Can bees self-medicate with alcohol?

We picture honeybees as tireless workers, buzzing from flower to flower in search of nectar. But what happens when they fall ill? Could they, like us, seek out something in their environment that helps them feel better? Our new research, just published in Behavioral Ecology, suggests that honeybees might "medicate" with alcohol.

One of the biggest threats to honeybee health is a microscopic gut parasite, Nosema ceranae. Once inside a bee, this parasite attacks the cells lining the gut, disrupts nutrient absorption, drains the bee’s energy, and shortens its lifespan. It’s a major problem for bees worldwide.

Ethanol, the type of alcohol found in wine and beer, might seem like a strange thing for a bee to consume. But in nature, it actually seems quite common. Many flowers naturally contain tiny amounts of ethanol in their nectar, produced by microorganisms that ferment the sugars. It’s usually in very low concentrations, but bees can encounter it when they forage.

To test whether bees change their behavior when infected with Nosema, we offered groups of healthy and infected bees a choice between plain sugar water and sugar water with a low dose of ethanol (either 0.5% or 1%). We found that infected bees preferred the ethanol-spiked food, and that their increased ethanol intake was linked to improved survival. Although the parasite levels didn't change, meaning the alcohol didn’t directly kill the parasite, it still helped the bees survive the infection.

To experimentally infect bees with Nosema, we typically offer individuals in Petri dishes a precisely measured droplet of spores dissolved in sugar water. Here, a bee is shown consuming such a droplet. This method is less stressful for the bees and much easier to implement than alternative procedures. Video credit: K. Miler

The idea that animals can self-medicate isn’t new. Monkeys, or even caterpillars and fruit flies, have been observed eating medicinal plants or substances when sick. What we found here fits many of the criteria for self-medication: the bees choose to consume ethanol, it seems to improve their survival when sick, and it's potentially harmful to healthy individuals. But it’s unclear how ethanol works. Potentially, it can help bees cope with stress or infection by affecting their metabolism or immune system, or altering the gut environment in a way that makes it harder for the parasite to thrive.

Our study doesn’t suggest we should start feeding alcohol to bees. But it reveals that bees may be capable of changing their behavior in subtle, adaptive ways when they're sick. That’s a level of flexibility and complexity we don’t usually associate with insects. The study also adds a new piece to the puzzle of bee health. With parasites, pesticides, and poor nutrition all threatening pollinators, understanding how bees interact with the natural substances in their environment could help us protect them.

Check out our publication here, and stay tuned for follow-up studies!