Bees, recognized as pollinators, are sensitive to environmental conditions. Their ability to thrive and contribute to ecosystems is closely linked to temperature and their capacity to manage thermal challenges.
How High Temperatures Affect Individual Bees
Excessive heat impacts individual bees. Bees face dehydration when temperatures rise, leading to decreased movement and slower responses. High temperatures can induce metabolic stress, altering energy pathways within a bee’s body. Research on bumblebees indicates that elevated temperatures affect survival rates and appetite.
Extreme heat can cause the denaturing of proteins and enzymes. Their disruption can lead to a cascade of internal failures, as these are essential for numerous life functions. While honey bees exhibit metabolic adjustments to tolerate heat, prolonged exposure to temperatures above their optimal range can still lead to individual distress. For example, adult male bees can experience reduced activity, shorter lifespans, and elevated mortality risk following heat shock.
How Bee Colonies Regulate Heat
Bee colonies employ collective strategies to maintain a stable internal hive temperature, typically around 93-95°F (34-35°C). This temperature is crucial for brood development and overall colony health. One primary method is fanning, where worker bees rapidly beat their wings to circulate air through the hive. This action helps draw cooler air in and expel warmer, humid air, effectively creating an air-conditioning system.
Bees also collect water for evaporative cooling. Worker bees bring water droplets back to the hive, spread them over comb surfaces, and then fan their wings to evaporate the water, cooling the hive interior. During hot periods, a colony’s water demand can be substantial, potentially requiring up to a liter per day. Another visible behavior is “bearding,” where a portion of bees cluster outside the hive entrance, reducing the bee density inside and creating more space for air circulation and removing excess body heat. Bees also use propolis, a resinous material, to manage hive ventilation by regulating the size of the hive entrance.
When Heat Becomes Lethal for Bees
Despite their sophisticated thermoregulatory mechanisms, bee colonies can succumb to extreme heat when temperatures exceed their capacity for regulation. Heat stress can weaken a colony, making it more susceptible to pests and diseases. When external temperatures consistently rise above 95°F (35°C), bees experience heightened stress, leading to reduced foraging activity as they prioritize cooling the hive.
Critical temperature thresholds exist where colony regulation fails. If hive temperatures rise above 94°F (34.4°C), the brood (eggs, larvae, and pupae) can be harmed, leading to abnormal development or death. Signs of severe heat stress in a colony include unusual clustering outside the hive, excessive fanning, reduced foraging, lethargy, and in extreme cases, melted wax and damaged comb structures.
Prolonged exposure to temperatures above 40°C (104°F) causes immediate physiological stress, forcing bees to abandon normal duties to focus entirely on cooling. Male honey bee drones are particularly sensitive to heat; temperatures above 107°F (42°C) can cause them to spontaneously ejaculate and die within hours, impacting queen mating opportunities and colony viability. Ultimately, if a colony’s cooling mechanisms are overwhelmed, it can lead to widespread adult bee mortality and colony collapse.