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Crayfish Remember Before a Rematch
Yet another example of society's underestimation of another species.

The New York Times, Observatory, Henry Fountain, July 24, 2007

Crayfish may be small, but they aren't stupid. After losing a fight they can remember who beat them, and may use that information to steer clear of another fight against the same opponent.

Australian researchers studied fights between males of an aggressive species of freshwater crayfish, Cherax dispar. Like most crayfish, C. dispar fights by locking claws with its opponent and holding on until one creature gives up and slinks away.

The crayfish with the stronger claws almost always wins a first fight and, in subsequent fights with the same crayfish, it keeps winning, The loser often slinks away without even fighting. The researchers, Frank Seebacher of the University of Sydney and Robbie S. Wilson of the University of Queensland, wanted to see whether in those subsequent fights the loser just blindly leaped into the fray again or recognized that it was up against a superior opponent.

In their experiments, described in Biology Letters, they disabled the claws of the winner of the first fight by supergluing them shut and let the two crayfish go at each other a half-hour later and 24 hours later. Even with its claws disabled, the winner of the first fight kept winning, indicating that the loser somehow remembered that the winner was stronger.

This "winner effect" is not unknown, but the researchers say it seldom persists as long as 24 hours. They suggest that it may be advantageous for a crayfish to remember how it fared in a previous fight -- to avoid additional fights, which are costly in terms of energy use, not to mention potential injuries.

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