Researchers at the University of Guelph inadvertently discovered that bumble bees can survive being fully submerged in water for a week without apparent difficulty.Victoria MacPhail/Supplied
What began as a science experiment gone awry has turned into the unexpected discovery of an insect superpower.
Hibernating bumblebees, it seems, are virtually undrownable – to the extent that they can be fully submerged in water for a week and survive the experience without apparent difficulty.
Researchers say the finding is relevant to future conditions as climate change renders areas where bees hibernate more susceptible to spring storms and flooding.
“I think it’s very encouraging news,” said Sabrina Rondeau, a biologist and postdoctoral researcher at the University of Ottawa. “One-third of all bumblebee species around the world are in decline right now, and so if we are able to discard flooding as being a potential threat to bees, then we can focus our attention on other threats that we know for sure are harming them.”
Dr. Rondeau was first alerted to the bees’ uncanny ability in 2021, when she was based at the University of Guelph and working on an experiment to determine how hibernating queen bumblebees are affected by pesticide residue in soil.
It is only queen bumblebees that hibernate, which they do by digging underground burrows for themselves in the fall. When spring arrives they emerge and begin new colonies, which in turn raise the next generation of queens.
For her experiment, Dr. Rondeau received a shipment of 300 hibernating common eastern bumblebee queens, the most plentiful species in eastern North America. The queens were kept in a refrigerator to maintain their state of hibernation. Then, condensation in the fridge dripped onto the bee containers, filling four of them up so that the queens inside were inundated by water for an extended period of time before the problem was discovered.
“I was sure that the queens were dead,” Dr. Rondeau said. “I removed the water and – surprise, surprise – they were still alive.”
Neither Dr. Rondeau nor her supervisor, Nigel Raine, a professor at Guelph who specializes in pollinators, had seen any previous studies documenting bumblebee resistance to drowning. That got them curious, so they devised a new experiment.
Using 143 queens that were left over from the initial study, the researchers set aside 17 and kept them in containers with soil but with no water. These were the controls for the experiment. Containers with the remaining queens were filled with water. In some cases the queens were allowed to float, simulating periods of high groundwater rising into burrows. In other cases queens were deliberately held underwater using a plunger. The wet conditions were maintained for different groups of bees over eight hours, 24 hours and seven days, to mimic floods of differing severity.
Remarkably, nearly all of the bees that were placed in water lived. Their survival rate of about 90 per cent was similar to that of the control group that had no water exposure. Afterward, all the bees were then stored in fresh, dry containers with soil and checked again at four weeks and eight weeks. Those that had experienced submersion fared no worse than the others.
The study, published Tuesday in the journal Biology Letters, did not establish an upper limit on how long the queens could survive underwater and Dr. Raine said the figure may lie somewhere well beyond one week. It’s also not clear how the bees managed the feat. The hibernating bees would not need much oxygen to survive, but where it came from or how it is conserved in their bodies is unknown.
Sheila Colla, a conservation biologist and bumblebee expert at York University who was not involved in the study, said the finding shows how much remains to be discovered about bumblebees, particularly outside of their most visible activity of foraging around flowers.
“It highlights the fact that if we’re talking about the conservation of insects, we need to understand the whole life cycle,” she said.
She cautioned that the bumblebees’ ability to survive immersion may not extend to other bumblebee species, including those that are endangered and cannot be easily studied. Such differences could shed light on why some species are currently faring better than others, she added.
“Like all good science, it raises a heck of a lot of other questions for us,” Dr. Raine said.