When cold weather arrives, many people wonder what happens to bees, often assuming these busy pollinators simply disappear. However, bees employ remarkable and diverse strategies to survive the winter months. Their methods vary significantly depending on the bee species. Instead of vanishing, bees adapt their behavior and physiology to endure the cold and ensure their survival until warmer temperatures return.
Honey Bee Winter Behavior
Honey bees do not migrate or enter a state of true hibernation; instead, they remain active inside their hives throughout winter. When temperatures drop below approximately 50-57°F (10-14°C), honey bees form a tight “winter cluster” around their queen and any developing young.
This cluster generates and conserves heat to maintain a core temperature of about 93-97°F (34-36°C), especially if brood is present. Bees on the inside of the cluster generate warmth by rapidly vibrating their flight muscles without moving their wings, much like shivering.
The bees continuously rotate positions within the cluster, allowing individuals from the cooler, outer layer to move towards the warmer core. This rotation ensures that no single bee becomes too cold. Their primary fuel source for this heat generation is stored honey, which they consume throughout the winter.
A healthy colony needs a substantial amount, often around 80-100 pounds, of honey to sustain itself. On warmer winter days, when temperatures rise above approximately 50-55°F (10-13°C), honey bees may briefly leave the hive for “cleansing flights.” During these flights, bees defecate outside the hive to maintain cleanliness within their living space. This behavior is crucial for preventing the buildup of waste and potential diseases inside the hive.
Bumblebee Winter Strategy
Unlike honey bees, most bumblebee colonies are annual; the worker bees, male bees, and the old queen all perish as winter approaches. The survival of the species relies solely on new, fertilized queens.
These new queens find sheltered locations to spend the winter alone, often burrowing a few inches underground in soft soil, under leaf litter, or within rotting logs. Once settled, the queen enters a state of diapause, a period of arrested development and reduced metabolic activity.
Her body temperature and metabolic rate significantly decrease, allowing her to conserve energy and survive on stored fat reserves. This dormant state protects her from freezing temperatures and lack of food sources. When spring arrives and temperatures become consistently warmer, the queen emerges from her overwintering site to begin foraging, establish a new nest, and lay eggs to start a new colony.
Solitary Bee Overwintering
Solitary bees, which make up the majority of bee species, have diverse overwintering strategies as they do not live in colonies. Most solitary bees survive the winter as larvae or pupae within individual cells of their natal nests.
These nests are typically located in various sheltered spots, such as hollow plant stems, tunnels in wood, burrows in the ground, or specialized mud cells. The young bees remain in a state of suspended development, or diapause, throughout the cold months.
For example, mason bees often overwinter as fully formed adults inside their cocoons, ready to emerge in spring when temperatures reach around 55°F (13°C). Leafcutter bees, conversely, typically spend winter as dormant, mature larvae within their leaf-lined cells. They complete their development into adults when temperatures consistently reach approximately 70-75°F (21-24°C) in late spring or early summer. This overwintering in protected natal nests allows solitary bee offspring to survive until conditions are favorable for their emergence as adults.