Bee survival in winter varies significantly by species. Some colonies endure collectively, while others rely on a single individual or the next generation.
Honey Bee Colony Survival
Honey bee colonies demonstrate a sophisticated social strategy to survive winter. As temperatures drop, worker bees form a compact “winter cluster” inside their hive. They generate heat by rapidly vibrating their flight muscles, maintaining a core temperature of around 91 to 97 degrees Fahrenheit. This keeps the queen bee warm at the cluster’s center, essential for colony continuity.
The cluster constantly adjusts its shape, expanding and contracting to regulate temperature and allow bees to rotate positions, ensuring no individual becomes too cold. Honey bees do not hibernate; instead, they remain active at a reduced rate, consuming stored honey for energy. These colonies typically require 50 to 60 pounds of honey reserves to sustain themselves. Winter bees, born in the fall, have a longer lifespan and higher fat content, enabling them to endure the cold and care for the queen and future brood. Male drone bees are typically evicted from the hive as winter approaches to conserve vital resources.
Bumble Bee Winter Strategies
Bumble bee colonies employ a fundamentally different approach to winter survival. Most bumble bee colonies are annual; the majority of the colony—including all workers, males, and the old queen—perish with the onset of cold weather. Only new, fertilized queens survive. Mated in late summer or fall, these queens consume ample nectar and pollen to build fat reserves.
They then seek sheltered locations called hibernacula for their solitary overwintering period. These spots include leaf litter, wood piles, or small burrows 5 to 15 centimeters deep in the ground, often on north-facing slopes to prevent premature warming. The queen enters a state of dormancy known as diapause, where her metabolism significantly slows. During this time, she produces a natural antifreeze, such as glycerol, to prevent freezing. When spring arrives, these queens emerge to establish new colonies.
Solitary Bee Overwintering
Solitary bees, which constitute the majority of bee species, have diverse overwintering strategies focusing on offspring survival rather than adult bees. Adult solitary bees complete their life cycles and die before winter begins. Their survival hinges on the next generation, which spends the winter in a dormant state within protected nests.
Female solitary bees prepare these nests by laying eggs in individual cells, providing each with a supply of “bee bread” made from pollen and nectar. The developing bees remain in these sealed cells as larvae or pupae throughout the winter, protected. Nests can be found in ground tunnels, hollow plant stems, or pre-existing cavities in wood. For example, mason bees typically overwinter as adults inside their cocoons, while leafcutter bees overwinter as dormant pre-pupal stages.
Supporting Bee Survival in Winter
Individuals can take several actions to help bees navigate the winter months. Delaying garden cleanup until spring provides crucial overwintering habitats. Leaving fallen leaves undisturbed offers shelter for hibernating bumble bee queens and insulation for ground-nesting solitary bees. Hollow plant stems and dead annuals or perennials can also provide refuge for various bee species.
Planting a variety of late-blooming and early-blooming flowers ensures that bees have access to vital nectar and pollen sources when other forage is scarce. Examples of beneficial early spring flowers include crocuses, primroses, hellebores, and snowdrops, which provide sustenance for emerging queens and active honey bee colonies. Minimizing or avoiding pesticide use is important, as these chemicals can disrupt bee survival and reproduction, even at low concentrations or during periods of dormancy. Pesticides can weaken bees and make them more susceptible to cold or other stressors.