Bees, like many creatures, face unique challenges when winter arrives. Do they go dormant? The answer is not a simple yes or no, as various bee species employ distinct strategies to endure the winter. Some bees enter a state of reduced activity, while others maintain a complex social structure and remain active within their nests.
Honey Bee Winter Survival
Honey bees do not hibernate; instead, the entire colony works collectively to survive winter. When temperatures fall below approximately 50-57 degrees Fahrenheit (10-14°C), worker bees form a compact “winter cluster” inside their hive, huddling around the queen and any developing brood. This clustering behavior allows them to generate and conserve heat by rapidly vibrating their flight muscles. Bees on the outer layer are tightly packed, forming an insulating mantle, while those in the core are more loosely arranged.
The cluster’s core maintains a warm temperature, typically 90-97 degrees Fahrenheit (32-36°C) when brood is present, and 70-85 degrees Fahrenheit (21-29°C) without brood. Bees on the exterior keep their heads pointed inward, continuously rotating positions with warmer bees from the inside to ensure no individual bee becomes too cold. Throughout winter, the colony relies on stored honey reserves as their primary fuel source, consuming it to power muscle vibrations.
As winter progresses, worker bees expel male drones from the hive, as they are not needed for reproduction and consume resources. The queen reduces or stops laying eggs in early winter, conserving the hive’s limited food supply, though she resumes laying in late winter to prepare for spring. On warmer winter days, bees may take brief “cleansing flights” outside the hive to excrete waste, as they avoid defecating inside the hive.
Winter Survival for Other Bee Species
Other bee species exhibit different winter survival mechanisms, often involving a state closer to true dormancy. Bumble bees have an annual life cycle where the entire colony perishes with the onset of cold weather. Only newly mated queen bumble bees survive the winter.
These queens seek secluded, sheltered locations, often burrowing underground, under leaf litter, or in abandoned rodent holes. They enter a state of diapause, a period of arrested development and reduced metabolic activity, conserving energy on stored fat reserves. They remain inactive until spring, emerging to establish new colonies.
Solitary bees, a diverse group including mason bees and leafcutter bees, also have unique overwintering strategies. Unlike social bees, solitary bees do not form colonies; each female constructs her own nest and lays eggs. Most solitary bees overwinter as larvae or pupae within their protective cocoons inside nesting cavities, such as hollow stems, wood tunnels, or underground burrows.
These developing bees enter diapause, pausing growth until spring. Mason bees can overwinter as fully formed adults inside their cocoons, relying on stored fat until emerging in early spring. Their cocoons are often protected within bee hotels or natural cavities, protecting them from harsh winter conditions.
Factors Affecting Winter Resilience
Several factors influence bee winter survival, regardless of their strategy. Environmental conditions play a role, with extreme temperature fluctuations and prolonged cold negatively impacting bee colonies. Access to sheltered nesting sites and protection from strong winds are important for maintaining stable temperatures within hives or individual overwintering spots.
The availability of sufficient food stores is another factor. Honey bees require ample honey reserves to fuel their winter clustering, requiring a substantial amount gathered during warmer seasons. For bumble bee queens and solitary bee larvae/pupae, building adequate fat reserves before entering diapause is important for survival until spring. Summer weather conditions, such as prolonged rain, can diminish foraging time, leading to reduced food storage for winter.
The overall health of a bee colony or individual bee entering winter impacts survival. Diseases and parasites, particularly Varroa mites in honey bee colonies, can weaken bees. Varroa mites feed on bee fat bodies, compromising health and reducing the lifespan of “winter bees” adapted for longer survival. A healthy, productive queen is also important for honey bee colony survival, as she lays the “winter bees” that ensure the colony’s continuity.
Human activities also influence bee winter resilience. Habitat loss reduces natural foraging grounds and nesting sites, limiting resources bees can gather for winter. Pesticide use can weaken bees, making them more susceptible to disease and less able to withstand cold temperatures. Beekeepers can support honey bee winter survival through practices like ensuring adequate food stores, providing insulation for hives, and implementing integrated pest management strategies to control Varroa mites.