Study explores what happens if you give ants caffeine

By Stephen Beech via SWNS

Ants navigate more efficiently when given energy-drink level doses of caffeine, reveals new research.

The findings could lead to more effective poisons to control invasive insects, say scientists.

Researchers discovered that when ants received a caffeine-laced sugary reward they become more efficient at finding their way back to the reward’s location compared to ants that only received sugar.

Their findings, published in the journal iScience, showed that caffeinated ants moved toward the reward via a more direct path - but did not increase their speed.

It suggests that caffeine improved the ants' ability to learn, say scientists.

The study was conducted on Argentine ants (Linepithema humile), a globally invasive species.

Researchers believe that adding caffeine to ant baits could aid efforts to control them.

Study first author and doctoral researcher Henrique Galante said: “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.

“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, a computational biologist at the University of Regensburg in Germany, explained that Argentine ants are one of the most ecologically harmful and costly invasive species worldwide.

Previous attempts to control them, which focus on using poisonous baits, have proven ineffective, most likely because the ants largely ignored the bait.

The research team wanted to test whether using caffeine, which has been shown to improve learning in honeybees and bumblebees, might improve the ants’ ability to learn the bait location and guide their nestmates back there.

Galante said: “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."

Researchers tested in the lab whether different concentrations of caffeine would impact the ants’ ability to locate and relocate a sugary reward.

The ants walked down a Lego drawbridge onto a testing platform - an A4 sheet of paper overlaying an acrylic surface - on which the researchers had placed a drop of sucrose solution laced with 0, 25 ppm, 250 ppm, or 2,000 ppm of caffeine.

Galante said: “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."

The researchers used an automated tracking system to monitor how fast the ants moved to and from the reward and the directness of their route.

Overall, they tested 142 ants, and each one was tested four times.

The ants were given the chance to offload the food they had collected in between trials.

Researchers also removed and replaced the piece of paper so that the ants wouldn't be able to follow their own pheromone trail back to the reward location.

Without caffeine, the ants didn't learn to navigate to the reward location more quickly on subsequent foraging trips, suggesting that they had not successfully committed its location to memory.

However, ants whose sugary reward contained low or intermediate doses of caffeine became more efficient at relocating the reward.

Foraging time dropped by 28 percent per visit for ants that received 25 ppm of caffeine and by 38 percent per visit for ants that received 250 ppm of caffeine. The effect wasn't seen at the highest caffeine dose.

The researchers showed that caffeine lowered the ants’ foraging times by making them more efficient, not by making them speedier.

There was no effect of caffeine on the ants’ pace at any dosage, but those that received low to intermediate doses of caffeine trips traveled by less tortuous paths.

Galante said: “What we see is that they’re not moving faster, they’re just being more focused on where they’re going."

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

The researchers say they are "optimistic" that caffeine could help efforts to control Argentine ants.

They’re currently testing caffeine-laced baits in a more naturalistic field setting in Spain.