Nestled just off the east coast of Australia, picturesque North Stradbroke Island is a haven for local wildlife. Yet some of the inhabitants of the island's creeks and swamps are far from peaceful. Slender crayfish are aggressive territorial creatures, explains ecologist Robbie Wilson of the University of Queensland, Australia. When two crayfish catch sight of one another, they size each other up in a ritualistic display, which can quickly escalate from careful tapping of their opponent's chelae (enlarged front claws) to a full-blown fight. Studying these fascinating animals, Wilson discovered that crayfish decide whether to flee or fight based on the size of their adversary's chelae, and that victorious females always have larger and stronger claws. But to his dismay, he found that some males with weaker claws cheat; they defeat stronger foes despite having a weaker albeit larger claw. 'Theory does not predict such dishonesty,' Wilson says. Deceptive signals of weapon strength should not exist, as opponents would quickly stop taking notice of an unreliable cue. Wilson wondered how the crafty males get away with it and publishes his results on Friday 27th February 2009 in The Journal of Experimental Biology at http://jeb/biologists.org.
Teaming up with Candice Bywater, Wilson first took a closer look at the relationship between claw size and strength in female crayfish, to compare them to the males. 'We knew that male signalling is unreliable, so we expected to see more variability in weapon strength in males than in females,' Wilson explains. To measure crayfish claw strength, Frank Seebacher of the University of Sydney, Australia, helped Wilson design a custom-made apparatus consisting of two thin parallel beams with external force transducers. Luckily, it wasn't too tricky to entice the animals to clamp down on the contraption. Crayfish are 'very enthusiastic about biting,' says Wilson. 'We just had t
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The Company of Biologists