Termites are essential components of tropical ecosystems, in which they provide fundamental ecosystem services, such as decomposition of dead plant material, fostering of soil mineralization and provisioning of new microhabitats. We investigated the termite communities of four habitats in two protected areas in West Africa, which differ in management effectiveness: the strictly protected Lamto Reserve (LR) and the Marahoué National Park (MNP), which suffers from anthropogenic disturbance despite its protection status. We tested the effect of disturbance on species composition, richness and abundance as well as on functional (feeding type) composition. The effect of disturbance was clearly visible in the termite communities. Compared to the LR, the MNP had less termite species overall and in all habitats except the shrub savannah. Also the abundance of termites was generally reduced and a decrease of soil feeders recorded. The latter is well-known to be sensitive to anthropogenic disturbance in forests. Comparing our results with other studies, we were able to identify suitable bioindicators of ecosystem health for West-African savannahs. Furthermore, we discuss the potential consequences of anthropogenic disturbance on ecosystem services provided by termites.

The spatial distribution of canopy gaps was analysed on three sites (total 71 ha) in the tropical moist forest of Tai National Park, Ivory Coast. Pattern analysis revealed a clustered distribution of gaps for two of the three sites. Catena dependent gap formation processes might explain local differences in the occurrence and distribution of gaps. Gap densities, sizes and percentage forest area in gap phase are higher on the upper and middle slope than on the crest or lower slope. As a consequence, regeneration of gap dependent tree species might be directed to the catena positions with the highest disturbance regime. The spatial distribution of gap dependent species can be clumped, not only due to the regeneration within gaps, but also due to the clustered nature of gap distribution on its own.

An on-going controversy in community ecology involves the debate about the many factors that affect the assembly and composition of a given species assemblage. Theory suggests that community composition is influenced by environmental gradients or biotic processes. This study examines patterns of community composition in two tropical tree frog assemblages of primary and exploited lowland rain-forest sites in the Guiana Shield area of central Guyana, South America and the Upper Guinean rain-forest block of south-western Côte d'Ivoire, West Africa. We tested community composition and species abundance data of two adult tree frog communities collected on 21 standardized transects during a period of 5 y for evidence of spatial correlation in community composition. We applied simple and partial Mantel tests to separate the effects of environmental variables, spatial distance and spatial autocorrelation on community composition. Whenever environmental effects were accounted for, we found significant positive spatial correlation of community composition. All assemblages appeared to be spatially structured, i.e. sites in close proximity had similar species assemblages. However, spatially structured environmental variation (autocorrelation) did not account for the spatial structure of species incidence. Environmental factors did not prove to be significant predictors of species incidence in any of the assemblages analysed, even if we controlled for spatial effects. Observed correlation patterns of species composition were consistent within respective realms and disturbance regimes. Moreover, general correlation patterns were consistent between geographic regions. These results are in contrast to previously published results from a study on leaf-litter anurans and indicate that group-specific differences must not be neglected when analysing patterns of species composition in anurans as they may drastically alter the outcome of the analysis.

The population dynamics of the exotic earthworm Hyperiodrilus africanus was investigated in a secondary forest of the Natural Reserve of Lamto (Ivory Coast) over a period of 19 mo. The objectives were to assess seasonal abundance patterns and to determine the adaptive strategies of this species. Each month, 10 soil samples of 100×100×40 cm and 20 monolith samples of 25×25×30 cm were randomly excavated in a plot of 50×95 m and earthworms were extracted by both hand-sorting and wash-sieving methods. The results show significant inter-annual and seasonal fluctuations in population size. Three factors are likely to control population dynamics: (1) rainfall, (2) soil water content and (3) seasonality. The dry season appears to be the most important environmental factor that regulates population abundance when predation, density-dependent regulation and competition phenomena are ignored. Hyperiodrilus africanus exhibited an r strategy, suggesting a high ability to recover populations affected by drought.

To monitor the biodiversity quality of rainforest fragments in the eastern region of the Ivory Coast, the density of at least one important invertebrate group needs to be determined. This has been possible for nocturnal hunting spiders from the family Ctenidae using a novel combination of sampling and census techniques. The reflective characteristics of the eyes of these spiders meant that individuals were readily located using headlamps. Collections were made along transects (total length 5.5 km), adopting a distance sampling protocol. Density was estimated using distance sampling models. More than 2600 ctenids (15 species) were captured and identified. Seven of these species were present in sufficient numbers for density assessment. The combined density of these seven most common species in degraded forest fragments (0.124 m−2) was only half that in less disturbed forest (0.240 m−2). Ctenidae are a promising candidate for future monitoring of invertebrate groups in the rainforest.

