Bees Self-Medicate Preventively When Exposed to Infection!
A new scientific study published in the journal Royal Society Open Science reveals that bumblebees engage in preventive self-medication when exposed to infection. When their colonies are infected with a lethal fungus that can kill larvae, the bees alter their foraging behavior, shifting their food intake to nectar enriched with an antimicrobial compound. This represents a rare example of self-medication-like behavior in a social insect. The study, authored by Camille Devoiselle and colleagues, was published in 2026 in Royal Society Open Science.
The research team, led by Dr. Maria Pozo from the University of Valladolid in Spain and colleagues from the Catholic University of Leuven in Belgium, explained that the field of “zoopharmacognosy” studies how animals use natural compounds for therapeutic purposes, such as pain relief, combating infection, or preventing parasites. They noted that self-medication is a central behavior within this field, defined as the ability of an organism to consume organic compounds that stop, reduce, or prevent an existing infection, even though these compounds may be costly for healthy individuals. The team considered this behavior a form of adaptive flexibility, where individuals modify their diet in response to pathogen pressure.
Because therapeutic compounds are often toxic or nutritionally suboptimal, researchers hypothesized that self-medication would be limited to infected individuals, while healthy ones would avoid it. In this context, the study sought to determine whether social bumblebees of the species Bombus terrestris resort to self-medication when exposed to pathogens.
Researchers used artificial flowers to track how bumblebee colonies chose between normal sugary nectar and nectar enriched with “quercetin,” a flavonol compound documented for its antimicrobial efficacy against a broad spectrum of Gram-positive and Gram-negative bacteria, as well as fungi and viruses. The colonies were divided into groups as follows:
Over five days of free foraging, colonies exposed to the fungus showed a gradual increase in visits to quercetin-enriched flowers and spent more time feeding on them as the experiment progressed. In contrast, healthy colonies showed no shift in their preferences, and colonies exposed to bacteria also showed no significant change in behavior.
Researchers attributed this difference to the distinct ways each pathogen affects the colony. They explained that chalkbrood disease primarily harms larvae rather than the adult forager bees, suggesting that the increased interest in quercetin by fungus-infected colonies may represent a form of “social medicine,” where workers collect compounds that benefit the brood more than themselves. Conversely, Serratia marcescens bacteria infect adult workers directly, making any potential therapeutic benefit from quercetin less direct, which may explain the absence of a behavioral shift in those colonies.
The researchers concluded that the identity of the pathogen determines the form of behavioral flexibility in foraging for nectar, emphasizing that artificial flowers proved to be a valuable tool for studying the adaptive foraging responses of bees to different pathogens.
