Hibernation of bumblebee queens
What you will learn here
- The hibernation of queens, which begins in the summer, is a part of bumblebee life that remains completely shrouded in mystery to most people.
- You will see details of bumblebee wintering.
- We will describe the reasons and methods of bumblebee and bumblebee hibernation
- We present the findings of Jaromír Čížek, obtained through many years of breeding bumblebees and observing them in the wild.
- We have recently updated the page with interesting photos and videos
- Information about this life stage of the bumblebee is a unique part of our bumblebee encyclopedia
- What to do if you find a hibernating bumblebee mother
Last updated: 21/1/2024
! WE ASK YOU VERY MUCH – DO NOT DISTURB THE MOTHER BEE IN THEIR WINTERING AREAS AND PROTECT THESE PLACES!
Contents:
The origin and reasons for bumblebee hibernation
Hibernation – a place to hibernate
Why does the queen bumblebee not freeze or starve in winter?
Species differences in hibernation
Options for determining the species of a hibernating bumblebee by finding a hibernation site
Danger lurks in the ground
What to do if you find a hibernating queen in the ground
Interesting videos
Wintering female bumblebee (Bombus rupestris)
Photo: J. Čížek
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The origin and reasons for bumblebee hibernation.
Summer is a very active time for us, mostly a time of recreation and sports. However, the fertilized queens of many bumblebee species do not share our rhythm and have already wintered or are currently preparing to winter.
But why in the summer?
Winter is not far away and there are more than enough warm days. Although the meadows are still blooming, the food supply is now smaller than in the spring months and there are even more insects interested. The lack of food forces wasps and bees, but even bumblebees, to rob supplies in other people's nests.
The food supply is decisive for the life cycle of bumblebees , with optimal environmental properties coming in second place.
The state of hibernation, in which bumblebee mothers age more slowly, ensures their good condition for the following season.
But it is not only about food. The mother, hidden from the world, also protects herself and her future offspring. Her main task is to establish and raise new sexual individuals in the new season. Therefore, most mothers hide underground and wait there for spring.
So it's time to wait for the next food optimum in the next season, i.e. to hibernate .
There are a few exceptions, where some queens do not hibernate under suitable conditions and start a new generation. These are mainly early-breeding species, such as the garden bumblebee (Bombus hortorum). These queens take the risk and find a place to nest. That is why you can see such species looking for a place to nest and even meet queens of their species at the end of the season. But that requires a lot of luck and patience in observation.
Let's now take a look at this important part of bumblebee life.
Mother bumblebee in spring – garden bumblebee (B.hortorum) – Photo Flićker
Hibernacle – a place to hibernate
After leaving the hive, bumblebees, as well as their future queens, set out to find a suitable place to hibernate . They need a place where they can burrow underground will not flood wintering area in winter/spring .
That's why they often prefer dry forest edges . There is plenty of dry pine needles as an insulating layer and clay underneath, in which they can dig a passage underground.
If they find such a place, they start digging a tunnel underground . They reach a maximum depth of about 10 cm. Each species prefers a different depth , as we will learn later in the text.
At the end of the corridor, they create a small cavity . It is just large enough for the queens to fit in. They then close the corridor and freeze in the cavity. They slow down their life processes (circulation of fluids, breathing and heart rate) to a minimum and hibernate. Hibernation is long and lasts several months , so they have to strictly conserve energy.
Bumblebees, as well as wasps, do not have enough energy to wake up repeatedly . This is always energy-intensive and, especially after waking up at an inappropriate time, they will not find a source of energy. Therefore, they need to find a suitable place and, with luck, wait there until the spring of the next year. Therefore, they prefer a place in the shade , even on the north side of the forest/growth. On the sunny side, the spring sun would wake them up prematurely. Such mothers are doomed - without a constant source of food, they will exhaust themselves and will not have the energy for another safe sleep...
If they wake up at the right time, they have a chance to find abundant spring flowers and win the competition. That's why early bumblebee species are hidden just below the surface , and later species, like the bumblebees, are hidden deeper. The bumblebees also wait until their hosts' mothers have built a large enough nest, and then they wait.
global warming and large temperature fluctuations adversely affect this strategy . As well as a warm winter, when bumblebees hibernate "shallow" and their energy consumption is higher than it should.
Interesting fact
- Bumblebee keepers have noticed that young queens sometimes return to their natal hive before winter. We believe that these are mothers going to sleep. If they need a plentiful source of energy when preparing a hibernacula or when searching for it, they look for it in their natal place and use the reserves there
- In the laboratory, thanks to stable temperatures, it is possible to keep bumblebee queens (some species) in hibernation much longer than winter lasts in nature, then wake most of them up and stimulate them to establish a nest
- The bumblebee queens are accompanied to the nest by the nymphs of the common bumblebee beetle (Parasitus fucroum). However, they do not harm them, as they need to get to the nest with her, which she will build in the spring. Even there, they will be mostly useful – feeding on the remains and waste in the nest
A mother bumblebee is looking for a place to hibernate.
