When Sabrina Rondeau flooded the tiny containers holding hibernating bumblebee queens in her University of Guelph laboratory, she expected casualties. Instead, nearly nine out of ten queens survived a full week underwater, a result so striking it reshaped what entomologists thought they knew about one of North America’s most important pollinators.
The findings, published across two peer-reviewed papers in spring 2025 and early 2026, reveal that eastern bumblebee queens (Bombus impatiens) possess a previously undocumented ability to breathe underwater during winter dormancy. As flooding events grow more frequent across temperate regions, that ability may be a critical, and until now invisible, line of defense for wild pollinator populations.
A week underwater and still alive
The first study, led by Rondeau and her supervisor Nigel Raine and published in Biology Letters, tested 143 diapausing queens alongside a 17-queen control group. Queens were submerged completely in water for up to seven days under controlled laboratory conditions. Survival averaged roughly 89.5%, with a standard error of 6.4%. Crucially, that rate held whether queens floated near the surface or sat fully submerged on the bottom, suggesting the survival mechanism does not depend on occasional access to air.
“These queens are in diapause, a state of deep dormancy, so their metabolic demands are already extremely low,” Rondeau explained in a University of Guelph summary of the work. “But we wanted to know what was actually keeping them alive underwater.”
Three systems working together
The answer came in a follow-up study published in Proceedings of the Royal Society B. Rondeau and Raine measured carbon dioxide output, dissolved oxygen levels in the surrounding water, and lactate concentrations inside the queens’ bodies during and after submersion. The results pointed to a three-part survival strategy that no one had previously documented in bees.
First, the queens suppress their already minimal winter metabolism even further, reducing oxygen demand to a fraction of normal levels. Second, they extract small but measurable amounts of oxygen directly from the surrounding water, a form of low-level underwater gas exchange confirmed by steadily declining dissolved oxygen readings in the experimental containers. Third, they partially switch to anaerobic metabolism, the backup energy system organisms use when oxygen runs short. Lactate buildup in the queens’ tissues provided the chemical signature of that switch.
The recovery phase offered its own clue. When queens were removed from water, their CO2 output spiked sharply before settling back to baseline. Physiologists recognize that pattern as “oxygen debt” repayment: the body rapidly clearing metabolic byproducts that accumulated during oxygen-limited conditions. The spike confirmed that the queens had been operating in a genuinely oxygen-deprived state, not simply holding their breath with a comfortable reserve.
What the lab cannot replicate
Laboratory survival rates, however encouraging, do not automatically translate to the wild. Real-world flooding exposes hibernating queens to variables the experiments did not test: fluctuating soil temperatures, sediment pressure, waterborne pathogens, and chemical contaminants from agricultural or urban runoff. No field-based survival data currently exist for Bombus impatiens queens during actual flood events, so the 89.5% figure represents a best-case benchmark under controlled conditions.
The research also examined only one species. Whether other bumblebee species share the same capacity is unknown. A University of California Agriculture and Natural Resources overview notes older observations of various bee species recovering after water exposure, hinting at broader adaptations across bee lineages, but those accounts predate modern experimental methods and lack physiological detail.
There is also the question of what happens to the rest of a colony. Queens hibernate alone underground, but active nests hold larvae, workers, and food stores that may be far more vulnerable. Independent bee researchers reviewing the earlier Biology Letters paper noted that while queen survival is encouraging, larvae and other colony members face distinct and potentially fatal risks from the same flood events. Whether queens that survive submersion go on to found successful colonies at normal rates has not been studied.
What this means for pollinator protection
For gardeners, land managers, and conservation practitioners, the practical message is specific and useful. Bumblebee queens hibernating in soil are substantially tougher than previously assumed. A stretch of waterlogged ground during winter or early spring does not automatically spell local queen mortality. That knowledge could influence decisions about drainage management in pollinator habitat areas, where well-intentioned interventions sometimes disturb overwintering sites.
But the research also draws a clear boundary around its own conclusions. It says nothing about whether repeated flooding, submersion lasting longer than seven days, exposure to contaminated water, or disturbance during the post-submersion recovery phase would change outcomes. The safest reading, as of May 2026, is that queens possess a remarkable physiological buffer against short-duration winter floods, one that likely evolved long before human-driven climate change began intensifying those floods. How far that buffer stretches under worsening conditions is a question the science has not yet answered.
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*This article was researched with the help of AI, with human editors creating the final content.
