The question of whether bees die in the winter has a complex answer that depends entirely on the species of bee. While the image of a bee colony perishing in the cold is a common misconception, many social bee colonies, particularly honey bees, have developed a remarkable strategy to ensure the unit survives the deepest winter months. For most other bee species, however, the entire colony, or nearly all of its members, do indeed die off, leaving only a few individuals or their offspring to endure the cold until spring.
The Honey Bee Strategy: Winter Clustering
Honey bee colonies survive the cold by forming a dense, self-regulating structure known as the winter cluster. This behavior is not hibernation; the bees remain active and maintain a stable temperature by consuming their stored honey reserves. When the temperature inside the hive drops to around 57°F, the bees pull together into a sphere or elliptical shape that minimizes surface area to conserve heat.
The cluster is composed of two distinct parts: a dense, insulating outer mantle and a more loosely packed inner core. Bees in the core actively generate heat through “shivering,” vibrating their flight muscles without moving their wings, which can raise the core temperature to between 70°F and 95°F, even when the ambient temperature is well below freezing. The outer mantle acts like a living blanket, with the bees on the periphery packing tightly together to prevent heat loss. Bees constantly rotate between the cold outer layer and the warm interior to prevent any individual from freezing. As they consume honey, the cluster slowly moves across the wax comb to reach new stores of food.
Survival Tactics of Solitary and Bumble Bees
Most non-honey bee species, including bumble bees and the vast majority of solitary bees, employ completely different strategies, which typically involve the death of the adult colony. Bumble bee colonies are annual rather than perennial, and they die off completely in the late fall. Only the newly mated queen survives the winter, having stored enough fat reserves to enter a state of dormancy known as diapause.
The solitary queen burrows a few inches underground into a protected spot like soft soil, leaf litter, or under rocks. Her body temperature and metabolism drop significantly during this time, allowing her to conserve energy and survive on her fat reserves until spring.
Solitary bees, such as mason bees and leafcutter bees, do not survive the winter as adults. Instead, the female lays her eggs in individual cells within a nesting structure, provisioning each cell with a ball of pollen and nectar before sealing it. The offspring develop into a larva and remain inside a protective cocoon. This dormant, protected stage ensures that a new generation emerges only when the weather warms and flowers begin to bloom in the spring.
Who Survives and Who Doesn’t?
Within the honey bee colony structure, there are specific fates for different members as winter approaches. The female worker bees prepare for winter by producing a distinct generation called “winter bees” in the fall. These winter bees are physiologically different from their summer counterparts, possessing enlarged fat bodies that store high levels of protein and lipids. This physiological adaptation gives them a greatly extended lifespan of four to six months, compared to the five to six weeks of a summer worker.
The male drones are expelled from the hive once the mating season ends. Drones do not forage or contribute to the winter cluster’s heat generation, making them a drain on the precious honey stores. Worker bees stop feeding them and forcefully remove them from the hive, where they quickly perish in the cold. Meanwhile, the queen is protected at the very center of the cluster, relying on the heat generated by the specialized worker bees for her survival.
The Primary Causes of Colony Loss
While cold temperatures are a challenge, most managed honey bee colony deaths are not caused by the cold itself, but by a failure in preparation or external threats.
Starvation
The most common cause of colony loss is starvation, which occurs when the colony runs out of honey stores before spring arrives. A colony in a northern climate requires 60 to 90 pounds of honey to fuel the heat-generating cluster throughout the winter.
Pests and Moisture
A major threat to colony health is the parasitic Varroa destructor mite, which feeds on the bees and transmits debilitating viruses. Mite infestations weaken the winter bees, reducing their fat body reserves and shortening their lifespan. Furthermore, moisture and poor ventilation can lead to a buildup of condensation inside the hive, which drips onto the cluster and causes the bees to freeze or succumb to mold, even if they have sufficient honey stores.