Neuchâtel expat scientists discover fish just like us

Tropical fish change their behaviour like humans as they interact with others, an expat team of biologists at the University of Neuchâtel has discovered.

After a three-year project with colleagues from the University of Cambridge, the scientists found that cleaner fish, known technically as “labroides bicolour”, adapt their acts with regard to the future, a human type of behaviour that has never been observed in animals before.

Redouan Bshary, a professor of behavioural ecology at Neuchâtel, was among those involved in making the discovery and is one of the authors of the findings, published this week by Current Biology, a scientific journal.

“I have spent the last 10 years showing fish are at least not as stupid as we think,” professor Redouan Bshary told Swisster with a laugh.

“I did not expect we would be able to test this,” Bshary said.

“It is possible that other animals show flexible behaviour adapted to the future, the thing is that is it really difficult to design experiments to prove it,” he said.

Bshary joined fellow scientists Jenny Oates and Andrea Manica from Cambridge University in the project.

This involved ocean dives in southeast Asia, where bicolour cleaner fish live in coral reefs.

As their name suggests, they remove parasites from the skin, mouths and gills of other fish, called "client species".

However, cleaner fish sometimes cheat by taking a sneaky bite of mucous from client species, which is the slimy surface that protects skin from infection.

Removing parasites is cooperative behaviour, benefiting both species, while eating mucous is potentially harmful to other fish, which jump when this happens.

Thanks to this signal, Jenny Oates a doctoral student at the University of Neuchâtel observed that the cleaner fish deceived client species less often when they were in the core area of their home range, where they spent more time, and where they were more likely to meet the same client species again.

"The results suggest that, like humans, cleaner fish are able to take account of the future rather than just the immediate consequences of their actions," Oates said.

To conduct the experiment, she dived and followed the 13-centimetre fish at a three- to five-meter distance in their natural environment.

The sly cleaner fish are more likely to cheat in their interaction with other species when they are away from their core area, as they are less likely to meet the same fish again.

If one cannot say the tropical fish are clever, they show an unexpected adaptation of their actions regarding to consequences, the scientists concluded.

With this species of cleaner fish, the chance was they live in a wide home range and show distinct behaviour in the favourite area of their territory and outside of it.

However, the reason for the distinct behaviour cannot be explained by the fact that individual fish would recognize each other.

This seems very unlikely as cleaner fish can have over 2,000 interactions a day.

Meanwhile, in the core area where they spend a lot of time, cleaner fish are likely to remove parasites from the same client at a 20-minute interval.

In such cases it is not known whether they can remember each other.

“Anyway, the possibility is that after having been bitten, a client fish may keep away from all cleaner fish,” said Bshary.

That is why bicolour cleaner fish avoid tricking their partners in their core area.

Otherwise the client fish would stay away in the future, leaving the cleaner fish with fewer parasites to eat.

Researchers now plan to bring the fish to a laboratory at the University of Neuchâtel’s Institute of Behavioural Ecology to make further tests to build on their discovery.