The relative success of Africanized and European honey-bees over a range of life-zones in Costa Rica

The reproductive success and biology of Africanized and European Apis mellifera were compared for a year over three life-zones from 900-2800m. Determinations of colony success and comparative biology included survivorship during the rainy season, causes of colony mortality, frequency of swarming, absconding, seasonal patterns of weight gain, brood-rearing (worker and drone), and nectar and pollen storage. More European than Africanized colonies died from gradual weakening, and only Africanized colonies absconded. Colony deaths and absconding occurred with approximately equal frequency over all elevations during the year. Almost three times as many Africanized as European colonies swarmed over the year. Most swarms occurred in the dry season at the lowest apiary, but both bee types issued swarms at the highest elevation. Africanized colonies weighed significantly more and maintained significantly larger worker brood areas than European colonies across all elevations for most months of the year, except at 2800 m from March-June. Africanized colonies reared more drones than European colonies, except during the dry season at the highest elevation. The most pronounced differences between the bee types were observed in the lowlands, which accounts for the rapid population growth and range expansion of Africanized bees, and their displacement of European bees in these areas. -from Authors