Over the past 12 years, the spread of Africanized honeybees, or "killer bees," has largely stalled in their northward expansion. While these bees are capable of surviving in colder climates, several behavioral and environmental factors limit their success in more temperate regions.
First, killer bees, when moved into colder environments, can exhibit a change in behavior that makes them act more like standard honeybees. Over time, they adjust to the local climate and lose their aggressive tendencies. Additionally, unlike European honeybees, Africanized bees tend to swarm frequently, a behavior that often leaves them with inadequate food stores. Swarming can reduce the colony’s strength, as half the hive leaves with the queen, leading to a lower overall population and fewer resources to survive the winter months.
Moreover, Africanized bees build smaller nests and store less honey, which works well in tropical regions but becomes problematic in areas with seasonal changes. In regions like North Florida, they may exhaust their spring honey supply during summer's dearth of nectar. By winter, these bees often don’t have enough honey reserves to sustain their colonies, leading to starvation rather than survival through colder periods. Additionally, their tendency to abandon nests, called absconding, results in leaving behind valuable resources that are critical for winter survival.
Regional peculiarities also play a role in limiting their spread. For instance, North Florida's mild winters allow bees to fly when temperatures are above 50 degrees. However, the lack of blooming plants means they expend energy searching for nonexistent nectar, depleting their honey stores more rapidly than bees in regions with harsher winters where hives remain clustered and conserve energy. This tendency to forage even when resources are scarce weakens the colony and increases the likelihood of starvation.
In addition, Africanized bees have adapted to tropical climates where flowers bloom year-round, supporting their frequent swarming and absconding behaviors. As they attempt to survive in more northern regions, these adaptations work against them, especially during winter when food sources are scarce and bees rely on substantial honey stores. Combined with their natural tendency to establish smaller colonies with limited storage, these factors significantly reduce their chances of thriving in colder, seasonal environments.
Source: Reddit