Annie Gautier-Hion

Diets of two sympatric colobines in zaire : more evidence on seed-eating in forests on poor soils

Recent studies have shown that the so- called folivorous African colobines eat a significant amount of seeds. There is disagreement as to whether seed-eating is due to the poor quality of tree foliage, due in turn to poor soils, or to the fact that seeds are a normal part of colobine diets. To test these hypotheses, we studied feeding of red colobus monkeys, Colobus badius tholloni,and black-and-white colobus monkeys, Colobus angolensis angolensis,in a tropical rain forest of Central Zaire (Salonga National Park). We conducted studies on soil properties, vegetation composition, and the availability and chemical contents of food plants simultaneously. Soils were very acid, with a high percentage of sand, very low cation exchange capacity, and very low exchangeable bases. The forest was dominated by legumes (45.6% of trees), among which the Caesalpinioideae were the best represented (85%). C. badiusfed mostly on leaves (61%) and seeds (33%), legumes making up 65% of their diet. C. angolensisfed mostly on seeds (50%) and leaves (27%); 39% of their diet came from legumes. The two species tended to select items richer in crude protein or lipids or both. Total phenolics and condensed tannins were abundant in the foliage and seeds but were poor predictors of colobine choice of food. Intersite comparisons show that colobines in Zaire ate a higher proportion of seeds than all other related species so far studied in Africa and that the Salonga forest had among the poorest soils and harbored the highest percentage of Caesalpinioideae. Our results confirm that seed- eating is more common among colobines living in areas where soils are poor. They strongly suggest that this link is mediated through forest composition, especially the abundance of legumes, and that the development of seed- eating results both from the high availability of nutrient-rich seeds and from the poor quality of mature tree foliage.

Identification of Ebola virus sequences present as RNA or DNA in organs of terrestrial small mammals of the Central African Republic.

The life cycle of the Ebola (EBO) virus remains enigmatic. We tested for EBO virus in the organs of 242 small mammals captured during ecological studies in the Central African Republic. EBO virus glycoprotein or polymerase gene sequences were detected by reverse transcription PCR in RNA extracts of the organs of seven animals and by PCR in DNA extract of one animal. Neither live virus nor virus antigen was detected in any organ sample. Direct sequencing of amplicons identified the virus as being of the Zaire/Gabon subtype. Virus-like nucleocapsids were observed by electron microscopy in the cytoplasm of the spleen cells of one animal. The animals belonged to two genera of rodents (Muridae; Mus setulosus, Praomys sp1 and P. sp2) and one species of shrew (Soricidae; Sylvisorex ollula). These preliminary results provide evidence that common terrestrial small mammals living in peripheral forest areas have been in contact with the EBO virus and demonstrate the persistence of EBO virus RNA and DNA in the organs of the animals. Our findings should lead to better targeting of research into the life cycle of the EBO virus.

Variation in the Diets of Cercopithecus Species: Differences within Forests, among Forests, and across Species

Dietary data have been used to address numerous theoretical issues, yet we have little understanding of dietary flexibility in primates. Previous comparative research has either explicitly or implicitly assumed that the closer the phylogenetic proximity between two taxa, or the spatial proximity between two populations of the same taxon, the more similar their diets will be. We examine such assumptions by making dietary comparisons among arboreal Cercopithecus species at the intergroup, interdemic, interpopulational, and interspecific levels. Our analyses reveal considerable variation and sometimes the magnitude of the variation of particular contrasts is unexpected. We conclude that dietary flexibility blurs our traditional trophic assessment of primate species. Thus, a study of the diet of a single group, in a specific habitat, at one point in time may not be representative of the species as a whole. This flexibility suggests that a profitable avenue of future research is quantifying the degree of flexibility that different primate lineages have in their digestive strategies.

Population structure and group composition of western lowland gorillas in North-Western Republic of Congos

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 dOdzala, 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. Am. J. Primatol. 48:1–14, 1999.

