When ants eat or drink caffeine, many interesting things happen

Ants march across sidewalks and kitchen counters as if they own the place. They cross oceans inside cargo ships, set up vast super-colonies, and push out native species on six continents.

Once a nest of ants settles in, homeowners and farmers often reach for poison baits, yet the insects lose interest before enough of them carry the toxic treat back home.

A new study suggests that a tiny splash of caffeine could keep the party going – and give pest managers an edge.

The research shows that moderate doses of caffeine sharpen an ant’s memory for the bait’s location. Ants that sipped a caffeinated sugar drop found it again more quickly on later trips, leaving a stronger scent trail for nest-mates.

The discovery points to a low-cost tweak that might finally turn the invader’s own teamwork against it.

Tiny ant, huge impact

The Argentine ant (Linepithema humile) is only about one-tenth of an inch long, yet its cooperative spirit builds super-colonies stretching thousands of miles along the Mediterranean coast and the U.S. West Coast.

Those armies displace local insects, rob hummingbird feeders, and even short-circuit electrical gear.

Recent economic analyses peg the global cost of invasive ants – including crop losses and control bills – at billions of dollars each year. No wonder pest crews keep searching for smarter tactics.

Giving caffeine to ants

To find out, researchers set up a miniature arena: a Lego drawbridge led each ant onto a letter-size acrylic platform where a single sugar drop waited.

Some drops carried no additive, while others contained 25 parts per million (ppm), 250 ppm, or 2 000 ppm of caffeine. One hundred forty-two ants took part, and each explorer tackled the course four times.

“The idea with this project was to find some cognitive way of getting the ants to consume more of the poisonous baits we put in the field,” says the study’s first author Henrique Galante, a computational biologist at the University of Regensburg.

Automated cameras tracked every step, logging travel time and the straightness of each path. Without caffeine, the insects wandered, needing the same span to reach the treat on every attempt. Add a modest stimulant, and the story changed.

Caffeine gives ant focus, not speed

“We found that intermediate doses of caffeine actually boost learning – when you give them a bit of caffeine, it pushes them into having straighter paths and being able to reach the reward faster,” Galante explained.

In fact, ants that tasted 25 ppm caffeine shaved 28 percent off their foraging time on every return. Those on 250 ppm cut the clock by 38 percent.

Picture an individual that spent 300 seconds during its first outing – it would need just 113 seconds after three more trips on the lower dose and 54 seconds on the medium dose.

The stimulant did not act like an energy drink. There was no uptick in raw speed. “What we see is that they’re not moving faster, they’re just being more focused on where they’re going,” Galante noted.

“This suggests that they know where they want to go, therefore, they have learned the locations of the reward.”

Only path geometry tightened; pace stayed the same. At the heaviest 2 000 ppm dose – the level that kills half of honeybees in tests – the learning advantage disappeared.

Sharper trails, deadlier bait

Argentine ants rely on pheromone highways. A worker that discovers food drags its stinger along the ground, laying a chemical breadcrumb trail that guides the next shift. Faster relearning multiplies that effect.

“We’re trying to make them better at finding these baits, because the faster they go and come back to them, the more pheromone trails they lay, the more ants will come, and, therefore, the faster they will spread the poison in the colony before they realize it’s poison,” Galante continued.

Adding caffeine could also slash the waste that now limits bait stations. In neighborhoods and orchards, technicians often replenish gels every few days because the first wave of foragers gives up.

A caffeinated lure might stay attractive long enough for queens and larvae to receive a lethal serving.

What happens next

The team is already field-testing the recipe at infested sites in Spain. They also plan to check whether caffeine interacts with common active ingredients such as hydramethylnon or spinosad.

“The lowest dose we used is what you find in natural plants, the intermediate dose is similar to what you would find in some energy drinks, and the highest amount is set to be the LD50 of bees – where half the bees fed this dose die – so it’s likely to be quite toxic for them,” Galante notes.

Selecting a concentration that boosts memory without harming pollinators will be crucial.

Caffeine’s appeal extends beyond Argentine ants. Other invasive species – including fire ants and big-headed ants – share the same food-sharing habits that make baiting tricky.

If the stimulant nudges their neural circuits in a similar way, managers could deploy a single additive across multiple pest fronts.

What we learned about ants and caffeine

To sum it all up, caffeine improves ants’ overall focus and learning without increasing speed, allowing them to navigate straighter paths and lay stronger pheromone trails.

This effect boosts the effectiveness of bait traps, leading more ants to the poison and increasing the chances of it spreading through the colony.

However, the benefit peaks at moderate doses – very high levels eliminate the learning advantage and can be toxic. So, overall, caffeine makes ants better at foraging and sharing, which ironically makes them more vulnerable to well-designed pest control strategies.

For now, the message is simple: a dash of coffee in the buffet may turn an army’s fabled navigation skills against itself. When the ants get better at remembering dessert, the colony’s days could finally be numbered.

The full study was published in the journal iScience.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–