Foraging behaviour of equatorial Afrotropical stingless bees: habitat selection and competition for resources

This thesis is a result of fieldwork on foraging ecology of Afrotropical stingless bees in Uganda. This is because most studies on stingless bee ecology are largely based in South America and South-east Asia and have ignored the aspects of Afrotropical stingless bees. The central question is how the Afrotropical bees co-exist by partitioning their resources. Aspects of nesting behaviour of the stingless bees are presented in chapter 3. In BINP there are at least five stingless bee species belonging to two genera: Meliponula (four species) and Hypotrigona (one). The bee species nest in tree cavities, mud house wall crevices and underground. The relative importance of predation, food supply, nesting site and elevation affecting abundance of stingless bees were studied for meliponines in chapter 4. Predators were treated more comprehensively compared to previous field studies. Our figures for nest density for both the honey bee and the combined stingless bee species may agree with estimates from drier parts of Africa and some habitats in the American and Asian tropics. At an average of 12 percent/year, meliponine colony mortality from predators in this study was generally higher than those reported for American and Asian tropics. The use of tools by humans and chimpanzees caused high rates of stingless bee nest mortality. Temporal resource partitioning and climatological factors influencing colony flight and foraging of stingless bees is discussed in chapter 5. Foragers of M. ferruginea and M. nebulata exited their nests in characteristically distinct foraging bouts suggesting the recruitment methods used may be direct leading or ‘piloting’. The number of individuals in a returning bout was less than that in an exiting bout suggesting recruits do not follow experienced foragers the whole distance to food source. Differences in pollen foraging by A. mellifera and stingless bees (M. bocandei and M. nebulata) were studied in chapter 6. Palynological results showed an overlap among the three bee species. A. mellifera the larger bee had the highest diversity while M. nebulata had the lowest. The recruitment technique to food sources is implicated to have been one of the factors accounting for the differences in pollen foraging behaviour. Foragers of M. nebulata flew out in distinct bouts which probably led to the low pollen diversity. Chapter 7 discusses factors influencing sugar concentration of collected nectar. Two stingless bee species (H. gribodoi and M. ferruginea) were used to show co-existence among the two genera. The smaller bee (H. gribodoi) collected nectar of higher sugar concentration. Factors that influenced sugar concentration of collected nectar included botanic origin of the nectar, bee species, bee colonies, month of year, time of day and the local environment. In Chapter 8, a study on seasonal floral resource utilisation and pollen collection by A. m. scutellata was undertaken. Results showed that the flowering time of bee plants varied with the different seasons of the year. Most plants bloomed during the rainy season while agricultural crops flowering depended on sowing date. There was more brood-rearing during the rainy season, when flowers were in bloom