UK hairy bumblebees ‘wait’ in heatwave.

The effect of heat waves is twofold for bumblebees.

The UK species are adapted to our historically cold climate – with thick, furry bodies that retain heat and powerful flight muscles that keep them warm during flight.

But in heat waves, their muscles generate more heat, and their thick coats and round bodies make it difficult to cool down.

The trust’s science manager, Dr Richard Common, said once temperatures reached around 28C to 32C, UK bumblebees could struggle to fly without heat. If they can’t fly, they can’t forage.

“They actually cook themselves from the inside out,” Comont says. “Once their internal body temperature is much higher than 40C, they literally start to die. They start to grow again.”

BeeWalk data shows that By 2022, the UK will have had three official summer heatwaves and the population will drop significantly when temperatures reach 40.3C.

Red-tailed, buff-tailed and common carder bumblebees – three of the country’s most common species – fell well below normal levels – 20%, 25% and 35% respectively – before falling into autumn as colonies struggled.

The results seemed to last beyond that winter. BeeWalk data shows that overall queen numbers were below average in March, April and May 2023.