In general, amphibian larvae dispose of nitrogenous wastes as ammonia and change to urea excretion during metamorphosis (Balinsky 1970). Ammonia excretion, however, poses a problem for tadpoles and embryos that live in a limited volume of fluid because it is toxic in higher concentrations. One solution is urea excretion or ureotelism. In amphibians it occurs in species with terrestrial modes of reproduction when larvae develop within the uterus as in the ovoviviparous Salamandra salamandra (Schindelmeiser & Greven 1981), when embryos develop in foam nests as in Leptodactylus bufonius (Shoemaker & McClanahan 1973), or when offspring develop in brood pouches as in Gastrotheca riobambae (Alcocer et al. 1992).

We studied activity patterns and habitat use by insectivorous bats in Comoé National Park, Ivory Coast. Bat foraging activity was quantified along five transects representing three different habitat types using acoustic monitoring and captures with mist nets and harp traps. Aerial insect abundance was assessed using a light trap; in addition shrub and tree arthropods were sampled. Bat activity was significantly and positively related to insect availability and ambient temperature, whereas increased visibility of the moon had a negative influence on flight activity. Together, these factors best explained both total bat activity and activity of bats hunting in open space and edge habitats. The interaction between temperature and light intensity was the best predictor of activity by species foraging in obstacle-rich forest habitats, however, the regression model had a low predictive value. Overall, a large proportion (c. 50%) of the variation in bat activity appeared to be a consequence of transect- and/or habitat-specific influences. We found a significant non-linear relationship between the activity of QCF (quasi-constant frequency) and FM–QCF (frequency modulated – quasi-constant frequency) bats and the phase of the moon, with lowest levels of activity occurring near full moon. We interpret this lunar-phobic behaviour as a reflection of a higher predation risk during moonlit periods. For FM (steep frequency modulated) and CF (constant frequency) bats, no significant correlation was found, although there was a trend suggesting that these bats at least were not negatively affected by bright moonlight. Foraging activity of bats was positively correlated with the abundance of atympanate moths; however, no such correlation was found for tympanate moths.

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.

The reproductive characteristics of Oreochromis niloticus, a multiple spawner, have been compared between populations submitted experimentally to three types of spatial structure. Fish from a same original stock were divided and reared for 2 months in: 1) concrete tanks with a bare bottom, 2) concrete tanks with a sandy bottom, or 3) concrete tanks equipped with an artificial reef. The females were then killed and their gonads examined for sexual stage and fecundity determination. Fecundity was inversely correlated to the spatial complexity of the environment whereas oocyte size tented to increase together with spatial complexity. Females placed in tanks with artificial reefs presented a lower fecundity and reproductive investment and bigger oocytes than those maintained in the bare bottom tanks. Fish reared in tanks with a sandy bottom had intermediate reproductive traits. The response of females to changes in the spatial structure of their environment was observed after only one or two reproductive cycles, providing the first experimental evidence of such rapid phenotypic adaptation to environmental complexity. The results also indicate that the perception of living space, arising from the availability of refuges and spawning sites, is more likely to influence the reproduction of tilapias than substrate quality.

A selection programme was set up in 1983 in the Ivory Coast to improve the growth and live weight of the indigenous Djallonkè sheep using an open nucleus breeding system. Selection was based on male individual weights at 80, 180 and 365 days of age. Multiple sires were used in farmers' flocks. Individual animal model, using average numerator relationship was used to estimate breeding values from which genetic trends were derived. This paper reports results of the analyses of 10 417 records of 80-day weights (WT80) of lambs born between 1984 and 1992 from 29 participating farmers, and 1978 and 849 records on 180- (WT180) and 365- (WT365) day weights, respectively, of lambs from the nucleus. Phenotypic trends exhibited substantial annual fluctuation during the study period. The heaviest weights were obtained in 1986 (10·1 kg) for WT80, 1984 (23·3 kg) for WT180 and 1985 (33·7 kg) for WT365. There was an annual decline of 152 g (P<0·05) in WT80 mainly (–180 g/year) due to negative environmental trend. The phenotypic and environmental trends for WT180 were –703 and –721 g/year, respectively, while the corresponding values for WT365 were –931 and –956 g/year. Overall mean weights of the ram lambs at the three ages were 9·9, 23·3 and 33·7 kg, respectively in the base year and 9·3, 17·8 and 28·2 kg, respectively in the final year. Breeding values increased by 28, 11 and 14 g/year for WT80, WT180 and WT365, respectively. Results of this study indicate that genetic progress can be made in growth performance of Djallonkè sheep if reasonable levels of animal management as well as selection pressure are maintained.

