommendations made for their conservation.

Timber plantations as favourite habitat for giant anteaters

Abstract The giant anteater (Myrmecophaga tridactyla) is generally considered a savannah inhabitant; little information exists on populations in forested areas as much as on most other aspects of its ecology. The aim of this study was to determine the ecological value of timber plantations to the species and its requirements of anthropogenically used and converted habitats. We investigated habitat use and distribution patterns of giant anteaters in Acacia mangium plantations in a northern Brazilian savannah biotope. Road counts were conducted to estimate anteater densities in two different habitats. Anteaters showed strong diurnal foraging activities in the plantations, and their densities were substantially higher there than in the surrounding savannah [plantations: 2.9 individuals (ind.)/km2; savannah: 0.1 ind./km2], with concentrations of up to 13.4 ind./km2. Although fundamental changes of anteater densities occurred on small scales in the plantations, no connection between anteater distribution and plantation management practices could be found. Food availability in Acacia plantations and cover from both extreme temperatures and potential predators probably make these forested areas well suited for giant anteaters. We conclude that conditions comparatively beneficial to the anteater can be found in natural forests but usually not in plantations of other exotic timber species. This needs to be incorporated in forestry management plans aiming at supporting this charismatic animal.

Seed Dispersal by South Africa's Only Forest-Dwelling Guenon, the Samango Monkey (Cercopithecus mitis)

Primate seed dispersal in South African forests and its potential benefit to forest plants has not been extensively investigated. South African forests are inhabited by only one exclusively forest-dwelling, large-bodied, diurnal, frugivorous primate, the samango monkey (Cercopithecus mitis). Our study presents first insights into seed dispersal by samango monkeys in an Afromontane forest in their northernmost South African distribution. Through focal animal sampling we found that samango monkeys were predominantly frugivorous (72% of observed feeding time), consuming fruits of 25 plant species and dispersing the seeds of 13 (52%) of them through defecation, carrying in cheek pouches and spitting and dropping. The overall ratio of seed predation was relatively low (16%). Although our study spanned the wet season only, our findings demonstrate that samango monkeys may be potentially important seed dispersers for certain plant species (Ficus spp. and Searsia chirindensis making up 44% of the diet) in this part of their range.