Interference competition between sunbirds and carpenter bees for the nectar of Hypoestes aristata

Interference competition for nectar sources has been repeatedly described between hummingbirds and various insects, but rarely recorded in other nectari-vorous birds. We observed aggressive behaviour by African sunbirds (Cinnyris reichenowi and Cinnyris bouvieri) defending the nectar plant Hypoestes aristata against carpenter bees (Xylocopa caffra and Xylocopa inconstans) in the Bamenda Highlands, Cameroon. During 200 hours of observation, we recorded 38 cases of the sunbirds attacking carpenter bees; all these intrusions occurred only in the flower-richest patches of the plant. We predict that similar aggressive interactions will occur between other Old World nectarivorous birds and insects. Such interference competition between distantly related taxa could have an important impact on the evolution of pollination systems.     

Phylogeny and nitrogen fixation potential of Bradyrhizobium species isolated from the legume cover crop Pueraria phaseoloides (Roxb.) Benth. in Eastern Cameroon

Pueraria is an herbaceous, perennial legume crop originating in Asia. Pueraria phaseoloides (Roxb.) Benth. (tropical kudzu) is frequently introduced into production systems and is used as green manure, a cover crop and a forage plant, making it important economically. We used P. phaseoloides as a trap crop to study and characterize soil rhizobia in Eastern Cameroon. Bacteria were isolated from fresh nodules collected from field-grown P. phaseoloides roots. The 16S-23S rRNA internal transcribed spacer (ITS) sequences from 30 bacterial isolates were amplified by polymerase chain reaction (PCR) and the reaction products were sequenced. Phylogenetic analysis revealed that all isolates were ascribed to the genus Bradyrhizobium and were grouped into three clusters of Bradyrhizobium sp. strains, one cluster of B. yuanmingense strains, and one cluster of B. elkanii strains. Acetylene reduction assay (ARA) results indicated that the B. yuanmingense strains had significantly higher nitrogen fixation potential and that they could be used as inoculants to enhance nitrogen fixation in Pueraria grown in Eastern Cameroon.     

Enrichment of logging gaps with moabi (Baillonella toxisperma Pierre) in a Central African rain forest

Studies of regeneration in African rain forests suggest that without silvicultural treatments, natural succession in logging gaps may not result in the establishment of timber species. In this paper we present the results of an experimental enrichment planting with moabi (Baillonella toxisperma Pierre), a valuable and important timber species harvested in Central Africa. Although forest gaps are generally considered as favourable for the regeneration of this species, a survey conducted in a forest concession in south-eastern Cameroon provided an estimate of only 12.7 seedlings ha⁻¹, suggesting that the species was, in fact, poorly represented in logging gaps within the study area. To further investigate the dynamics of the moabi in logging gaps, 795 seeds were sown in 15 logging gaps and 410 nursery-raised seedlings were planted in 15 other gaps. A biannual monitoring program over a 30-month period showed a lower survival rate for seedlings from sowing (75.9%) compared to that of nursery-raised seedlings (95.3%). Planted seedlings reached an average of 229.3 cm tall whereas seedlings from sowing were 167.5 cm tall, with the observed difference roughly corresponding to the average height of the nursery-raised seedlings at the time they were introduced to the logging gaps. After 30 months, the diameters of planted seedlings (16.8 mm) were also greater than those of the directly sown individuals (12.5 mm). Forest gap characteristics significantly influenced the growth of the plants. Factors accounting for the differences were total solar radiation, the soil content of coarse sand, the topographic position of the gap, the vegetation cover and the density of Macaranga spp. Whilst total solar radiation had a positive influence on growth, the remaining factors had impacted growth negatively. A streamlined technique was tested by planting 7 seedlings in 250 gaps. Without additional site maintenance, 29.3% of the moabi seedlings emerged naturally from the competing vegetation after 24 months. With biannual maintenance some 89.4% of seedlings became successfully established. Clearance operations had no significant influence on the height of plants whilst plant diameter was greater in cleared gaps. The total cost of the enrichment technique was 5.5 EUR per gap without maintenance and 7.5 EUR per gap with a single maintenance measure. Whilst long-term monitoring is needed, this study suggests a high survival rate of moabi introduced in logging gaps, and a growth rate 10 times higher than previously reported under canopy cover. These findings, combined with the low costs of the enrichment technique, support the use of silvicultural measures in logging gaps to restore the forest.     

Effects of different land management techniques on selected topsoil properties of a forest Ferralsol

Soil erosion is a major threat for Ferralsols in Cameroon. The influence of traditional intercropping (TI), disk-harrow ploughing (DH), no-tillage (NT), and Wischmeier bare fallow (BF) on runoff coefficient, soil loss, organic carbon (OC) content and bulk density was evaluated in topsoils of a forest Ferralsol in Yaoundé region, Central Cameroon, using erosion plots. This was to ensure the best conditions for the determination of the soil properties to be assessed. After two years of cropping, the mean runoff coefficient remained very low for TI (<2% of the rain) as compared with NT (14%) and DH (15%). The same held true for soil loss which was in the order of 2, 68 and 109 Mg ha⁻¹ for TI, NT, and DH respectively, and bulk density which was 1.06, 1.18 and 1.21 Mg m⁻³ respectively. Comparing the latter with the measurements obtained from BF (1.23 Mg m⁻³) and the adjacent secondary forest (SF) (1.04 Mg m⁻³) showed that the disk-harrow treatment was the most degraded among the three. The same comparison was made for the OC content. It was found that while in SF, OC was as high as 30 g kg⁻¹, it was only 11, 13, 15 and 18 g kg⁻¹ in BF, DH, TI, and NT respectively. On the average and for the time frame considered, TI adversely affected topsoil properties less than NT, DH and BF in this order. Based on the above, it can be concluded that TI is more conservative than the three other land management techniques investigated.     

