Between New Year and Easter, the question which I am most frequently asked is : “Do Bees Hibernate?”
The short answer is that they form a cluster, a gently dynamic, oval mass in the middle of the brood box, dropping their metabolic rate by a couple of notches. But the full answer to the question is a little more complicated than that.
It all depends on what you mean by “hibernate”. Insects are cold-blooded and bees are no different. However, honeybees fall into the small minority of insects which can generate their own heat, like mammals, through muscular exertion (human beings do this by shivering, for example). So let’s see where we can check the box on bees having a regular “hibernation“: seasonal cycle, Yes, metabolism slows down, Yes, own thermoregulation, Yes.
But if by “hibernation” you mean a state of suspended animation, like a bear or a bat, or a comatose Rip Van Winkle interlude, snoozing unrelentingly thorough 3 months of oblivion, then “No”, bees don’t hibernate like that.
As winter takes hold, bees form their cluster. Composed of some 10,000+ winter bees (late-born in the previous Autumn and physiologically endowed with a body able to store fat), it expands and contracts, according to the exterior temperature. Food consumption drops as long as the bees remain in this torpid state. But in warm spells, the cluster will relax, with some bees even leaving the hive to make “voiding flights” and dedicated mortuary bees removing dead bees from the hive.
But the cluster will huddle protectively tight to conserve heat as the temperature drops. The grim fact is that, if the thorax of a bee (where the wings are located, between the bees’ head and the abdomen) falls to a temperature a few degree below 10C, a bee will fall into a “chill coma” which renders it rigid, motionless and unable to vibrate its wing muscles to create the heat required for its cold-blooded body to stay alive.
Honeybees overwinter as a reduced colony, a living, slow-motion family unit with the Queen at the centre, unlike wasps or most other bees, where fertile queens shelter alone. This behaviour illustrates why scientists have described colonies of bees as “superorganisms” in which each individual bee is only a component part of the greater whole. The concept of a colony of bees as a single social civilisation is key to my beekeeping.
Let’s take a closer look at the cluster: the outer mantle of bees is like a string vest, insulating the soft body of this concentration of bees. These wrapper bees will eventually rotate their positions with warmer bees, bubbling up from the heated community of the cluster. In temperature terms, this outside layer will be at around 10-15C, with the main body of bees at 22-24C and new brood at the centre requiring a temperature of 33-35C. That means that the part of the hive where the bees cluster will be almost as warm as a centrally-heated home in winter, the main mass of bees overwinter at the same temperature as a balmy summer’s day, while the brood area as hot as a Caribbean holiday – even when the weather is freezing outside !
So my answer to the question “”Do Bees Hibernate?” is an unsatisfactory one. They sort of do, but they kind of don’t. But I was excited to stumble across one insight as I was thinking this article through.
The cluster is hard to see, buried deep inside a winter beehive and divided by brood frames, so my challenge was: how can I help people visualize a cluster? Then it came to me: take a look at the photo at the top of the page.
Here you can actually see the egg-shaped formation and mantle of outer bees typical of a cluster. But this is a swarm of bees, settled on a branch.
It really made my day when I realised that a swarm of bees is just a naked cluster !