How male fiddler crabs send females into a sexy swoon

December 30th, 2007 - 2:03 pm ICT by admin  


Washington, Dec 30 (ANI): The sight of a male fiddler crab waving its single giant claw can be a big turn on for a female crab, says a new study.

The study, led by Martin How, a researcher in the Centre for Visual Sciences at The Australian National University in Canberra, has shown that receiver distance affects visual signals in non-human animals: the males wave differently, depending on how close or how far away the female onlooker is.

Like human beings, crabs too change their signal when trying to grab attention, which alters the meaning of the indications.

“I think that the long-range claw-waving signal is essentially saying, ‘I’m a male Uca perplexa and I’m over here! It acts as a beacon towards which receptive females can move, Discovery quoted How, as saying.

How contemplates that the short-range claw waving display is different.

“In this case, the information of the signal changes, and probably says something along the lines of, ‘I’m a big healthy crab with a nice burrow to raise a brood and would make an ideal mate!’” he said.

The researcher explained that the yoo-hoo type wave occurs when the male stretches his large claw to the side, slowly lifts it high above his body and then drops it back to the resting position.

Experiments conducted on a population of mud flat-dwelling fiddler crabs, revealed that the males didn’t stretch out their claws as much when the females were nearby.

When females were right in front of the males, the males really switched strategies by performing a less sweeping wave while lifting their bodies off the ground with their unflexed legs.

How suggested that that’s a macho move for male crabs trying to show off their size to its best advantage.

“Fiddler crabs carry their eyes on long vertical stalks in a fixed position above the body and the eye-stalks always stand upright,” How said.

They “can therefore simplify their visual world into things they see above the horizon and things they see below the horizon.”

“This could be a good thing, though, in that it taps into the anti-predator response of females, causing them to freeze and direct their attention towards the displaying male. But it could also backfire and cause the female to run away, How said.

The study will be published in the journal Animal Behaviour. (ANI)

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