Updated: 25th February 2021 Show
What happens to bees when the weather grows cold? Where do bees live in winter? Do bees hibernate in winter, and how do they survive the low temperatures and stormy weather? We may still see bees around in the autumn on dry days, feeding from the flowers on ivy - Hedera helix, and pollinating autumn raspberries (and other late crops). But what happens then? Do bees hibernate? If so, where do bees hibernate?It really depends on the species, but in summary:
Given the many bee species in the world, there are of course, exceptions to those scenarios described above. One key factor is climate: in exotic locations, species may be active throughout the year. In such circumstances, there remains sufficient abundance of the right kinds of foods to keep the bees active. Leafcutter bee visiting geranium flower.Why do bees hibernate in winter?In cooler climates (rather than exotic locations) where there are far fewer flowers from which to feed in the winter, bees need to shelter from the weather and conserve their energy until the flowers are blooming again. Below we'll cover in turn, more detail about the winter habits of:
Where Do Bumble Bees Go In Winter?Here is a nice little quote that sums up the situation for many wild bees, including
bumble bees: "The most common forms of overwintering in non-active bees involve either a prepupa or a fully developed, non-emerged adult within the birth cell. Eventually, rising temperature or some other physiological cue will trigger the bee to emerge. Bumblebees are different in that the new queens produced in late summer feed up on flowers and then depart
their birth nest, find an old rodent hole or some other pre-existing cavity (including compost heaps) and hibernate in this." - Steven Falk - entomologist and author of Field Guide to Bees Of Great Britain And Ireland.
Hibernation sites vary, but it seems most bumble bee species prefer soil banks (perhaps in an abandoned rodent hole) and slopes, and preferably in the shade or in a North West facing position (Goulson). However,
I have read reports of bumble bee queens being disturbed during their hibernation, because they have been found taking their winter snooze in the soft potting compost in a plant pot, or in a pile of wooden logs. They may also seek winter refuge in a compost heap. Are changes in climate affecting hibernating patterns of bumble bees - such that we even witness winter active bumble bees?In milder climates – and even in milder weather zones of countries such as the UK, bumble bees have been known to remain active through the winter foraging on mahonias or other late/winter blooming shrubs and flowers in public parks. If winters are getting warmer, perhaps this should not surprise us. In areas of South East Asia and South America, there are bumble bee species that have no annual life cycleas such that includes winter hibernation, and colonies can become rather large as a result, even reaching up to several thousand workers (Michener & Laberge 1954; Michener Amir 1977). In Brazil, the species Bombus incarum can produce as many as 2500 new males and queens in a single nest! (In the UK, bumble bee colony size varies, but will perhaps reach 150 – 400 workers. Where Do Honey Bees Go In Winter?Honey bee foraging on prairie mallow.In warmer climates, honey bees may be active all year, so that honey is essentially fuel for reproduction and swarming. In cooler climates, honey bees become less active, but not entirely dormant (inactive), and honey (winter food stores) is vital to help sustain the
colony. When the temperature falls below 10 °C the honey bee queen and workers huddle together in their brood chamber, in a temperature regulating cluster called a 'thermo-regulating cluster.' This is commonly referred to as a 'winter cluster'. By this time, there will be no males (drones) in the hive or nest. Older worker bees will form the outside of the cluster, with the younger bees toward the middle. The clustering bees vibrate their wing muscles in a kind of shivering movement, which helps to generate heat. The bees are also helped by their hairy bodies, because the fine hairs help to trap the heat, and this effect is magnified by the fact that there are lots of bees together, all with hairy bodies. The colder it gets, the more tightly the bees form their cluster. As younger worker bees in the middle of the cluster get warmer, they loosen the tightness of the cluster, allowing the warm air to circulate back to the older bees on the outer of the cluster. The outer temperature of the cluster is usually maintained at around 12 °C, but no less than 6 °C2. Amazing fact: Whilst honey bees shiver to keep warm during the winter, they create conditions that would be toxic to humans! Why? As the bees are shivering, they use oxygen and exhale (breathe out) carbon dioxide. This is happening in an enclosed space. In such an environment (carbon dioxide and restricted ventilation) humans could not survive, but the bees create such conditions intentionally because it decreases the bees' metabolic rate, and hence helps them to conserve their energy stores. This higher level of carbon dioxide can also help to kill off some pests, such as the Varroa mite1! Wild honey bee nest in tree. |