Bumblebees may self-medicate when exposed to fungal infections

There is an old saying that nature is the best medicine, and it turns out bumblebees might agree. A new study published in the journal Royal Society Open Science suggests that buff-tailed bumblebees (Bombus terrestris) may self-medicate when exposed to a fungal brood disease.

Nature’s pharmacy

It’s already known that some animals try to heal themselves when ill. For example, wild chimpanzees have been shown to reach for plants with pain-relieving and antibacterial properties, and some birds line their nests with cigarette butts because the chemicals ward off mites. Previous studies have also shown that honey bees with some types of infections collect more protective plant resin.

In this research, a team at KU Leuven in Belgium and the University of Valladolid in Spain investigated whether buff-tailed bumblebees change their foraging habits when exposed to different pathogens.

To find the answers, the scientists studied 18 commercial bumblebee colonies that were placed inside flight tents. In each tent, eight robotic flowers (four blue and four yellow) produced microdoses of artificial nectar containing either plain sugar water or sugar water with quercetin. This natural compound, found in plant nectar and pollen, is known to have antimicrobial properties.

Before the experiment, the colonies were split into three groups for two weeks. Some were exposed to Ascosphaera apis, a fungus that primarily infects and kills bee larvae, while others were exposed to Serratia marcescens, an opportunistic gut bacterium that infects adult bees. A control group was fed pollen with a sterile sugar solution.

A sensor inside the central feeding hole of each robotic flower recorded every visit, and the flower automatically refilled the nectar after each visit.

A tailored response to illness

Over five days of free foraging, colonies exposed to the fungus Ascosphaera apis became increasingly likely to visit the quercetin-laced flowers and spent more time drinking from them.

However, those exposed to the bacterium Serratia marcescens showed no significant change in their preference for quercetin nectar as the experiment progressed. Colonies from the healthy control group also showed no significant change in their preference for quercetin nectar.

So while the researchers observed a clear behavioral shift toward quercetin nectar, it did not occur for both types of pathogens, suggesting that disease type matters. “Overall, these results indicate that pathogen identity shapes behavioral plasticity in nectar foraging,” wrote the study authors in their paper.

However, because the study did not measure whether drinking quercetin actually reduced infection levels or helped more larvae survive, the findings should be treated with caution. “Our results do not provide a definitive demonstration of formal self- or social medication.”

Who’s behind this story?

Paul Arnold

BSc Biology from University of London. BBC documentary producer with world travel experience. Freelances from southern Spain.

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Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021.

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Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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