Bumblebees may be at home in town and country, but now researchers have found at least one species that is even more adaptable: it can survive underwater.
Scientists have revealed that queens of the common eastern bumblebee, a species widespread in eastern North America, can withstand submersion for up to a week when hibernating.
With bumblebee queens known to burrow into the ground to hibernate, the researchers say the phenomenon could help them survive flooding in the wild.
The team said its next priority was to investigate whether the results apply to other species of bumblebee.
“We know that around a third of all bumblebee species are currently in decline [but] this is not the case with [the common eastern bumblebee],” said Dr Sabrina Rondeau of the University of Guelph in Canada, adding that the team was keen to learn whether flood tolerance might play a role in their resilience.
Rondeau and her co-author, Prof Nigel Raine, first made their discovery when an accident in the laboratory led to water entering containers in which hibernating queen bees were kept.
“After that, curiosity naturally led to conducting a full experiment with many replications,” Rondeau said.
Write in the journal Biology Letters, the scientists describe how they took 143 unmated, hibernating queens of the common eastern bumblebee and placed each in its own plastic tube containing moist topsoil. The tubes were then fitted with perforated lids and kept in a dark refrigerated unit for a week.
After checking the bees were still alive, the researchers kept 17 tubes as controls and added cold water to the remaining 126. While the queen was allowed to float on top of the water in half of these tubes, it was pushed underwater by a plunger in the other.
For both conditions, a third of the tubes were each left for eight hours, a third for 24 hours and a third for seven days, simulating different flood conditions. The team then transferred the bees to new tubes and monitored their survival.
The results show that survival rates were similar regardless of the duration and conditions the queens were subjected to – indeed, 88% of the controls, and 81% of the queens submerged for a week were still alive at eight weeks. However, queens with a higher weight had a higher chance of survival.
The researchers say the findings are unusual, as most insects hibernate as adults – including many ground beetles – cannot cope with submersion in water and must leave floodplains to survive.
While Rondeau said it’s likely that queens of other bumblebee species are also flood-tolerant, ground-nesting bees — which include some species of bumblebee — can still be affected by flooding as their larvae may not survive.
Among future areas of research, the team said it would be interesting to investigate the mechanisms that support the queens’ resilience to flooding – with their low oxygen requirements during hibernation among possible important factors.
Prof. Dave GoulsonA University of Sussex bee expert who was not involved in the work said bee enthusiasts had long speculated that increased winter rain amid the climate crisis could drown many queen bumblebees as they hibernate underground.
“Surprisingly, this new research shows that hibernating queen bumblebees are completely unaffected by being submerged in water for up to one week,” he said. “This appears to be one small aspect of climate change that we don’t need to worry about.”
