In the absence of human intervention, the honeybee (Apis mellifera L.) usually constructs its nest in a tree within a tall, narrow, thick walled cavity high above the ground (the enclosure), however most research and apiculture is conducted in the thin walled, squat wooden enclosures we know as hives. This experimental research, using various hives and thermal models of trees, has found that the heat transfer rate is approximately 4 to 7 times greater in the hives in common use, compared to a typical tree enclosure in winter configuration. This gives a colony mass, lumped nest thermal conductance ratio (MCR) of less than 0.8 for wooden hives and greater than 5 kgW-1K for tree enclosures. This result for tree enclosures implies: higher levels of humidity in the nest, increased survival of smaller colonies and lower Varroa destructor breeding success. Many honeybee behaviours previously thought to be intrinsic may only be a coping mechanism for human intervention; for example, at an MCR of above 2 kgW-1K, clustering in a tree enclosure may be an optional, rare, heat conservation behaviour for established colonies, rather than the compulsory, frequent, lifesaving behaviour it is in the hives in common use. The implied improved survival in hives with thermal properties of tree nests may help to solve some of the problems currently facing honeybees in apiculture.
Keywords: Apis mellifera, tree nest, varroa, heat transfer, clustering
Description:
Abstract
In the absence of human intervention, the honeybee (Apis mellifera L.) usually constructs its nest in a tree within a tall, narrow, thick walled cavity high above the ground (the enclosure), however most research and apiculture is conducted in the thin walled, squat wooden enclosures we know as hives. This experimental research, using various hives and thermal models of trees, has found that the heat transfer rate is approximately 4 to 7 times greater in the hives in common use, compared to a typical tree enclosure in winter configuration. This gives a colony mass, lumped nest thermal conductance ratio (MCR) of less than 0.8 for wooden hives and greater than 5 kgW-1K for tree enclosures. This result for tree enclosures implies: higher levels of humidity in the nest, increased survival of smaller colonies and lower Varroa destructor breeding success. Many honeybee behaviours previously thought to be intrinsic may only be a coping mechanism for human intervention; for example, at an MCR of above 2 kgW-1K, clustering in a tree enclosure may be an optional, rare, heat conservation behaviour for established colonies, rather than the compulsory, frequent, lifesaving behaviour it is in the hives in common use. The implied improved survival in hives with thermal properties of tree nests may help to solve some of the problems currently facing honeybees in apiculture.
Keywords: Apis mellifera, tree nest, varroa, heat transfer, clustering