Robocrab woos lady fiddlers

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Robotic crab claws have helped uncover just what it is that makes some male fiddler crabs more successful with females than others.

A team of scientists from the Australian National University in Canberra, led by Dr. Sophie Callander, designed and built a series of life-like robotic crab arms topped with brightly coloured claws to simulate the waving displays of Uca mjoebergi, a species of fiddler crab found on the exposed mud flats of Northern Australia.

The researchers then spent many hours trying various combinations of claw size and wave speeds to see just what it was that caught the female's eye.

It was found that unsurprisingly females responded to the robotic arms with the biggest claws that waved the fastest; suggesting that males with these characteristics are considered good potential mates as it shows they must be strong and healthy to be able to grow and fuel the waving of such a cumbersome claw.

However the team also noticed that robocrab's success rate with the ladies was increased further if he was flanked by two smaller clawed, slower moving arms.

This insight has potentially helped clear up the mystery of why large males have been observed rushing to the aid of smaller neighbours when another larger male tries to steal their mud burrow. It now seems rather than being an act of selfless kindness it's all because hanging out with puny-pincered males makes them look more impressive to the females, increasing their chance of passing on their genes to the next fiddler generation.

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