This is a very good question! As you may have noticed, there are no bees flying around during cold winter days. For one thing, there are no flowers. But what keeps the bees inside the hive during the cold season is, you guessed, the cold.
As soon as the outside temperature drops below 55ºF (about 12ºC), honey bees cannot fly anymore (well, they can, but only for short periods of time, after which they have to stop and cannot take off again unless they are warmed up).
How Do Bees Stay Warm Inside the Hive?
Hives provide some protection from wind and cold during winter, but they are not heated. During very cold days, the temperature inside a hive can easily drop below 55ºF, and even below freezing. How do bees inside manage to stay alive?
A thermal image of a bee cluster (in red) located in the lower portion of a hive during winter.
Honey bees do not hibernate like bumble bee queens or other insects. They have to maintain their body temperature higher than ambient temperature, and they have been designed with a very smart way to do that: they can uncouple, or disconnect the flight muscles from their wings and generate a lot of heat by shivering.
Shivering to generate heat in cold weather is something humans have in common with honey bees, except that bee are so good at it, we can’t even see it!
How efficiently are bees at generating heat by shivering?
Very efficiently! In fact, during the long cold winter months, while clustering together in the hive, this is what bees do most of the time. Imagine shivering and huddling together with a few thousand other people to stay warm! But for bees this is the way to make it through the winter. They take turns shivering, keeping the center of the cluster and any brood at about 94ºF. When they get tired or too cold, they move to the center of the cluster, and other bees start their shivering shift. Bees on the outside of the cluster have to maintain their body temperature above 41ºF, otherwise their muscles stop working, and they die.
When the outside temperature warms up above 55ºF, the bees sense it and take the opportunity to go for a cleansing flight. That is a fancy name for a bathroom trip. Yes, you are right! Honey bees do not go to the bathroom inside the hive during the winter. They can hold their poop in for weeks on end, until a warmer day comes around and gives them a chance to get out and relieve themselves. How are they able to hold things up for such a long time? Part of the answer has to do with the fact that adult bees eat mostly honey, so there isn’t much fiber to deal with… They are clean insects, not just smart, aren’t they?
Today, a lot of our bees were taking cleansing flights. But since the weather was unseasonably warm around noon, a lot of them took a chance and went looking for food. We didn’t think they would find any, but we were wrong! Quite a few returned with sizable loads of pollen.
Watch below a short clip of one such returning bee, with some pollen on her hind legs, trying to warm herself up after landing on the side of the hive. Notice how vigorously she is pumping her abdomen! What that does is it draws a lot of air through tiny openings on her thorax (the segment of a bee’s body where the wings are attached). The flight muscles are able to extract a lot of oxygen from this air, allowing the bee to shiver hard and generate a lot of heat to warm herself up. (Remember, bees are shivering so fast, you can’t see it). The air is then pushed out of the bee’s body (together with the carbon dioxide) through specialized tubes that take it all the way to small openings on the bee’s abdomen and then out into the environment.
Why Are Bees Flying Out During Winter?
There are a handful of reasons for bees to fly out during a warmer winter day. We’ve covered a couple above. Here is a more complete list:
- To relieve themselves.
- To look for pollen to feed their larvae. Sometimes they bring in water, too, though most of their winter water intake is supplied by honey and water condensation forming inside the hive. Most likely, they are also looking for nectar, but there is none available during winter.
- To drag out dead bees from the hive.
- To take orientation flights and learn their hive’s location (younger bees).
Watch Jayden explain it better than I can write:
There are a lot of other things to learn about what bees do during the winter, but I’ll stop here today. We’ll try to write a post soon about how to feed bees during winter when they risk running out of honey or when we want them to get a early start on food raising young bees in time for the spring flowers.
