This image shows L. humile before and after drinking caffeine.
Ants that receive a dose of caffeine similar to that found in energy drinks, along with a sweet reward, navigate more intelligently.
In a new study, scientists demonstrated how caffeine affects ants and their ability to learn. Specifically their efficiency in reaching food.
The main focus was on how different concentrations of caffeine would impact the ants’ ability to locate and relocate a sugary reward. A not-so-small group of 142 Argentine ants received three different doses of caffeine.
Argentine ants are a global invasive species. That is why a study like this is significant for the contributions it can make to their control. A new study showed that it is caffeine that could help control ants through bait.
By tracking the ants’ movements on an A4 sheet of paper overlaying an acrylic surface they tried to get the answer. On the platform, they made a drop of sucrose solution with 0, 25 ppm, 250 ppm, or 2000 ppm of caffeine.
“Caffeine concentrations were chosen based on previous reports of their effects on Hymenopterans. The idea was to choose a wide range (from natural to likely to be toxic) to try and pick up on potential dose-dependent effects,” explained Henrique Galante, the first author and a computational biologist at the University of Regensburg, for Interesting Engineering (IE).
The first is the one that can be found in natural plants. The middle dose is similar to that found in energy drinks. And the third, the highest dose is the LD50, which has been shown to be toxic to bees.
Without caffeine, the ants did not learn to get to the place with the reward faster. Meaning they did not successfully remember its location. However, ants who were given a sweet reward with low or medium doses of caffeine became more efficient at finding the reward.
Search time decreased by 28% per visit for ants given 25 ppm caffeine and by 38% per visit for ants given 250 ppm caffeine. In terms of time, this means that if the ant took 300 seconds for the first case.
For the last attempt, it would take 113 seconds. While he only needed 54 seconds with the medium dose. At the third dose, this effect was absent.
Caffeine reduces time by making them more efficient but not fast. This means that they know where they are going, that is, they know the location where the prize is.
When questioned about gender differences in ant behavior, the researcher clarified that their experiments exclusively involve worker ants, which in the case of L. humile are all female and genetically similar. Consequently, gender distinctions are irrelevant in their studies.
”We give each ant four test visits because this experiment is quite hard for them. We wanted to give them enough time to learn the location of the food. Simultaneously, each visit can take up to 20 minutes, so too many visits also becomes impractical,” he said.
“We have previously shown that these ants are strong and fast learners with 1-2 visits being enough to see an effect. Hence why we used 4, to make sure we don’t lose any potential effects,” Galante further added.
There is no reported successful eradication of Argentine ants, despite many attempts.
“In this work, we show that caffeine reduces foraging time. Thus it is expected that by adding a small amount of this cheap widely available chemical to the baits, ants will have a faster initial recruitment, and thus consumption, of the toxicant before they eventually perceive it and/or abandon these baits,” said Galante.
He expressed a profound fascination with the implications of their research, indicating that caffeine may selectively influence distinct navigational mechanisms, thereby impacting different brain regions.
“Because we weren’t necessarily looking for that, our experiment does not allow us to fully disentangle different navigation mechanisms as they are all “active” simultaneous,” he concluded.
The study was published in the journal iScience.
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Maria Bolevich Maria Bolevich graduated from Medical High School and Faculty of Metallurgy and Technology, Department of Environmental protection. She is an environmental protection engineer, and she wrote her first scientific article as a student in 2009 which triggered her passion for science journalism. As a science, health, and environmental journalist she has been collaborating with many international media, including Nature, SciDev… She is a recipient of a number of noteworthy awards in her field of expertise.
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