Getting to grips with the magnitude of exploitation: Bushmeat in the Cross-Sanaga rivers region, Nigeria and Cameroon

Wild meat harvests in African moist forests are presumed to exceed production, even in the case of traditional societies still using rudimentary hunting methods. Though some approximations do exist of the volume of bushmeat harvested in some Central African moist forest areas, estimates based on extensive and simultaneous sampling, within a large geographical region, are not available. Here, we present the results of the first reported study of this kind. During a period of 5 month, we counted bushmeat carcasses deposited in 89 urban and rural markets in a 35,000 km² area between the Cross River in Nigeria and the Sanaga River in Cameroon. We used these data to calculate annual bushmeat volume traded by site, species and overall in the study area.Mammals represented >90% of the bushmeat carcasses sold in all sites. Reptiles were also abundant, but birds and amphibians were relatively scarce. Estimates of carcasses extracted and crude biomass per site varied significantly between countries. In Nigeria, biomass (kg) extracted for sale per km² per year, was three times greater (600 kg/km²) than in Cameroon. Conservative estimates for the entire study area indicate that >900,000 reptiles, birds and mammals are sold each year by the rural and urban population, corresponding to around 12,000 tonnes of terrestrial vertebrates. We also assessed the relationship between bushmeat harvested for sale and distance of the study settlements from the main protected areas (Cross River and Korup National Parks). The number of carcasses and biomass sold was negatively related to the proximity to the national parks in >50% of species in Nigeria, and in 40% of species in Cameroon.Our cross-site comparison documents the staggering volume of wild species affected by hunting in the region. We also conclude that species within the main protected areas in both countries are likely to be negatively affected by the current and future demand for bushmeat in the surrounding areas.     

Effects of storage and incubation temperature on the viability of eggs, embryos and larvae in two strains of an African catfish, Heterobranchus longifilis (Siluriformes, Clariidae)

Two experiments, dealing with short‐term storage of ova and thermal conditions to optimize gamete and eggs management in hatcheries of the African catfish, Heterobranchus longifilis, were carried out. In the first experiment, ova collected by stripping from two strains of H. longifilis were stored for intervals up to 8 h at two temperature regimes: in a domestic refrigerator (3–5°C) and at ambient room temperature (20.5–22°C). In the second experiment, eggs were incubated from fertilization to hatching at different experimental temperatures (21, 25, 29, 32 and 35°C) to determine the effects of temperature on the kinetics of white egg appearance, hatching times and hatching quality. Gamete storage at warmer temperatures significantly prolonged viability irrespective of the strain used. In fact, the hatching rate for ova stored at 20.5–22 and 3–5°C for 5 h ranged between 75.2–79.3% and 6.5–9.4% respectively. Loss of viability was most noticeable after 6 h storage at ambient room temperature. Post‐storage viability significantly declined after 2 h exposure to the domestic refrigerator temperature. No hatching of normal larvae took place after 8 h post‐storage time. Results from the second experiment showed that time to maximum whitening of eggs was both strain‐ and temperature‐dependent. The time to maximum mortality of eggs was shorter in the Layo strain (LS) than in the Noun strain (NS), regardless of incubation temperature. The appearance of white eggs was shorter with increasing incubation temperatures. Hatching times decreased with increasing temperature, regardless of strain. Hatching took place from 21 to 27 h and 19 to 24 h after fertilization at temperature of 29°C, respectively, for NS and LS. The length of the hatching period was remarkably shorter for LS than NS at any tested incubation temperature, except 35°C. No hatching took place at 21°C. The highest proportion of normal larvae occurred at 25 and 29°C, respectively, for NS and LS. Hatching rate was highest at 25 and 29°C, respectively, for NS and LS. There was a significantly higher proportion of deformed larvae at 35°C regardless of the strain.     

Foot and Mouth Disease and Livestock Husbandry Practices in the Adamawa Province of Cameroon

Foot and mouth disease (FMD) is a highly contagious viral disease of even-toed ungulates and is endemic in most of the tropics. A cross-sectional study using a stratified, two-stage random sample design was undertaken in the Adamawa Province of Cameroon. The objectives were to measure the reported herd-level prevalence of FMD and a range of husbandry practices important for its transmission. The owner-reported prevalence for the previous 12 months was 57.9% (50.4–65.4%), although there was a significant variation across the Province. During the previous dry season, 46.5% (38.6–54.4%) of herds had gone on transhumance. Herds had high numbers of contacts with other herds while on transhumance (98.6%), at pasture (95.8%) and at night (74.4%), with medians of 7–10, 4–6 and 1–3 daily contacts, respectively. The high level of endemic FMD and potential for disease spread presents a significant challenge for control and eradication. Locally sustainable methods need to be developed upon which larger regional control programmes could be built in the future.     

Post vaccination and colostral peste des petits ruminants antibody dynamics in research flocks of Kirdi goats and Foulbe sheep of north Cameroon

We studied Kirdi goats and Foulbe sheep kept on-station at the Institute of Agricultural Research for Development (IRAD), Garoua to look at their immunological response following vaccination with a specific peste des petits ruminant (PPR) virus vaccine. Pre-vaccination PPR antibody seroprevalences were 44 and 29% in goats and sheep, respectively. Seroprevalences following vaccination were 100% in both species. Titres remained above the protection threshold level (1:10) in both species at 12 months. Maternal antibodies in young animals were detectable to up to 6 months of age but fell below the protection threshold level at 3.5 and 4.5 months in lambs and kids, respectively. Kids and lambs from immunised or exposed dams should be vaccinated at 4 and 5 months of age, respectively.