Social structure and life-history patterns in western gorillas (Gorilla gorilla gorilla)

Life-history traits and ecological conditions have an important influence on primate social systems. Most of what we know about the life-history patterns and social structure of gorillas comes from studies of eastern gorillas (Gorilla beringei sp.), which live under dramatically different ecological conditions compared to western gorillas (Gorilla gorilla sp.). In this paper we present new data on western gorilla social structure and life histories from four study sites, and make comparisons with eastern gorilla populations. Data were obtained from two study sites with gorilla groups undergoing the habituation process (Lossi, Democratic Republic of Congo and Bai Hokou, Central African Republic) and two "bai" studies (Maya Nord and Mbeli Bai, Republic of Congo). The size and structure of these groups were similar to those seen in eastern gorillas. However, differences in the occurrence of various group transitions (group formations, changes between one-male and multimale composition, and group disintegrations) exist, and western gorillas notably exhibit much higher rates of male emigration and correspondingly fewer multimale groups compared to mountain gorillas. Certain phenomena have been observed only rarely, including predation by leopards. The preliminary data show no significant differences in birth rates between western gorillas and mountain gorillas. The ecological variability across gorilla habitats likely explains the flexibility in the social system of gorillas, but we need more information on the social relationships and ecology of western gorillas to elucidate the causes for the similarities and differences between western and eastern gorillas on the levels of individuals, social groups, and population dynamics.

Mineral content as a basis for food selection by western lowland gorillas in a forest clearing

The forests in northwest Republic of Congo contain a number of herbaceous swamp clearings that provide foraging sites for lowland gorillas (G.g. gorilla). A 10-month study at the Maya Nord clearing (Parc National d'Odzala) showed that feeding activities occupied 72% of the time visiting gorillas spent on the clearing. They fed on four plant species: Enydra fluctuans (Asteraceae), Cyperus sp., Pycreus mundtii, and Rhynchospora corymbosa (Cyperaceae) among the 45 species recorded on the clearing. These clearing food species have higher mineral contents (especially Na and Ca) than the dominant Marantaceae species (Haumania liebrechtsiana) that constituted a staple food plant for gorillas in this forest. They also have higher potassium contents and contain less lignin than non-eaten clearing items/species. Finally, the most actively searched for clearing food (Enydra fluctuans) was characterized by the highest amount of Na and Ca. These results suggest that the mineral content (especially in Na, Ca, and/or K) could determine the feeding selectivity of gorillas at the clearing. They also tend to confirm that the amount of fiber plays a deterrent role in food selectivity, as has been found by many authors. The high density of gorillas in that region could result from the combination of the large areas of Marantaceae forests that provide abundant though monotonous food, and the number of clearings that provide sufficient mineral supplies. Clearings should thus be considered as key habitats for the conservation of gorillas.

Grouping patterns, reproduction, and dispersal in a population of sitatungas (Tragelaphus spekei gratus)

A population of sitatungas (Tragelaphus spekei gratus) living in a forest swamp clearing, Maya Nord, in the Republic of Congo was studied over 3½ years and its grouping patterns and population dynamics were analysed. The sitatungas in this clearing formed a stable group, which remained in residence. The group (16–36 individuals) functioned like a harem. As a result of intrasexual competition, all the males and some of the females born at Maya left the group before reaching sexual maturity. We hypothesize that this large grouping resulted from the development of a tendency for females to be gregarious for reasons related to food availability. This tendency, combined with an aseasonal pattern of reproduction, favours direct monopolization of females by one male. Social and mating strategies observed at Maya fit the model of "female-defence polygyny" (Emlen and Oring). Our results provide an argument in favour of relating food availability and grouping patterns, and underline the plasticity of social organization and mating strategies in sitatungas.

Population structure and group composition of western lowland gorillas in north-western Republic of Congo

Population studies are an essential part of conservation actions. Under exceptional observation conditions we studied a western lowland gorilla population visiting the Maya salt-clearing (north of the Parc national d'Odzala, P.N.O., Congo) over an 8 month period; 36 groups and 18 solitary individuals (a total of 420 individuals) have been identified visiting the clearing, which suggests a high gorilla density in the region. Ninety-six percent of the gorillas entered the clearing in groups. One-male groups had a mean size of 11.2. Ninety percent of solitary individuals were silver-back males. Compared with other populations of both lowland gorillas and mountain gorillas, the Maya population had the highest immature rate and the highest number of infants per female. Ecological correlates that could explain the attractiveness of the Maya clearing are discussed. The present status and the renewal rate of the Maya population indicate the need for further studies and confirm the importance of developing eco-tourism in this region as part of the sustainable park management activities developed by the ECOFAC programme (European Union). The results also provide arguments to support the proposal for extending the P.N.O. to include this region, which is rich in salt-clearings and attracts many other key-species of mammal such as forest elephants.

Characterization of the mucins produced by normal human colonocytes in primary culture

Mature goblet cells filled with mucin ready for secretion represent about one third of the cells in primary cultures of human colonocytes. In the present study characterization of the mucins produced by cultured human colonocytes was made by histochemical methods by lectin and monoclonal antibody binding. Two monoclonal antibodies and three lectins (Dolichos biflorus (DBA), Helix pomatia (HPA) and Arachis hypogea (PNA) recognizing epitopes or sugar haptens characteristic of different stages of mucin glycoprotein maturation, were employed. The reactivity to these probes was tested both on cultured colonocytes and on tissue sections of the normal colon mucosa. The results show that the mucins produced in culture are glycosylated to the mature form, as they show the same reactivity to lectins and antibodies of the mucins expressed in tissue sections of the normal colon mucosa. In addition, it is demonstrated that cultured human colonocytes do not express mucins reactive to PNA, which are characteristic of tumors. Since the cultured colonocytes maintain the expression of differentiated functions for at least three days, they may offer a useful model to study metabolism, function and regulation of colon mucins in health and disease.

Human colonocytes in primary culture: a model to study epithelial growth, metabolism and differentiation

The purpose of this work was to set up an in vitro model for the study of normal and pathological functions of the colonic epithelium. We have isolated colonic crypts by mild proteolytic digestion and mechanical dissociation of human biopsy material obtained during colonoscopy. The crypts, free of connective tissue, when placed in culture rapidly attached to the substrate and formed colonies containing over 95% of epithelial cells. Histochemical and ultrastructural characterization of the colonies showed the presence of both absorptive and secretory cells, exhibiting a high degree of differentiation. Proliferative activity occurred mostly during the first 24 h and progressively declined thereafter. The cells survived and maintained differentiated characteristics for at least three days in culture. This method can be used to study normal functions of the colonic epithelium. It may also be employed to investigate both noxious and protective factors in pathological conditions such as inflammatory bowel disease and colorectal neoplasia.

[A case of multiple intestinal perforations due to TBC in a female patient with HIV-1 infection]

The authors report a case of HIV-1 infection, primary miliary tuberculosis of the lung and secondary intestinal tuberculosis complicated with multiple intestinal perforations. The surgical emergency therapy, supported by specific antitubercular drugs, antibiotics, and total parenteral nutrition, consisted in suturing seven perforative sites of the small and large intestine. The Authors stress the possibility that in the future tubercular complications up till now considered atypical may become more and more frequent because of the HIV-1 infection association.