What do bees do in the winter?

In nature, organisms have different strategies to deal with the winter. Some migrate (e..g many species of swallows and the the monarch butterflies), some hibernate (e.g. bears – though not polar bears), some stay at home and turn the heating up (I’ll take the fifth on this one).

Honeybees are really interesting creatures in many different ways. One of the ways that fascinates me is that they are cold-blooded creatures – their body temperature changes with their surroundings – but inside their colony, in the hive, they maintain a fixed temperature, mostly for the brood (larvae and pupae), as these are really sensitive to cold. Bees warm the hive by repeatedly flexing their flying muscles and thus generating heat.

As winter approaches, the colony does a few different things in preparation:

  • Reduce the bees numbers to the required minimum. Too many bees require a lot of food, so the bare minimum is better. Around early to mid fall, the (female) worker bees also kick out all the (male) drones who are left to die outside.
  • Collect as much honey as possible, as a food source for the winter.
  • Properly seal the hive (to preserve heat energy). This is done using propolis, the main ingredient of which is tree resin the bees collect.
  • Toward the end of fall, the bees stop rearing brood. The queen stops laying eggs, such that the existing bees will need to take the hive through the winter, but the hive’s temperature can now be lowered without harming the vulnerable brood.

Once winter sets in, the bees are in true survival mode. When the temperature outside is below 50 degrees F (10 C), they cannot fly and are hive-bound. When it gets really cold, the bees form a tight cluster where they heat one another. In the middle of that cluster you can find the most precious bee in the hive – the queen. The colder it is, the tighter the cluster will be.

The bees gradually consume their honey through the winter, starting with the lower portions of the hive and making their way up until they reach the top, at which point they likely exhausted all their honey stores.

The hive is in a very fragile state during the winter: many things can go wrong. There’s a delicate balance between having too many bees and too few bees – too many means not enough food, too few means they can’t heat the hive. The bees go into the winter with certain assumptions, by which it was determined who many bees are needed. If then some disease hits and more bees die, all of a sudden the hive could find itself below its critical number of bees, and there would be very little the beekeeper can do (other than go back in time and try to treat for whatever disease the bees had, and not all of them have available treatments).

Another obvious issue is the food storage. When it’s super-cold, the bees cannot move their cluster. They’re clustered so closely and tightly that the cluster is unable to change its position in the hive. A long cold spell could cause a hive to starve to death, even if they have honey available, as they couldn’t move their cluster to where that honey is stored. Again, very little the beekeeper can do at this point.

Hives that made it through most of the winter and got all the way to March, will likely start rearing new brood to create the first foraging bees of spring time. The most common issues for colonies that made it all the way to March is starving due to depleted honey stores. Here an attentive beekeeper can supplement their honey with dry artificial feed (typically sugar-rich patties), or if the outside temperature is warm enough, feed them some sugar-syrup (we avoid feeding liquids when it’s too cold in order not to introduce excess moisture to the hive, as that attracts fungi).

So there’s your answer: what do bees do in the winter? They cluster together to keep each other warm. Not a bad idea for humans either. Stay warm!