Breeding bees that mitigate survival risks under normal fall and winter weather patterns, and exhibit enhanced survival capacity during atypical but increasingly frequent climate and weather extremes
Beekeeping and colony management get tricky as winter approaches. Because many natural colony responses to changing environmental cues will make problems more difficult to spot and more challenging to remedy with the usual management techniques, it also may prove that at some point it may be more cost effective to let nature take its course and try again in the spring if your colony fails to make it to spring.
Genetic factors can also affect colony behavioral and physiological traits to the approach of winter. The result is that colonies from genetic populations that exhibit distinct phenotypes (after exposure to the same stimuli) may have discernable survival advantages in some environmental conditions. To amplify this point it is beyond question that some traits prized by many beekeepers, because they favor colony phenotypes that beekeepers find advantageous (like building big brood nests in early spring and initiation of oviposition by queens in response to colony feeding) may in fact be maladaptive for colony survival under unpredictable climatic conditions, and even normal patterns of temperature and weather variability between one year and the next.
We at BeeWeaver have spent many years deliberately selecting for honey bees that quickly respond to environmental changes in ways that we believe confer survival advantages under a spectrum of natural conditions that colonies can be expected to confront – especially over the long term. What does this mean as a practical matter?
Fundamentally it requires forsaking the attributes of commercially popular strains that many beekeepers value, and instead focusing on what the bees need to do to emerge from a winter that is earlier, longer, and harsher than normal, or a spring that is later, colder or more intermittent than usual or a combination of those events.
To illustrate, I will discuss one pattern that we have confronted much more often over the past three decades than we did for the first 80 years of the 20th century, and how we’ve used that experience to refine our efforts at selecting bees that can handle whatever nature throws at them. One of the weather patterns that seems to have become increasingly common over the last several years is that falls are drier, and late fall and early winters colder than normal, while the warmth in the spring develops earlier for a sustained interval but then reverts to cold and wet at about the time in the spring when we once could bank on increasingly stable warmth and relatively uninterrupted pollen flows. These new patterns pose a variety of challenges for bees, and the beekeepers that are managing them.
As you may know, bees don’t require tremendous amounts of honey to survive winter, as they allow their interior hive temperatures to dip into the 50s or upper 40s (because there is no brood present). Conversely, once brood rearing begins in late winter or early spring, colonies will consume large quantities of honey as they begin to keep increasingly large areas of brood incubated at 90+ degrees Fahrenheit.
So let’s think explicitly about the consequences of keeping hives with commercially popular bees that rear brood so long as they are being fed in the fall, and then quickly ramp up brood production again in the spring (and in some geographic locations never go broodless at all). If colonies are still rearing brood when the cooler temperatures of fall arrive, and especially if brood remains when temperatures plunge in late November or early December then hives will deplete their winter stores keeping the interior of the hive warm instead of allowing the inside temperatures to drop with the onset of cold weather. Of course, beekeepers can feed more to compensate, but at a minimum this becomes more costly and worse, for those queens that respond to the stimulus of feeding with more egg laying it becomes a self-reinforcing problem. The same holds true on the other end of winter – if colonies initiate a rapid increase in brood rearing on the first signals of spring or the first feeding by beekeepers during the initial warm interval, then colonies will be more likely to starve or have chilled brood if temperatures suddenly drop again and remain low.
We prefer to see colonies match their reproductive efforts to the natural environmental signals, which means that we want colonies that stop rearing brood when fall pollen flows abate or temperatures begin to drop. And we want that response to be faster if the hive has smaller stores of honey going into winter. So for instance, if one has two colonies in the same apiary, and one is a late summer or fall split that has a smaller population of adult bees, and fewer combs of honey going into winter we want to see that colony stop brood rearing ahead of another hive in the same yard that is full of bees and has a full deep of honey put away for winter. The later colony can afford to have some brood still present in late November, but the smaller hive may get into trouble if it is matching the brood rearing activity of the stronger, heavier hive. Many of the same considerations apply to the colony reproductive behavior that we like to see in late winter or early spring. We value hives that begin brood rearing shortly after the first spring pollen flow begins, but we regard colony performance as too exuberant if the hive goes to unrestrained brood nest expansion immediately. Too often that colony that launches into uninhibited brood rearing will run out of pollen or honey if cooler, wetter weather returns, unless the beekeeper immediately feeds and/or provides pollen substitute when the weather turns.
Of course there is another benefit to rearing colonies that respond appropriately to the signals of imminent winter or incipient spring – in the age of Varroa destructor parasitism there is an additional advantage to colonies that enter a broodless period earlier and restrain brood rearing until it is truly spring. During broodless intervals Varroa reproduction is halted, and mites are all phoretic, living on adult bees where they are more exposed to various hazards and bee behavior that increase mite mortality. The end result is a reduction in Varroa populations over time, and fewer mites surviving winter and ready to begin infesting and reproducing once brood rearing returns.
It is a relief to realize that traits conferring a survival advantage to environmental risks – overwintering capacity – can also help cope with one of the most serious biological threats that colonies face, Varroa mites.