Photo: Internet
Hibernating mother bumblebee
Photo: Bumblebee Conservation Trust
Mother bumblebee in hibernation
Photo: Jelly Fungus
Mother bumblebee in hibernaculum
Photo: Internet
Savenka beetle (Parasitus fucorum)
Photo: Biolib.cz
Why doesn't the queen bumblebee freeze or starve to death in winter?
As we already know, bumblebee queens, as well as bumblebees, bury themselves only a few centimeters into the ground .
However, at this depth they are in danger of death, because the ground freezes easily at such a depth. So how is it possible for a small creature to survive there?
Mother Nature has endowed bumblebees with a special ability. , substances gradually leach into their . Just as we humans have to add additives to the cooling system of our cars for the same purpose. So even though they are exposed to the cold for a long time, they can handle the winter. Even a cold one better than a warm one with temperature fluctuations.
During hibernation, queens do not eat. They get their energy from the fat body in their bodies . They created this in the nest when they fed there after birth. At that time, they devoured honey and pollen reserves. That is why mothers are born at a time when there are the largest number of workers in the nest and they will provide enough food. Young queens can literally "deplete" the reserves and often accelerate the demise of the weaker nest.
The saying “those who are thin – will be cold” also applies to bumblebees. In practice, this means that without a sufficiently large fat body, i.e. energy reserves, the young queen will not be able to survive hibernation and will die during it . It is a matter of a few grams of mass that gives her a chance to survive. A little less weight is enough and she has no chance.
During hibernation, approximately 80% of the energy stored in the fat body is consumed , mainly certain types of substances.
Weight is therefore essential . The robustness of the queens' bodies is necessary for all subsequent stages of their lives, including storing the males' sperm after they have been fertilized - they will only use it in the spring of the following year.
Another factor that is not fully described is the action of hormones and the processes after mating . A young queen that does not mate does not follow the instinct in feeding and then hibernation. You can also find such individuals in the nest. They are "aunts" and behave like large workers. They carry pollen and nectar, but as spinsters they do not live to see spring.
Overall health and fitness are therefore crucial. Damaged and otherwise handicapped mothers have no chance. But even so, it is not possible without a dose of luck .
From a human perspective, it may be cruel, but natural selection is something that gives a species a chance to survive – through healthy and strong individuals. Here, strong and healthy queen mothers.
Look what it looks like in the hibernaculum . Well, it's not an idyll and warm socks won't solve it...
Interesting fact:
- The fat body of bumblebee queens and the processes that take place within it are the key to their longevity. Unlike males and workers, they live for practically one year. You can read more about this HERE
- The fat body of bumblebees is the subject of research "A relatively large reserve is probably saved for active departure from the hibernation and finding the first food source after winter. Queens must reckon with changeable spring weather and the possibility that they will have to fly far for food. After the nest is established, the fat reserve is already low, while glycogen is still used for the queen's flight and movement while raising the first workers". You can read more, for example HERE
- You can find more interesting information, far beyond the scope of our scope, HERE
Mother bumblebee in hibernaculum
Photo: Reddit
Bumblebee hibernation
Photo: BBC
Bumblebee hibernation
Photo: BBC
Bumblebee hibernation
Photo: BBC
Bumblebee hibernation
Photo: BBC
Some species of bumblebees have to overcome much worse conditions than ours. Frosts here drop below -20°C, and winter lasts for up to 9 months.
Suitable conditions (we hesitate to call it summer) last for several weeks. An example of this is Bombus lapponicus (Lapland bumblebee) in northern Sweden.
This species of bumblebee has therefore chosen a strategy where it usually does not raise workers, but the mother herself takes care of new sexual individuals - she simply cannot do it otherwise. This species of bumblebee is also now threatened by climate change and is fighting for survival.
Nature sometimes wakes up hibernating bumblebee queens early. This video was filmed in January and unfortunately for this mother bumblebee it meant the end…
The video was recorded by Jakub Černý and can be found HERE
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Species differences in wintering.
There is a relationship between the depth of buried females below the surface and the division of species into early and late.
We will illustrate this with the following examples. The very early ground bumblebee Bombus terrestris is buried only just below the surface (often only 10-20 mm). In contrast, the virgin bumblebee ( Bombus vestalis ) , which must wait for the ground bumblebee's host nest to develop and take over, can be 40 mm or deeper below the surface.
A female vestal bumblebee (Bombus vestalis) preparing its wintering site.
Photo: J. Čížek
Possibilities of determining the species of a wintering bumblebee based on the finding of a wintering site.
