Archer fish never look back

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Even the best baseball players dither more than an archer fish.

An archerfish fires water at an insect overhead Credit: © badmanstropicalfish.com

Archer fish are better than the best baseball players at predicting where plummeting prey will land, suggests a new study. They need only one glance.

The fish (Toxotes jaculatrix) shoot water jets from their mouths at insects perched overhead. After a hit, they have to guess where their lunch will land, and get to it before it's gobbled by fellow fish.

"It's very important for them to be quick," says Stefan Schuster of Albert Ludwigs University in Freiburg, Germany. He took high-speed videos of the fish and found it takes them just a tenth of a second to judge when and where in the water their food will fall. They then flip towards their target and swim there without looking back1.

Humans catching a ball thrown from far off, as in baseball or cricket, don't make just one prediction on where best to stand to secure the match-winning catch. We look repeatedly at the ball to alter our steps, which usually take a curved path.

It is not clear whether the fish calculate each trajectory from scratch, or whether they take a best guess based on previous triumphs. "I expect experience plays a large role," says Schuster, who now plans to look into this.

Hoverflies use similar predictions to intercept other flies when mating, says Thomas Collett of Sussex University, UK, who blew peas at them with a peashooter to study how they set a collision course.

But hoverflies have a fairly standard size and speed. Archer fish shoot prey of a variety of sizes that fall at different speeds. This makes their decisions far more complex. "This mechanism varies a lot in different species," says Collett.

References

  1. 1

    Rossel, S., Corlija, J. & Schuster, S. Predicting three-dimensional target motion: how archer fish determine where to catch their dislodged prey. Journal of Experimental Biology, (in the press), (2002).

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Westney, C. Archer fish never look back. Nature (2002) doi:10.1038/news020923-15

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