The idea of bees “hibernating” through winter is a widespread notion, yet it doesn’t accurately describe the diverse ways these insects survive colder months. Bees employ a range of unique strategies tailored to their social structures and life cycles, allowing them to cope with cold temperatures and limited food availability. Understanding these methods reveals the adaptability of different bee species, ensuring their survival until warmer weather returns.
Honey Bees and Their Winter Survival
Honey bees (Apis mellifera) remain active within their hive throughout the winter months. They form a compact cluster inside the hive, with the queen bee kept warm at its core. Worker bees on the cluster’s outer layer shiver their flight muscles, generating heat to maintain a hive temperature typically between 68-95 degrees Fahrenheit (20-35 degrees Celsius) within the cluster’s core, even when outside temperatures are well below freezing.
This heat is fueled by consuming stored honey, their primary energy source when foraging is impossible. The amount of honey required depends on the cold’s severity and duration, but a healthy colony might consume 30-60 pounds over winter. Bees rotate positions within the cluster, moving from the cooler outer layer to the warmer interior, distributing warmth effectively across the entire group.
Activity levels are reduced compared to warmer months, with foraging ceasing entirely as temperatures drop and floral resources become scarce. The queen’s egg-laying also slows or stops completely during the coldest part of winter, conserving her energy and the colony’s resources until spring. This collective behavior is crucial for the colony’s survival.
How Other Bees Endure Winter
Beyond honey bees, other bee species employ distinct strategies to survive the winter, often involving different life stages. Bumble bees, for instance, do not maintain a perennial colony like honey bees. As autumn approaches, the entire bumble bee colony, including workers and males, perishes with the onset of cold weather. Only the newly mated queen survives.
This new queen, having stored fat reserves, finds a sheltered location—typically underground in loose soil, under leaf litter, or in rodent burrows—where she enters a state of diapause, a form of hibernation. She remains dormant throughout the winter, emerging in spring when temperatures rise and flowers become available. She then searches for a suitable nesting site to establish a new colony.
Solitary bees, such as mason bees and leafcutter bees, exhibit another overwintering strategy. They do not form colonies or have a queen. Instead, they spend the winter in their larval or pupal stages within protective cocoons inside their nesting cavities. These nests might be hollow plant stems, tunnels in wood, or specialized bee houses. They remain dormant, undergoing metamorphosis, until spring warmth triggers their emergence as adult bees, ready to forage and reproduce.
Factors Influencing Bee Winter Hardiness
Several factors influence a bee’s ability to survive the winter, regardless of its specific overwintering strategy. Adequate food stores are crucial. For honey bees, this means sufficient honey and pollen reserves within the hive to fuel their cluster and sustain them until spring. Similarly, hibernating bumble bee queens and overwintering solitary bee larvae rely on stored fat reserves to survive their dormant periods.
The quality of insulation and shelter also impacts survival. A well-insulated hive protects honey bee colonies from extreme cold and wind, minimizing heat loss and conserving energy. For solitary bees and bumble bee queens, suitable nesting sites or burrowing locations offer protection from freezing temperatures, predators, and harsh weather elements. Moisture control is another important factor, as dampness within a hive or nesting site can lead to mold growth, chilling, and increased susceptibility to diseases. Proper ventilation helps manage this moisture.
Pests and diseases can compromise a bee’s winter hardiness. For honey bees, infestations like Varroa mites weaken individual bees and entire colonies, making them less resilient to the stresses of winter. Similarly, pathogens can debilitate bees, reducing their ability to generate heat or survive dormancy. For social bees like honey bees, the size and overall health of the colony entering winter are important; larger, healthier populations have a better chance of maintaining cluster integrity and surviving cold temperatures.
How to Help Bees Through Winter
Supporting bees through the colder months involves several practical actions that can be implemented in gardens and green spaces. One effective method is to delay garden cleanup until late spring. Leaving plant stems, fallen leaves, and other garden debris provides shelter for overwintering solitary bees, who might reside in hollow stems, and for hibernating bumble bee queens seeking refuge beneath leaf litter.
Avoiding early spring tidying ensures that any bees still in their dormant stages are not prematurely disturbed or exposed to cold. Providing water sources, even in winter, can be beneficial on milder days when bees might emerge briefly. A shallow dish with pebbles or marbles can offer a safe landing spot for bees to drink without drowning.
Planting early and late-blooming flowers extends the availability of nectar and pollen. Species like hellebores, winter aconite, crocus, asters, and sedums provide early-season food, while others offer late-season sustenance for bees preparing for winter. Avoiding the use of pesticides, particularly broad-spectrum varieties, is also important. These chemicals can harm bees directly or indirectly, weakening their populations and reducing their ability to survive winter.