Data on Djallonke sheep collected from 1983 through 1992 on 29 participating farms of an open nucleus improvement programme and from the nucleus were analysed. Initial on-farm records on 14342 lambs and on-station records on 2551 ram lambs were edited down to 6605 for birth weight (BWT), 5857 for preselection (birth to 80 days) average daily gain (PSADG), 10417 for 80-day weight (WT80), 13054 for lamb survival at pre-selection, 1978 for 180 (WT180) and 849 for 365 (WT365) day weights. Year of birth, sire line, flock, month and season of birth had significant (at leastP < 0·05) effects on both on-farm and on-station weights and on lamb survival. Trait means were 2·2 (s.e. 0·02) kg for BWT, 69·6 (s.e. 1·26) g/day for PSADG, 9·1 (s.e. 0·05) kg for WT80, 19·7 (s.e. 0·24) kg for WT180 and 31·8 (s.e. 0·45) kg for WT365. Mean survival was 90 (s.e. 0·9) %. Single lambs were heavier at birth and at 80 days of age, grew faster to 80 days and were about 200 and 500 g heavier at 180 and 365 days respectively than multiple lambs. There was a large variation between flocks: flock means for WT80 varied from 6·4 to 12·0 kg (CV 0·21), with smaller flocks having generally the lowest means. Lambs born in the hot-rainy season had the heaviest birth and 80-day weights, whereas ram lambs born in the cool rainy and early hot-dry seasons had the heaviest 180- and 365-day weights. Lambs born during the cool months of July to October had the lowest survival rate. Multiplicative factors were found to be more appropriate for adjusting on-farm records for type of birth, management level, birth date, season of birth and ewe parity than additive adjustment factors.

Cette étude analyse le rôle de la seconde et petite saison d'upwelling dans les changements récents de l'écosystème pélagique côtier ivoiro-ghanéen. Depuis le début des années 1980, les captures de Sardinella aurita ont nettement augmenté au Ghana et en Côte-d'Ivoire ou les modifications de l'abondance et de la dynamique de l'espèce ont été les plus surprenantes. La taille des poissons a augmenté et l'activité reproductrice de l'espèce est maintenant d'une intensité équivalente pendant les deux saisons d'upwelling. On observe, entre 1970 et 1990, une tendance à la diminution de la différence entre l'intensité des deux saisons d'upwelling. Le rôle croissant de la petite saison d'upwelling dans l'écosystème permet de donner une interprétation aux changements observés. Cette saison, plus intense en Côte-d'Ivoire qu'au Ghana, intervient en effet pendant la période de l'année défavorable pour la productivité de l'écosystème pélagique et peut être comparée à un "goulot d'étranglement" pour cette productivité.

The larvae of Mussidia nigrivenella Ragonot, attack various fruits; it is the main maize cob borer in Ivory Coast. The development of attack during the cultivation, the behaviour of larvae in the field, the spatial distribution of eggs and larvae, the mortality of pre-imaginal instars and the annual fluctuations of populations are considered in this paper. This insect may represent an economical problem for seed producers in the south of the savannah area of Ivory Coast where its density exceeded 14 insects per cob, at harvest in 1984, whereas the risk of cob damaging by Mussidia nigrivenella appears to be very weak in the north and west of this region.

The main characteristics of the reproductive biology of Tilapia guineensis and Sarotherodon melanotheron have been studied in Ebrié lagoon (Ivory Coast), with a comparison between natural and cultured populations. In this lagoon, the two species breed throughout the year without interruption. However, seasonal variations in the intensity of the sexual activity have been observed and are more pronounced at the Layo aquaculture station, where the hydroclimate is more unstable than in other lagoon sectors studied. The proportion of mature individuals, the mean GSI, the relative fecundity and the spawning frequency are higher during the dry season than during the rainy season. In rearing enclosures, both species reach sexual maturity at a smaller size, and produce smaller but more numerous oocytes than in the wild. On the other hand, the relationship between the spawn weight and the female body weight are remarkably similar under both situations. For S. melanotheron, which is a male mouthbreeder, the number of brooded eggs or fry is positively related to the male body weight. In 2 m3 concrete tanks, the mean elapsed time between two successive spawnings is about 2 weeks for S. melanotheron and about 3 weeks for T. guineensis.

In intensive culture, the two species of brackish water tilapia, T. guineensis and S. melanotheron, have proved disappointing. Even under most favourable conditions, i. e. the monosex male culture of S. melanotheron, a poor growth rate (about 0.5 g.d−1) and a mediocre feed conversion do not presage a profitable aquaculture exploitation. On the other hand, extensive culture trials using the original "acadja-enclosure" technique have given very encouraging results. Annual fish yields of more than 8 t/ha, including 70 to 80% of S. melanotheron of marketable size, are possible without any artificial feeding.