If we manage to find a hibernaculum in the forest, we can estimate what kind of individual is overwintering there based on the appearance and amount of excavated material. For the rock bumblebee B. lapidarius , a typical feature is an entrance groove that is not covered up. For the ground bumblebee B. terrestris, it is characteristic that the excavated material is only humus, without soil content.
In the case of the patchouli, on the other hand, the excavated material is mostly clay, without humus content. The attached photos show you what such a hibernaculum looks like and how it is created by its inhabitants.
Wintering grounds of the bumblebee (Bombus terrestris)
Photo: J. Čížek
Hibernation site (hibernaculum) of the rock bumblebee (Bombus lapidarius)
Photo: J. Čížek
A typical example of a hibernaculum of a bumblebee (Bombus terrestris)
Photo: J. Čížek
Wintering grounds of the rock bumblebee (Bombus lapidarius)
compare the differences between the wintering grounds of the ground bumblebee
Photo: J. Čížek
Wintering grounds protection
Now you know what such places look like. You also know very well that an early awakening means an early end for a sleeping queen. You also know what risks await sleeping queens.
If you manage to discover any bumblebee wintering grounds in nature, please
Be considerate of them and protect them.
You can mark the area around such places with pins and add a suitable information sign.
The bumblebees will then repay us with their presence in the following season. With luck, you will meet them in the spring, leaving their hibernacula and basking in the rays of the spring sun.
Wintering site of the vestal bumblebee (Bombus vestalis)
Photo: J. Čížek
Wintering site of the vestal bumblebee (Bombus vestalis)
Photo: J. Čížek
Danger lurks in the land
Hibernation of bumblebee queens is always a risk. They can be flooded , attacked by mold , found by an insectivore or dug up by another animal looking for food in those places. They can also be dug up by a person , or the queens may not dig themselves out in the spring, they may wake up prematurely , etc.
A number of other enemies lurk in the soil – such as the parasitic nematode Sphaerularia bombi .
The development of this nematode goes through several stages , primarily in the ground. Once a bumblebee is attacked, the nematodes take hold in its organs, later in the intestine . Here they go through several stages.
In the final stages, nematode eggs and eventually adults and females emerge from the bumblebee's gut. This final stage means death for the bumblebee.
These parasitic nematodes have also been shown to alter the behavior of the infected individuals , similar to other parasites. Therefore, infected queens repeatedly burrow and simultaneously spread nematode eggs into the soil .
Similarly, infected bumblebee queens, if they survive hibernation, do not build nests but only gather food. They can also be seen in places where they occur in bumblebee wintering grounds where this parasite occurs and apparently help with its reproduction.
A change in the behavior of a mother bumblebee in nature is very often a sign of an infestation by this parasite . It is quite possible that in the spring we may encounter a mother that is attacked and will not build a nest .
You can read more about the parasitic nematode Sphaerularia bombi HERE and also HERE
What to do if you find a hibernating mother in the ground
If you find hibernating bumblebee queens during fall/spring work, it's a problem, but give them a chance to survive!
We kindly ask you to leave hibernating mothers in the wild and never bring them home to warm up. Early awakening from hibernation would mean loss of energy and death from exhaustion.
So what to do?
- Ideally, leave them where you found them . Carefully cover their hibernaculum with the same material , or dry peat, or pine needles from undergrowth at the edge of the forest.
- Alternatively , let them hide carefully cover the area so that they can dig themselves out in the spring.
- If you can't leave them in the same place , find a place in the immediate vicinity that we describe on our website and carefully move . It should always be a dry place with material that the bumblebee queens can dig out , where it doesn't rain the sun doesn't shine if possible .
The depth and orientation to the cardinal points should be the same as where you found it. - If you don't know what to do , contact Čmeláky PLUS via Facebook, or write to rychlarota@cmelaciplus.cz
Interesting videos
In the following video, you can watch a mother bumblebee looking for a place to hibernate and hiding in her hibernaculum.
Source: George Pilkington www.nurturing-nature.co.uk and YouTube
Another video of a mother bumblebee in hibernation, here a rock bumblebee (Bombus lapidarius) by Gordon White. Filmed in July 2020 in Buckfast, Devon England in Dartmoor National Park.
The following video shows how a mother bumblebee can burrow into the ground. The video shows their ability to hide in various materials.
In this video you see a mother bumblebee behaving strangely. Apparently she has been attacked by the parasitic nematode Sphaerularia bombi and her fate is sealed.
This is indicated by the date when it tries to hibernate (May), repeated attempts to bury itself, but also frequent bowel movements = spreading of nematode eggs into the soil.
! WE ASK YOU VERY MUCH – DO NOT DISTURB THE MOTHER BEE IN THEIR WINTERING AREAS AND PROTECT THESE PLACES!