What causes bees to exhibit "robber" behavior?

Robber behavior in bees is primarily driven by the scarcity of food resources. When bees are unable to find enough nectar or pollen in their environment, they may resort to raiding other hives in search of food. This behavior is often more pronounced during times of drought or when there is a sudden reduction in forage availability, as the competition for limited resources becomes fierce.

During these conditions, bees from weaker or food-deficient colonies may venture into stronger hives, seeking to steal honey or other food stores. This not only poses a threat to the robbed hive but can also lead to increased aggression and conflict between the colonies involved. This behavior is a natural instinct for survival, as bees seek to maximize their chances of nourishment when external food sources are depleted.

Factors like high temperatures or overpopulation may influence general hive behavior and resource availability but do not directly lead to robber behavior like food scarcity does. Similarly, the presence of chemicals might affect bee physiology or behavior but would not inherently drive them to seek out other colonies for food.