I've only loosely been following this conversation as well but I have finally read Mitchell's paper and his media article that started this thread. 

My thoughts - I think it's foolish to only consider heat in this discussion. Just because a drop in ambient temperature triggers cluster formation, we can't assume heat conservation is the sole driver of clustering. Clustering at around the temperatures at which flowers stop producing nectar could be an adaptive response to the need for water or resource conservation or lifespan extension through anoxia or hypercapnia. 

While I could perhaps entertain the idea that heat is not retained within the cluster in the way in which we have historically imagined, it's unscientific to conclude clustering is "a desperate struggle to crowd closer to the 'fire' or die," and that "clustering is a distress behaviour, rather than a benign reaction to falling temperatures" (from https://theconversation.com/honeybees-cluster-together-when-its-cold-but-weve-been-completely-wrong-about-why-218066). 

It's unscientific because the other possibilities for why honey bees display an apparently adaptive response to dropping temperatures have not been considered. For example, an alternative hypothesis could be that clustering has evolved as a resource conservation or lifespan extension response, not as a heat conservation response, and that ambient temperature is simply the trigger. As I understand him, Mitchell has simply leapt to a conclusion that if a cluster does not effectively retain heat, there is no adaptive response and it is therefore a "distress behaviour." In biologist-speak, I don't even understand how "distress behaviour" relates to a discussion of adaptive and maladaptive strategies for survival (perhaps he could clarify?). 

I hope my point is clear- when the environment becomes stressful, in this case, due to a drop in temperature and reduced resource availability and foraging ability, honey bees colonies have evolved to respond by clustering. Clustering changes a colony's CO2 output, and the oxygen, carbon dioxide, and humidity levels to which bees are exposed, all of which may affect lifespan. All of these factors are vastly understudied compared to the thermology of the wintering cluster. Any or all of these factors could be equally or more important in explaining the evolutionary significance of clustering behaviour. 

Tracey
Alberta, Canada

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