Bees employ various strategies to survive winter. Unlike many insects that disappear or enter dormancy, bees adapt to freezing temperatures and scarce resources. Their methods depend on their species and social structure.
Honey Bees: A Collective Survival
Honey bee colonies survive winter as a cohesive unit. Instead of hibernating individually, thousands of worker bees form a tight cluster around their queen within the hive. This “winter cluster” functions as an incubator to generate and conserve heat.
The bees on the inside of the cluster continuously vibrate their flight muscles without moving their wings, producing metabolic heat. This collective shivering allows the colony to maintain a core temperature, often between 75 and 93 degrees Fahrenheit (24-34°C), even when outside temperatures drop significantly below freezing. Bees on the outer layers of the cluster pack together tightly, acting as an insulating shell, while those in the center rotate, ensuring no individual bee freezes.
To fuel this constant heat production, honey bees rely on stored honey for energy. The colony collects large quantities, often needing 60 to 90 pounds to sustain themselves through winter. During this period, the queen reduces or ceases egg-laying, and the colony’s focus shifts to maintaining warmth and consuming reserves. “Winter bees,” born in the fall, are physiologically different; they have larger fat bodies and live for several months, unlike summer bees, making them suited for this long period of collective survival.
Solitary and Bumble Bees: Individual Survival
In contrast to honey bees, solitary bees and bumble bees use individualized methods for winter survival. Adult solitary bees complete their life cycle by autumn. Their survival hinges on the next generation, which overwinters in a protected, dormant state.
The offspring of solitary bees, such as mason or leafcutter bees, develop into larvae or pupae and remain in sealed nest cells throughout the cold months. These nests, often in hollow stems, wood tunnels, or underground burrows, are provisioned with pollen and nectar by the female bee. The developing bees enter diapause, a period of suspended development, emerging as adults when spring arrives and conditions become favorable.
Bumble bees also have an annual life cycle where most of the colony dies off with winter’s onset. Only the new, fertilized queens survive the cold season. These queens find secluded spots, known as hibernacula, to hibernate alone, often burrowing into soft earth, under logs, stones, or thick moss. The hibernating queen emerges in spring, strengthened by autumn fat reserves, to establish a new colony.
Key Elements for Winter Survival
Several elements are crucial for any bee’s successful winter survival. Adequate food stores are necessary; for honey bees, this means sufficient honey reserves, while solitary bee larvae depend on provisions left by their mothers. Without enough nourishment, colonies or individuals may not have the energy to endure the cold months.
Suitable shelter and insulation are also important. For honey bees, a well-maintained hive that offers protection from wind, moisture, and extreme cold is important for cluster temperature. Bumble bee queens require a secure, insulated hibernation site, and solitary bee cocoons benefit from protected nest locations. Consistent cold temperatures are beneficial; false thaws can prematurely rouse bees, causing them to expend valuable energy before spring.
Bee health entering winter affects survival chances. Pests like Varroa mites, which weaken bees and transmit diseases, can compromise a colony’s strength. Summer weather, including rainfall and temperature, influences nectar and pollen availability, directly impacting food gathering for winter. Strong, healthy bees with ample resources are better equipped to withstand winter’s challenges.