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News from the University of Regensburg

Ants can predict queues and avoid them

Ants understand if a place is easily crowded just by looking at it - they and use this knowledge to avoid overcrowded food sources in advance, without actually seeing the overcrowding.

22 August 2023

As humans, we are pretty good at working out how busy the cafeteria at work will be, and going elsewhere if we think it will be full. Now, researchers at the University of Regensburg have discovered that ants also understand that some feeding places can get full, and avoid them if they think lots of ants are going there already. 
Queuing is annoying and wastes our time, so we try to avoid it. Imagine if your favorite lunch place was a tiny take-out restaurant, and you saw lots of people coming your way with food from there. If you’re really hungry, you might think ‘oh, it’s probably quite busy, maybe I’ll go somewhere else today’. Ants can have exactly the same problem: they get a lot of their food from insects like aphids which make honeydew. But, small groups of aphids only make a bit of honeydew, and it takes a long time to make more once it’s been eaten. 

Experimental setup. Credit: Credit: ACElab https://www.animal-economics.com/

“Ants are more similar to us than most people think” said Laure-Anne Poissonnier, who led the study. “So, I wondered – would ants also try to avoid food sources they like, if the food sources have limited space and look busy?” To test this, the researchers let ants eat from a special ant feeder, either with holes for lots of ants to feed from, or only enough space for one ant. They then let the ants know that there is another feeder, also easily crowded or not, somewhere else. When the hungry ants came again looking for something to eat, half of them met lots of full ants coming back from the first, favorite feeder, and half met no other ants. If the hungry ants had used feeders with lots of holes last time, or didn’t meet any other ants this time, they just went to their favorite feeder. But, if the hungry ants had used easily-crowded feeders, and met lots of other ants coming back from the favorite feeder, they avoided it, and went instead to the less-favored alternative.  

“The really crazy thing” says Tomer Czaczkes, who also worked on the study “is not even that they avoided the crowded food at rush-hour. That makes sense. The real question is: how did they work out that the feeder could get crowded?”. The ants never saw that feeder before in their lives, and never experienced crowding. Yet, somehow, they worked out that this feeder can only fit a few ants. “This suggests,” adds Laure-Anne “that the ants have a very deep understanding of how the world works”.

Laure-Anne Poissonnier, Yannick Hartmann, Tomer J. Czaczkes (2023), “Ants combine object affordance with latent learning to make efficient foraging decisions.", Proceedings of the National Academy of Sciences (PNAS), DOI: 10.1073/pnas.2302654120


Dr. Tomer J. Czaczkes
Chair of Zoology / Evolutionary Biology
University of Regensburg
Tel.: +49 (0)941/943-2996
Mobil: +49 176 344 27597  
E-Mail: tomer.czaczkes@ur.de 

Dr. Laure-Anne Poissonnier
Chair of Zoology / Evolutionary Biology
University of Regensburg
Tel.: +49 (0)941/943-3356
Mobil: +33 627 43 57 67 
E-Mail: laure-anne.poissonnier@ur.de

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