Ground spraying trials involving three synthetic pyrethroids: OMS 2012 (BAY FCR 1272, cyfluthrin) w.p. 10%, OMS 2013 (BAY NAK 1654, fenfluthrin) w.p. 5%, OMS 3004 (WL 85871, alphamethrin) w.p. 5%, were carried out in January 1984 against G. palpalis palpalis and G. tachinoides in the Bouaflé human trypanosomiasis focus, Ivory Coast. Two dosages of each formulation were tested as residual spray: 12 g of active ingredient (a.i.) per hectare at a concentration of 0.016% and 48 g (a.i.)/ha at 0.064%, The insecticide was applied by means of the atomiser SOLO PORT 423 and the total area treated was estimated at 29 ha. The results were evaluated during 5 months with Challier—Laveissière biconical traps.

OMS 2013 w.p. 5% at 12 g (a.i.)/ha, had unsatisfactory effect on G. palpalis palpalis and G. tachinoides from the first month after spray. At 48 g (a.i.)/ha this formulation showed a moderate effect on both vectors during the first 3 months after treatment, rate of reduction in apparent density by trapping (A.D.T.) varying between 70 and 90%.

OMS 2012 w.p. 10% at 48 g (a.i.)/ha gave satisfactory results, 92% reduction in A.D.T. of G. p. palpalis during the first 3 months after treatment. OMS 2012 w.p. 10% at 12 g (a.i.)/ha gave 94% reduction in A.D.T. of G. tachinoides during the first 2 months after treatment. At the dosage of 48 g (a.i.)/ha, 97% reduction in A.D.T. of G. tachinoides was recorded through the evaluation period.

OMS 3004 w.p. 5% at 12 g (a.i.)/ha, gave 97% reduction in A.D.T. of G. palpalis palpalis during the first 3 months after treatment. At 48 g (a.i.)/ha, 91–98% reduction in apparent density of G. p. palpalis was achieved during the period of evaluation. The effect of this formulation at 12 g (a.i.)/ha on G. tachinoides, was very pronounced during the first 3 months after treatment, being 99% reduction in A.D.T. At 48 g (a.i.)/ha, 100% reduction was obtained during the first 4 months and more than 99% reduction in 5 months after spray.

Ground spraying trials involving a new formulation of synthetic pyrethroid, alphamethrin (OMS 3004, WL 85 871) e.c. 10% were carried out in January 1983 against G. palpalis palpalis in the Bouaflé human trypanosomiasis focus, Ivory Coast. Four dosages were tested in five localities: 12 g of active ingredient (a.i.) per hectare; 24, 36 and 48 g (a.i.)/ha. Each dosage was applied once as a residual spray. The atomiser SOLO PORT 423 was used for spraying and the total area treated was estimated at 20 ha.

The results were evaluated with Challier-Laveissière biconical traps. The knock-down and short term effects of the insecticide were very satisfactory, 96–100% reduction in apparent density of the vector obtained with all the four dosages applied during the first 2 months after treatment.

Three to five months after spraying, more than 98% reduction in apparent density of G. palpalis palpalis was achieved even with the lowest dosage of 12 g (a.i.)/ha. The highest dosages tested did not seem to increase the persistence of the insecticide nor the mortality rate of the vector in the study area.

Due to adverse side effects on man at high dosages during and after treatment, it is recommended that in residual ground spraying, alphamethrin e.c. 10% be applied at a maximum dosage of 12 g (a.i.)/ha and at a concentration not exceeding 0.016% of active ingredient.

Ground spraying trials with different dosages of deltamethrin wettable poweder (NRDC 161) were carried out against G. palpalis (s.l.), vector of sleeping sickness, in January and November 1981 in the Bouaflé human trypanosomiasis focus, Ivory Coast. Three dosages have been tested: 60 g of active ingredient (a.i.) per ha at a concentration of 0.08% in January; and 20 and 12 g of active ingredient per ha in November at 0.027 and 0.016%, respectively. Each dosage has been applied once as a residual spray; spraying apparatus used was the atomiser Solo Port 423. The knock-down and short-term effects of the insecticide were very satisfactory: 90–98% reduction in apparent density of the vector was obtained during the first 2 months after treatment with all the three dosages applied. In the long term, 2–4 months after spraying, more than 95% reduction in apparent density of G. palpalis (s.l.) was achieved even with the lowest dosage of 12 g (a.i.)/ha. The highest dosage of 60 g (a.i.)/ha does not seem to increase significantly the persistence of the insecticide nor the mortality rate of the vector in the study area. In order to reduce the cost of a tsetse control programme and also to minimise insecticide impact on non-target organisms, it is therefore recommended that deltamethrin w.p. be applied at the lower dosage of 12 g (a.i.)/ha in residual ground spraying.