Honeybee cluster-not insulation but stressful heat sink

• Published in: Journal of the Royal Society interface Vol. 20; no. 208; p. 20230488
• Main Author: Mitchell, Derek
• Format: Journal Article
• Language: English
• Published: England 22.11.2023
• Subjects: Animals; Beekeeping; Bees; Body Temperature Regulation; Gravitation; Hot Temperature; Seasons; Apis mellifera; convection; Extended phenotype; climate; ethics; welfare
• ISSN: 1742-5662; 1742-5662
• DOI: 10.1098/rsif.2023.0488

Since the early twentieth century, the outer layer (mantle) of honeybees ( ) in the winter cluster has been said to insulate the cluster core. This has encouraged enforced clustering, by the beekeepers' dominant use of inadequately insulated hives and, in North America, refrigeration. This is often seen as a benign or even a necessary process, with beekeeping and academic research considering these conditions of extreme heat loss, compared with the honeybee's natural habitat, as natural and normal. By using porous material correlations, analysis of previous findings and a model of a cluster within a hive in a landscape that implements convection, conduction and radiation, we show that a honeybee colony increases in thermal conductivity, on transition from pre-cluster to dense mantle, by a factor of approximately 2, and insulation -value can decrease by more than 11. These results show that the mantle does not act like insulation and that clustering is not benign, but instead is an evolutionary behavioural reaction to an existential threat that results in increased cold and exertion stress. Thus the attitude to forced clustering, i.e. deliberately provoking a stressful survival behaviour, needs revision as avoidable forced stress upon animals may be regarded as cruel.