Tropical fish seems able to think ahead, according to researchers

Tuesday, June 15, 2010; HE03

Tropical fish seems able to think ahead

One of the things that makes us human is an ability to think ahead when we interact with someone and adapt our behavior if we expect to encounter that person again. A tiny tropical fish also seems to have this ability, according to new research, behaving more cooperatively with fish it is likely to encounter more often and taking sneaky bites off those it doesn't. The researchers said this was the first time non-humans had been shown to exhibit what economists term the "shadow of the future" behavior, in which people's behavior changes depending on whether they are likely to meet again in the future.

The researchers studied cleaner fish in French Polynesia, so called because they clean other species of fish by eating the parasites from their skin, mouth and gills. This is mutually beneficial behavior, exchanging nutrition for cleansing. But the researchers found that every once in a while, a cleaner fish would take a nip of mucus from the skin of the other fish. That bite inflicts potential harm on the other fish because mucus, while tasty, is also part of the client fish's immune system.

Here's where things get interesting: Cleaner fish only took such bites -- which were visible because the other fish jumped when bitten -- when they were in distant parts of their home range and therefore were unlikely to re-encounter the fish involved. In areas where they often swim, and where re-encounters were more likely, the cleaner fish stuck to the more cooperative behavior of eating only the parasites.

"Our results provide the first evidence supporting the notion that animals may have the ability to flexibly adjust levels of cooperation with individual partners to account for future payoffs," the researchers wrote in the journal Current Biology. The fish "appears to respond to 'the Shadow of the Future' in the same way as humans, by increasing cooperation in situations which have a great probability of future repeated interactions."

"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," said Jenny Oates, a PhD student in the Zoology Department of University of Cambridge, who did the research along with colleagues from the University of Neuchatel in Switzerland.

-- Margaret Shapiro

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