Reduced parasite burden in feral honeybee colonies

Abstract

Bee parasites are the main threat to apiculture and since many parasite taxa can spill over from honeybees (Apis mellifera) to other bee species, honeybee disease management is important for pollinator conservation in general. It is unknown whether honeybees that escaped from apiaries (i.e. feral colonies) benefit from natural parasite‐reducing mechanisms like swarming or suffer from high parasite pressure due to the lack of medical treatment. In the latter case, they could function as parasite reservoirs and pose a risk to the health of managed honeybees (spillback) and wild bees (spillover). We compared the occurrence of 18 microparasites among managed (N = 74) and feral (N = 64) honeybee colony samples from four regions in Germany using qPCR. We distinguished five colony types representing differences in colony age and management histories, two variables potentially modulating parasite prevalence. Besides strong regional variation in parasite communities, parasite burden was consistently lower in feral than in managed colonies. The overall number of detected parasite taxa per colony was 15% lower and Trypanosomatidae, chronic bee paralysis virus, and deformed wing viruses A and B were less prevalent and abundant in feral colonies than in managed colonies. Parasite burden was lowest in newly founded feral colonies, intermediate in overwintered feral colonies and managed nucleus colonies, and highest in overwintered managed colonies and hived swarms. Our study confirms the hypothesis that the natural mode of colony reproduction and dispersal by swarming temporally reduces parasite pressure in honeybees. We conclude that feral colonies are unlikely to contribute significantly to the spread of bee diseases. There is no conflict between the conservation of wild‐living honeybees and the management of diseases in apiculture.

Monitoring free-living honeybee colonies in Germany: Insights into habitat preferences, survival rates, and Citizen Science reliability

“…Yet, our findings suggest that the density of freeliving colonies in Munich remains relatively low, at approximately 4% of the density of registered colonies in the city (see SM for more information). While the local densities of managed colonies require careful consideration, free-living colonies should not be considered problematic for urban pollinators nor for managed colonies from urban beekeepers (see Kohl et al, (2023a) for an investigation on the parasite loads of free-living colonies).…”

Optimal fissioning strategies of social insects in dependence of colony dynamics and nest founding probability

“…This does not exclude that under such conditions moving of the entire colony to a new nest-site might be a fitness enhancing strategy, e.g. because nests become increasingly infected with parasites over time (Kohl et al, 2023); the higher survivorship of large swarms compared to large remaining colonies suggests that this is the case in honey bees. This fact may also be the reason why old queens moves along with the swarm and leave the old nest to a daughter queen.…”