Primate diet and biomass in relation to vegetation composition and fruiting phenology in a rain forest in Gabon

To test the hypothesis that primate populations are limited by food resources, we studied the feeding ecology of three cercopithecines and one colobine in a rain forest in central Gabon. Simultaneously, we monitored the fruiting phenology of trees and estimated the biomass of the monkey community. The Makandé Forest is dominated by Caesalpiniaceae and characterized by a lack of secondary vegetation and of trees species producing fleshy fruits. Fruit production was irregular intra- and interannually. Fruiting peaks of dry fruits (mainly Caesalpiniaceae) and of fleshy fruits occurred at the same period. However, interseasonal and interannual variability was greater in Caesalpiniaceae than in other families. As a result, the Makandé forest is subject to bottlenecks when food is scarce. On an annual basis, seeds (primarily Caesalpiniaceae) dominated the diet of all monkeys. On a seasonal basis, cercopithecines preferentially consumed fleshy fruits as long as they were available, whereas colobines increased consumption of young leaves when seed availability declined. The consumption of mature leaves was low. The monkey community biomass (ca. 204 kg/km2) is one of the lowest in Central Africa. We suggest that both cercopithecine and colobine populations are limited as a result of the combined effect of the dominance of Caesalpiniaceae, which provide dry fruits according to a mast-fruiting pattern and mature leaves of low quality, and the lack of seral successional stages, which provide fleshy fruit on a more regular pattern and leaves of better quality. During the period of food scarcity, cercopithecines should suffer from the low availability of fleshy fruit, which are their favorite food. At the same period, colobines should be limited by the low availability of edible leaves. Similar low primate biomasses are found in forests dominated by Caesalpiniaceae or Lecythidaceae in South America and in Dipterocarpaceae forests in South Asia, which suggests that their biological characteristics, in particular dry fruits and mast fruiting, are unfavorable to monkey populations. Our results confirm that habitat mosaics may support larger populations of primary consumers than homogeneous primary forests can.

Seminomadic Ranging in a Population of Black Colobus (Colobus satanas) in Gabon and its Ecological Correlates

We observed ranging patterns in a black colobus population in the Forêt des Abeilles, Central Gabon. We compared the results with those for two other populations (Lopé Reserve in Central Gabon, Douala-Edéa in coastal Cameroun) in order to estimate the extent of specific variability in population structure and ranging behavior and to identify ecological factors influencing interpopulation differences. The mean number of monkeys in a group is 17, and all groups had a multimale structure. Home ranges were large, and the fact that they continued to increase with increasing number of observations indicated that the monkeys did not frequently resample their habitat. Ranging patterns varied according to the staple food consumed: distances travelled daily increased with increasing seed intake and decreased with increasing leaf intake. The ranging patterns of groups of Colobus satanas are seminomadic. Up to 6 or 7 groups shared the same space, and two group ranges could overlap by as much as 65–75%. Comparisons with the two populations previously studied showed that group size and group structure are broadly similar. At all three sites, black colobus were mainly seed eaters and ate large amounts of leaves in the season of fruit shortage. In the Forêt des Abeilles, however, group home ranges were much larger than at other sites, and this population had the lowest density. This is correlated with vegetation composition and with harshness of the main dry season. This colobus population appears limited by both recurring food shortage in the dry season and episodic periods of seed shortage resulting from irregular fruiting of the dominant family Caesalpiniaceae. Their seminomadic ranging would constitute the least costly strategy to cope with the low carrying capacity of their habitat.

Seed dispersal versus seed predation: an inter-site comparison of two related African monkeys

C. pogonias and C. wolfi plant diets were studied in two sites, in Gabon and Zaire and compared with fruit availabilities. Monkeys in Gabon were found to be mainly fruit pulp-eaters while monkeys in Zaire were alternately seed-eaters, aril-eaters or leaf-eaters. These differences were related to differences in the availability of fruit categories: fleshy fruits were found to be much more abundant in Gabon than in Zaire forests. As a result, monkeys in Gabon were found to be mainly seed-dispersers while monkeys in Zaire were found, to a large extent, to be seed-predators. Results are discussed in terms of phenotypic flexibility in monkey feeding behavior, diversity of plant-monkey interactions, geographic variability of keystone plant resources, and their implications for forest management practices. The low availability of fleshy fruit species in Zaire is hypothezized to result from the poor soil conditions.

