Not only do heat waves heat bumblebees. Additionally, it appears that the high temperatures significantly impair their sense of smell, which could be detrimental to the colonies’ ability to survive.
For bumblebees, the capacity to detect floral scents is critical to their survival. They find the nicest blossoms by olfactory and visual cues, which they then employ as a food source (SN: 4/9/24). However, insect ecologist Sabine Nooten and colleagues write in the August Proceedings of the Royal Society B that exposure to artificial heat waves lowered bumblebee antennae’s capacity to perceive floral odors by as much as 80%.
According to Nooten of the University of Würzburg in Germany, “the animals need to find a way to adapt somehow to cope with this,” as climate change is predicted to increase the intensity and frequency of heat waves.
It is known that climate change affects bumblebees (SN: 7/9/15). These insects are ideally suited to live in the coldest parts of the planet because of their thick, hairy bodies. However, in a world warming, being cold-resistant might become lethal. Thus, Nooten and her colleagues set out to investigate if heat waves could affect bumblebees’ capacity to detect floral scents.
By keeping the bees in tubes at 40° Celsius for about three hours, the researchers were able to mimic heat waves for over 190 individuals of two common species of bumblebees, Bombus terrestris and B. pascuorum. A portion was further placed in a dry atmosphere, a portion had access to sugary materials, and a portion was allowed to recuperate at room temperature for a full day following the heat treatment.
Following the artificial heat waves, the scientists severed the bees’ olfactory sensory neurons in the antennae to see if the insects could still identify chemical compounds known as flower smells that are present in a wide variety of flowers.
Because the workers are exclusively female and feed the hive, they were more affected than the males by up to an 80% reduction in the strength of the electrical signal from the neurons caused by the heat waves. Even worse, after having a full day to calm down, the bees’ antennae still lacked their ability to smell. That caught me off guard, Nooten remarks. The crew anticipated that those antennae will reattach. She claims that the fact that they didn’t indicates that the bees don’t heal quickly, which is bad news for the colony’s ability to obtain food.
Nooten speculates that the detrimental impact of heat waves on worker bumblebees’ sense of smell may really have a domino effect on the colony’s ability to survive. It might account for some of the numerous [bumblebee population] decreases observed, she says, along with other elements like habitat degradation.
Dave Goulson, a bumblebee ecologist from the University of Sussex in Brighton, England, who was not involved in the study, thinks the findings “seem pretty solid.” According to him, the shape of the antennae is very uniform among bee species. “It seems likely that other bees would suffer in the same way if bumblebees suffer in this manner. However, we won’t be certain until someone looks.
