Honey Bees in Winter – Do Bees Hibernate?

Each winter, I marvel at the astonishing ability of our beloved honeybees to withstand the weather. To survive, and to thrive the coming season as if the winter had been but a doddle. These tiny creatures, so busy in the summer months, seemingly disappear as the days grow shorter and the chill sets in. Yet, they are not gone. Far from it. They are in their hives, weathering the winter storms, surviving, and preparing to emerge in the spring as if the harsh winter was nothing more than a minor inconvenience. But what really happens inside a beehive in winter? Do bees hibernate? Do they sleep? Let’s look into the hive and uncover the secrets of their winter survival.

Winter Bees vs Summer Bees

The first thing that happens in a beehive at the onset of winter is that the worker bees start to age more slowly. Interestingly, the lifespan of a worker bee varies significantly depending on the season. During the active summer months, worker bees live for approximately 6 weeks. Their lives are filled with ceaseless activity, including cleaning, feeding larvae, making beeswax, guarding the hive, and foraging for nectar and pollen. However, in the winter, worker bees, also known as “winter bees”, can live for up to 4 to 6 months. This extended lifespan is crucial for the survival of the colony through the cold months.

The key difference between winter bees and summer bees lies in their physiological changes. Winter bees develop what is called a “fat body”, an internal food storage that is enlarged in winter bees. This change occurs when bees do not engage in brood-rearing and producing brood food. These winter bees are essential for the colony’s survival as they rear the first bees of the next spring.

Break in Brood Rearing

The second thing that happens in a beehive in winter is that the queen slows down her egg laying, and it eventually stops. In Ireland, we usually find that we have a brood-less period at some stage in December, and that brood rearing starts again in January. This is quite curious as January is often colder than December. It has been suggested that day length, or whether the days are getting shorter or longer, may be more important to the bees that the ambient temperature. Conversely, you can also see bees (and nature) reacting to day-length at the other end of the year, where the honey flow usually start around summer solstice, when the days are starting to get shorter.

Regardless of the reason for the timing of the winter brood break, the break is very important for the bees as it also provides a break in the breeding cycle of the parasitic Varroa mite. This is because Varroa need honeybee brood in order to breed and multiply. This is also why many beekeepers perform mite treatment in the middle of winter to get rid of the phoretic mites (mites that cling on or attach themselves to adult bees) so that when brood rearing begins in the hive, the varroa load has lessened significantly.

Clustering and Temperature Regulation

The third thing that happens in a beehive in winter is that, as temperatures drop, bees begin to form a winter cluster. They do this in order to reduce heat loss and maintain a survivable temperature. The cluster, which is ball-shaped and formed with the frames and comb running through it, starts to form when the outside air temperature falls to about 14°C (57°F). The bees in the cluster generate heat by eating and metabolizing honey and by shivering or vibrating their flight muscles.

The inner temperature of the cluster varies depending on whether there is brood present. If brood-less, the temperature is about 20°C (68°F). If there is brood present, the temperature rises to the mid-thirties Celsius. As the outside temperature drops further, the cluster tightens to conserve heat and loosens as temperatures rise.

It is not unusual to see bees out flying on warm, calm and sunny winter days. During such days bees in a strong colony may break from the cluster and leave the hive. They do this primarily for two reasons: To gather fresh pollen and to defecate. Pollen is important once the queen has started laying again, as this is transformed into brood food which is fed to the developing larvae. Without pollen, there would be no new bees. This is why it is so important to plant shrubs and plans that flower during winter such as mahonia, snowdrops, crocus, hellebores, and viburnum to name a few. The second reason bees leave the hive in winter is to poo! Bees are very clean creatures and the inside of the hive is kept immaculate. After all, this is where they store their food and rear their young, so it wouldn’t do to have excrement mixed up with that. Hence, bees that need to go for number two do so outside the hive….

Role of Honey in Winter Survival

Honey plays a crucial role in the survival of honeybees during winter. Because, as we have discovered, honeybees do NOT hibernate they need food supplies to ensure the survival of the colony, no matter how cold or long the winter is. This is in fact, the very reason why honeybees make honey in the first place: to make sure that the colony has what it takes to survive the winter as a whole.

The bees consume the stored honey to generate heat within the cluster. It’s essential for the survival of the colony that the food is close to the cluster, especially if the winter is cold and the colony is weak or have a small bee-mass. The food is often found immediately above the cluster, and the cluster can also move throughout the winter as they consume the honey stored in the hive. This proximity ensures that the heat rising from the cluster keeps the honey from crystallizing too quickly, staying soft for longer, and remaining usable by the bees with minimum effort.

Survival Strategy: Killing the Drones

Interestingly, honeybees have a somewhat ruthless survival strategy. As winter approaches, female worker bees evict or kill most, if not all, drone bees (males) from the hive. Since drones live primarily to mate with queens from other colonies, and the queen does not mate during winter, the drones become a needless drain on resources. By evicting or killing the drones, the hive conserves precious food resources for the worker bees and the queen, ensuring the colony’s survival through the winter.

Threats to Colony Survival

Despite their resilience and adaptability, honeybees face several threats during the winter months that can jeopardize the survival of the entire colony. Here are some of the main threats:

Lack of Food

Honeybees rely on their stored honey to survive the winter. If a colony does not have enough food stored, it can starve before spring arrives. This is why beekeepers sometimes provide supplemental feeding to their bees in late autumn or early winter. The main threat of starvation comes in a prolonged, cold spring, when the bees have used up the food stored for the winter.

Read more about feeding bees.

Dampness

Dampness in the hive can lead to a host of problems, including the chilling of bees and brood, and the growth of mould. Bees can usually tolerate cold well, but they struggle with damp conditions. Good hive ventilation is crucial to prevent dampness and condensation. To read more about condensation and ventilation, check out this blog: Beehive insulation, condensation and ventilation.

Varroa and Other Diseases

The Varroa mite is a significant threat to honeybees, and its effects can be particularly devastating in winter when the colony is already under stress. The mites weaken the bees and is a vector for diseases and viruses. Other diseases, such as American and European foulbrood or Nosema, can also pose a threat to overwintering colonies.

Pests

Pests such as rats and mice can pose a threat to honeybee colonies in winter. These rodents are attracted to the warmth of the hive and the food stores within. They can chew through the hive structure, causing damage and stress to the colony.

So, do bees hibernate?

So, do bees hibernate in the winter? Do they sleep? The answer is No! Our Ntive Irish Honey bees (Apis mellifera mellifera) survive the winter by living off the honey they’ve made and stored, and by huddling together in a cluster around the queen and her brood. They shiver, vibrate their wings, and generate heat within the hive to keep themselves warm, and they can freeze or starve to death if they run out of honey.

However, it’s worth noting that not all insects follow the same pattern. For instance, wasps and bumblebees do hibernate, but only the mated queens. For more information on the lifecycle and winter habits of both wasps and bumblebees, please refer to these blogs: Wasps and Bumblebees in Winter.

In conclusion, honeybees exhibit remarkable adaptability and resilience, employing sophisticated strategies to survive the harsh winter months. From physiological changes and temperature regulation to judicious resource management, these tiny creatures offer a fascinating study in survival and sustainability. After all, as my son like to say, they’ve been around since the time of the dinosaurs!

Hanna Bäckmo

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