Are man-made hives valid thermal surrogates for natural honey bee nests (Apismellifera)?

Honey bees preferentially occupy thick walled tall narrow tree cavities and attach their combs directly to the nest wall, leaving periodic gaps. However, academic research and beekeeping are conducted in squat, thin walled man made hives, with a continuous gap between the combs and the walls and roof. Utilising a computational fluid dynamics (CFD) model of thermoregulating bees in complete nests in trees and thin walled man made hives, with the average size of tree comb gaps determined from honey bee occupied synthetic tree nests, this research compared the metabolic energy impacts of comb gaps and vertical movement of the thermoregulated brood area. This shows their heat transfer regimes are disparate, including: bee space above combs increases heat loss by up to ∼70%; hives, compared to tree nests, require at least 150% the density of honey bees to arrest convection across the brood area. Tree cavities have a larger vertical freedom, a greater thermal resistance and can make dense clustering redundant. With the thermal environment being critical to honey bees, the magnitude and scope of these differences suggest that some hive based behavioural research needs extra validation to be considered non-anthropogenic, and some bee keeping practices are sub-optimal.

Honey bee (Apis mellifera) size determines colony heat transfer when brood covering or distributed.

Heat transfer is key to the survival of honey bee colonies (Apis mellifera L.) in the wide range of hot (e.g. sub-Saharan) and cool climates (e.g. maritime-temperate) in which they have evolved and adapted. Here, a validated computational fluid dynamics, conjugate heat transfer model was used to determine the heat transfer of honey bee colonies in simulated standard wooden hives, complete with combs and brood, for a broad range of honey bee sizes, from slender lowland African A.m. scutellata, to broader (larger diameter) Northern European A.m. mellifera, across the whole range of brood covering honey bee densities, as well as when evenly distributed throughout the hive. It shows that under cooling stress, brood covering, broad subspecies need less than a third of the number of bees per unit of brood area for thermal insulation compared to slender subspecies. Also, when distributed evenly around the nest, broad subspecies lose less brood heat than when brood covering. These simulations demonstrate that honey bee girth has climate-based evolutionary advantages directly for the colony as well as via the survival of the individual. In addition, it shows that non-clustering behavioural patterns of passive honey bees can make significant, subspecies distinctive changes to nest heat loss and therefore honey production and climate change survival.