Bees have developed various ways to survive the colder months. While some insects enter a state of true hibernation, bees employ diverse strategies, from communal warmth to individual dormancy. Understanding these methods reveals the remarkable adaptability of different bee species to environmental changes.
Honey Bee Winter Survival
Honey bees (Apis mellifera) do not hibernate; instead, they remain active within their hive throughout winter. When temperatures drop below approximately 50°F (10°C), worker bees form a tight cluster around their queen and any developing brood. This “winter cluster” is a highly organized structure where bees on the outer layer pack together tightly, acting as an insulating mantle.
Bees inside this cluster generate heat by rapidly contracting their flight muscles without moving their wings, a process often described as shivering. This metabolic activity allows the colony to maintain a core temperature of around 92-97°F (33-36°C) within the cluster’s center, even when outside temperatures are freezing. The queen typically resides in this warm core, ensuring her survival.
To fuel this continuous heat production, honey bees rely on the honey stores they collected during warmer months. Worker bees inside the cluster feed on this honey, and those on the outer layer periodically rotate inward to access food and warmth. A healthy honey bee colony needs 80-100 pounds of honey to sustain itself through winter. The colony’s survival depends on sufficient food reserves and maintaining the cluster’s integrity.
Bumble Bee Winter Survival
Bumble bees (Bombus species) employ a distinct winter survival strategy. Unlike honey bee colonies, most of a bumble bee colony perishes with the arrival of cold weather. Only newly mated queens survive to establish new colonies the following spring.
These mated queens seek sheltered locations to hibernate individually. Common hibernation spots, known as hibernacula, include soft, well-drained soil, leaf litter, rotting logs, or abandoned rodent burrows. Queens often choose north-facing slopes or raised areas to avoid direct winter sun, which could cause them to emerge too early. They dig small chambers, typically 5 to 15 cm deep, where they remain in a state of torpor, a deep inactivity similar to hibernation.
During this period, the queen’s body produces a natural antifreeze substance, such as glycerol, to prevent ice crystals from forming in her tissues. She remains dormant until spring, emerging when temperatures rise and new floral resources become available. Upon emergence, she begins foraging to regain strength before searching for a suitable nesting site to lay eggs and start a new colony.
Solitary Bee Winter Survival
Solitary bees, a diverse group including mason bees, leafcutter bees, and mining bees, exhibit similar winter survival strategies. Unlike social bees, adult solitary bees typically complete their life cycle and die before winter arrives. Their survival depends on the next generation, which overwinters in an immature stage.
The offspring of solitary bees usually spend the winter as larvae or pupae, protected within their natal nests. These nests can be found in various locations depending on the species: some burrow into the ground, others utilize hollow plant stems, and some construct cells in tunnels within wood or mud. Each larva or pupa is provisioned with “bee bread” (pollen and nectar) as its food source until it develops into an adult.
The young bees remain in a dormant state within these protected chambers throughout the cold months, completing their metamorphosis. They emerge as adult bees in the spring or early summer, ready to begin their brief adult lives, mate, and create the next generation. The undisturbed nature of these nesting sites is crucial for their successful overwintering.
Supporting Bee Winter Health
Individuals can support bee health during winter by adopting practices that aid their survival. For solitary and bumble bees, leaving garden debris undisturbed provides essential overwintering habitats. Plant stalks and hollow stems, for instance, offer ideal nesting and protection sites for cavity-nesting solitary bees. Undisturbed leaf litter offers insulation and shelter for hibernating bumble bee queens and ground-nesting solitary bees. Avoiding excessive garden cleanup in autumn can significantly benefit these species.
Providing late-season nectar and pollen sources is also beneficial for bees preparing for winter. Planting fall-blooming flowers like asters and goldenrod allows bees to gather food reserves before cold temperatures set in. These late blooms help honey bees build up their honey stores and provide energy for bumble bee queens before hibernation.
For beekeepers, ensuring colonies have ample honey stores is important for winter survival. Beekeepers typically leave a significant portion of honey in the hive to sustain the colony through the colder months. Proper hive insulation and protection from wind and moisture can help honey bee colonies conserve energy and maintain internal warmth.