Mutualism between a leguminous tree and large African monkeys as pollinators

Observations of a monkey community in a forest of the Zaire Basin show that four species intensively lick the nectar of Daniellia pynaertii (Caesalpinoideae) for 5 months of the year; nectar makes up a mean of 20% and a maximum of 50% of monthly plant feeding records (Fig. 3). Such intensive nectar-feeding by monkeys of up to 8 kg body weight probably developed in these basically frugivorous primates as an alternative strategy to cope with a shortage of fleshy fruits. This would have been possible due to the high density of the plant species, the synchrony and abundance of its flowering (Fig. 2), and the large size of the nectar drop and its nutritional value. Patterns of monkey movements among Daniellia trees show that one flowering tree may receive up to 10 species visits and 30 individual visits per day, for a total of up to 141 min. (Table 1). A monkey troop can visit 12 trees in succession over less than 3 h (Fig. 4). This suggests that monkeys are able to promote pollen transfer both among flowers of the same tree and between conspecific trees. The individual tree fruiting index is positively correlated with its flowering index and with the amount of visits by monkeys, indicating at least that monkeys do not inhibit the reproductive ability of flowers (Fig. 5). These results suggest that monkeys can be considered as a guild of effective pollinators. Long-term coevolution between the plant and its present-day pollinators seems unlikely, and we suggest that monkeys replaced other pollinators, such as Lepidoptera. This hypothesis is supported by the fact that tubular flowers adapted for pollination by Lepidoptera are found in affine species of the same genus and of affine genera, the latter being known to be pollinated by these insects. In contrast, D. pynaertii flowers typically meet the pollination syndrome currently defined for attracting large mammals: notably conspicuousness and open morphology of the flowers, nectar colour and abundance. These characteristics suggest that coadaptation between monkeys and plant or at least one-sided adaptation has operated.

Species composition, abundance and vertical stratification of a bat community (Megachiroptera: Pteropodidae) in a West African rain forest

A pteropodid bat community was surveyed in a West African rain forest using mist-nets set for 3 mo in 2 consecutive years (1996-97). The captures were carried out in the understorey and in the canopy for a total of 5054 mist-net hours and were analysed to answer three main questions: (1) to what extent does the bat assemblage vary along the vertical axis, (2) does the observed vertical stratification depend on wingspan (with largest bats preferring canopy openings to the cluttered understorey) and (3) was the vertical stratification repeatable from one year to the next? Nine bat species were reported, among which two were captured exclusively in the canopy where the total capture rate tended to be higher. The community structure did not differ between the four canopy stations. Four species significantly favoured canopy, two significantly favoured understorey and two were opportunistic regarding vertical stratification. Wing size and canopy-preference index were not significantly correlated and except for Eidolon helvum , index values for the 2 sampling years were correlated. Important inter-annual and seasonal variations of species richness and capture rate were observed and these are discussed in relation to rainfall patterns and migratory behaviour of the species concerned.

Do black colobus in mixed-species groups benefit from increased foraging efficiency?

Seed-eating in the African colobines varies according to species and site. Because seeds are more palatable than leaves, seed-eating is considered to result from a positive choice by colobines. A year-long study of the diet of Colobus satanas in Central Gabon confirmed that this species eats a significant amount of seeds. Furthermore, despite large variations in fruit availability, this amount consistently increases when colobines feed in mixed-species troops including frugivorous cercopithecines and mangabeys. Our results show that colobines benefit when feeding in mixed troops and suggest that polyspecific associations are an adaptive strategy that could have positive effects on colobine populations, especially during the period of fruit shortage.