Everything in the flow: Ants provide with various means for unhindered progress. Image: Thinkstock
Read ants Ants do not like traffic jams - he brings their sophisticated supply system to a standstill. British researchers have therefore now observed what the insects do when their supply routes are blocked. Result: They make the affected path less attractive for their conspecifics - without communicating directly with them.

In humans, most things are governed by the top-down principle: one at the top tells his subordinates what to do, and they then pass the information on to their subordinates. However, there are areas that are too complex for such a controller, for example, the processing of large amounts of data or processes where you have to respond flexibly to a variety of factors. Here it would be beneficial if you could fall back on good bottom-up systems, in which all involved independently implement clear rules. Intensive coexistence can lead to organizational patterns of higher orders.

The power of the many

Examples of this can be found above all in nature. Specifically, in the social communities of insects, especially ants. Because they work exactly according to this principle: The behavior of individuals adds up, until the whole group reacts to a changed situation - announcements of a boss or just talking to each other is not necessary. Foraging Example: In ant colonies, there are always a few female workers swarming to seek food for the people. If they find what they are looking for, they mark the route discovered with certain fragrances on the way back. These lure now more conspecifics from the nest and the food source, which in turn leaves even scents. In this way, there is a positive feedback effect - a single signal increases in a short time until it passes the whole group.

But what do the ants do when the way to feed is completely blocked by their reinforcing principle? This question has now been asked by Tomer Czaczkes and his colleagues from the University of Sussex. It is already known that some ant species may leave a kind of stop fragrance mark for such cases, they explain. For example, they prevent their conspecifics from taking wrong turns, and even on less attractive routes, these fragrances are left behind occasionally. display

However, this does not seem to be the only way to respond to unfavorable road conditions, researchers said. They ran ants in the lab across a bridge to a bowl of sugar water and watched how many animals marked the trail as intense. In some cases, the insects ran over a two-centimeter-wide bridge, in others the path was only half a centimeter wide, so that ants moving in either direction touched each other. In addition, the researchers manipulated the number of animals that were on the way - in part by simply leaving no more than nine ants on the bridge, and in part by placing ants-smelling black glass beads on the way To simulate traffic jams.

Negative feedback without compulsion

The result: When there is a traffic jam, the ants leave fewer scent marks on the way. They achieve this in two ways: on the one hand, the individual animals each distribute less fragrance, and on the other, fewer ants feel at all obliged to mark the way. In this way, they achieve a negative feedback effect, explain the researchers: A previously strong signal weakens in this way more and more, thus preventing the congestion in the direction of food sources even worse. However, if the density of the animals on the way decreases again, the signal strength increases again and again a steady flow of traffic will occur.

This shows that ants evidently have a large repertoire of possibilities to react to certain situations, the researchers conclude. In addition to the passive variant of the negative feedback that they have observed in the current study itself, there are still several active variants. These include the already mentioned stop signals as well as the habit of animals to lead others by pushing on a different path than the clogged. This combination of active and passive strategies could potentially serve as a role model for self-organizing systems, the team speculates.

Original work of the researchers:

  • Tomer Czaczkes (University of Sussex, Falmer) et al .: Journal of the Royal Society Interface
Ilka Lehnen-Beyel
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