Bees and pollinators are under attack in many ways. But they’re also showing resilience that seems outright incredible.

Sabrina Rondeau, a postdoctoral fellow now at the University of Ottawa, made the discovery almost by accident. She was studying hibernating queen bumblebees when she opened a refrigerator and found several of the bees submerged in water. The cause: condensation had crept into the soil-filled tubes where the bees had been stored, mimicking their underground winter burrows.

“I freaked out,” said Rondeau, who had been conducting the experiment for her doctoral studies. “It was only a small proportion… so it was not that big of a deal, but I didn’t want to lose those bees.”

To her shock, the bees survived. Rondeau had no idea the bees could do this. She asked around, trying to see whether anyone had any clues. No one did.

“I’ve been studying bumblebees for a very long time. I’ve talked about it to a lot of people and no one knew that this was a possibility,” she said.

An impressive skill, but why?

So, she set up an experiment to see just how long queen bees could survive underwater.

In the carefully controlled experiment, the researchers exposed 143 hibernating Bombus impatiens queens — one of North America’s most widespread bumblebee species — to simulated flooding conditions. Some queens floated on water. Others were held completely underwater with a plunger-like device. Each group remained submerged for eight hours, 24 hours, or a full seven days.

Afterward, the bees were dried off, returned to soil, and monitored for eight weeks.

The survival rates were stunning: 81 percent of queens that had been underwater for a week were still alive two months later — nearly matching the 88 percent survival rate of those never submerged at all.

This all begs the question: why? Why would bees have evolved such a spectacular ability?

Built for the unexpected

Bees are terrestrial creatures, they’re not designed to be underwater. But queen bees have a remarkable lifestyle. After mating in the late summer or fall, they spend the winter alone underground, entering a state of diapause where their metabolism slows dramatically.

Biologists have long known that bumblebee queens hibernate underground from late fall until spring. This period of dormancy—called diapause — can last up to nine months. During it, the queens slow their metabolism dramatically, needing very little oxygen. It’s possible that during this period, they could also face rising water levels, whether due to flooding or other factors. If this is the case, then bees that can withstand drowning have an advantage and pass down this ability selectively.

Of course, this doesn’t mean the water didn’t affect the bees at all. They seemed fine, but their health will need to be monitored for longer to see if there are any adverse health effects. Also, the study would need to be replicated on more species to see whether this trait is widespread.

Potentially crucial adaptation

But this is good news. Climate change is causing increasing flooding and flash floods, especially in urban areas. At the same time, pollinators like bees are under unprecedented threat. Many species are experiencing population crashes due to habitat loss, pesticide exposure, and changing weather patterns. But the common eastern bumblebee is among the more robust species, showing fewer signs of decline. This trait might be part of the reason.

“So, we are also wondering whether this resistance to flooding can be part of why they’re doing so well,” said Rondeau. “But it’s encouraging to know that at least (flooding) is not another big threat that we have to consider,” she said.

Journal Reference: Sabrina Rondeau et al, Unveiling the submerged secrets: bumblebee queens’ resilience to flooding, Biology Letters (2024). DOI: 10.1098/rsbl.2023.0609