Sleeping bumblebees can survive underwater for a week

A lab mistake revealed that hibernating bumblebees can survive fully submerged underwater for at least seven days. This ability suggests the embattled insects are more resilient than previously thought.

Sabrina Rondeau stumbled upon the discovery while studying common eastern bumblebees (Bombus impatiens) in the lab at the University of Guelph in Canada. One week, she was checking on hibernating queen bees kept in a soil-filled tube “hibernacle” in the fridge when she realised that moisture had flooded the tube and plunged four of the insects underwater. “I kind of freaked out,” she says. “I was sure the queens were dead.”

To everybody’s surprise, the bees woke up unscathed after she drained the water. Rondeau had a hunch there was an undiscovered ability at play.

She systematically drowned 21 queens for seven days, and 17 of them – 81 per cent – made it through the floods. “That’s an extremely high survival rate, and it’s not significantly different from [hibernation survival] when there’s no water,” says Rondeau. This achievement is probably due to the fact that dormant bees drop their metabolism rate, which means they need very little oxygen and can make do with the air stored inside their bodies.

“Wow, the fact that you can submerge a terrestrial animal in water for a week and find that it’s still alive is indeed very surprising,” says Lars Chittka at Queen Mary University of London.

While male and worker bees die before the winter, hibernation allows queen bees to weather the cold for up to eight months, then wake up in spring to start a new colony. The number of queens that will survive is directly related to future population growth.

Since these bees hibernate in the ground, extreme weather can destroy their safe space. “It’s a pinch point in their life cycle,” says Nigel Raine, Rondeau’s PhD supervisor at the University of Guelph in Canada. That is a problem, as about one-third of all bumblebee species are already declining. Discovering they are physically adapted to survive a possible case of flooding is “really, really good news”, he says.