As global temperatures rise, bumblebees face significant challenges including nest overheating, which threatens their ability to maintain populations. New research highlights how increased heat can disrupt the construction and viability of bumblebee nests, which are essential for the development of healthy larvae.
Peter Kevan, scientist and professor from the University of Guelph, Canada (and lead author of the article published in Frontiers in Bee Science), emphasizes that the observed decline in bumblebee species across various regions may be linked to excessive heat within their nests, which becomes lethal when temperatures exceed 35° Celsius (95° Fahrenheit). Despite their capacity to regulate temperature, bumblebees find it increasingly difficult to adapt to rising temperatures, which exceed the optimal range of 28–32° Celsius for their nests.
Temperature regulation is crucial for individual bee survival, reproductive success, and overall health of the entire colony, which is a superorganism. The collective well-being of the colony directly affects its survival and reproduction capabilities.
Kevan’s extensive review of 180 years of scientific literature reveals that while bumblebees can survive temperatures up to 36° Celsius and thrive best at around 30–32° Celsius, variations exist between species and geographic conditions. Nonetheless, the similar optimal temperature range across different bumblebee species suggests a limited scope for evolutionary adaptation to increasing global temperatures.
Bumblebees have developed complex nesting behaviors and structures that help mitigate the effects of extreme heat. The architecture of their nests, often underground or in shaded areas, plays a pivotal role in maintaining optimal temperature conditions. These nests are intricately designed to enhance the colony's ability to regulate heat through natural insulation and ventilation mechanisms.
Research indicates that the material properties of these nests, such as their thermal buffering capabilities, are critical in shielding the developing brood from the harsh external temperatures. This natural engineering allows bumblebees to maintain a relatively stable internal environment, which is essential for the larvae's growth and the overall health of the colony.
The implications of this thermal stress are severe. High temperatures can lead to rapid metabolic breakdown in bumblebees, often resulting in death. Studies parallel to those on honeybees indicate that elevated nest temperatures could weaken bee queens, reduce the size and condition of worker bees, and consequently lead to less healthy offspring.
Scientists call for more studies focused on aspects of bumblebee ecology that are currently under-explored, such as nest morphology, material properties, and thermoregulation strategies. Innovative methods like ground-penetrating radar and flow-through respirometry analysis could provide deeper insights into how bumblebee colonies adapt their nesting behaviors to mitigate heat stress. Understanding these adaptations is crucial for predicting the resilience of different bumblebee species to ongoing climate change, ensuring their survival in an increasingly warm world.
