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Red-tailed bumblebee (Bombus lapidarius) by Andy Benson

I’ve found a dead bumblebee

It can feel sad to see a dead bumblebee but it’s not unusual to find them throughout the spring, summer and autumn.

A dead Red-tailed bumblebee on the ground.
A hand holding several dead bumblebees.

Annie Ives

Can I find out what happened to it?

It’s not usually possible to say for sure what caused the death of a bumblebee. There are a number of reasons why bumblebees might die, such as predation, collision with vehicles, lack of food, prolonged bad weather, disease and parasites. Also, when nests are active and producing worker bumblebees, the natural life span of a bumblebee can be as little as a few weeks. At the end of the nesting period only the new queens survive by hibernating over winter while all the workers and male bumblebees die off gradually. When they are close to death, they often cling to flowers and look quite lethargic. When they do die, they then drop off the flowers, and it’s possible to find a number of dead bumblebees in the same spot, especially near the most bee-friendly plants. Dead bumblebees, and sometimes larvae, can also be found near bumblebee nest entrances, because the workers remove them to make space and prevent disease.

I’ve found a number of dead bumblebees under Lime trees

Sometimes, a large number of dead bumblebees can be found under Lime trees. The current research evidence suggests that a combination of low sugar content in the nectar, with the possible presence of an addictive metabolite, affects the bumblebees’ decision making. This results in bumblebees continuing to feed, despite not getting the energy they need from the nectar. The issue can be made worse when air temperatures are low as bumblebees require more energy to warm up for flight. Sadly, these bees can become grounded and may starve as they do not have the energy to fly. It’s not as bad as it sounds though as not all bumblebees are affected in the same way and some appear to remain healthy while feeding on lime trees. It could be that the bumblebees that are affected are approaching the end of their lifespan or weakened in some other way.

A White-tailed bumblebee preparing to land on white willow catkins.

Andy Jones

I’ve found lots of dead bumblebees with holes in them, what happened?

At certain times of year, such as spring, bumblebees can be attracted in large numbers to flowering plants, like willow trees. Some birds have learnt that this is a good source of protein, as they are also preparing for the breeding season, and will catch the bumblebees. Once a bird has caught a bumblebee, they will often return to the same spot to remove the sting and feed on the inner parts of the bumblebee before discarding the outer exoskeleton. A little pile of dead bumblebees with distinctive holes can accumulate nearby. Overall, predation by birds isn’t thought to have a big impact on bumblebee populations.

Has this dead bumblebee been poisoned by weedkiller or another pesticides?

Pesticides are a problem for bumblebees but large-scale poisoning events are very rare. It’s usually not possible to say for sure what the cause of death was. However, if you find dead bumblebees and suspect that they might have been poisoned by the professional use of pesticides meeting the criteria set out on the Health and Safety Executive website then please report this to the Wildlife Incident Investigation Scheme (WIIS) on 0800 321600.