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Attracting True Love: Crabs Show How It’s Done January 15, 2008

Posted by Mrs Weird Scientist in Animals, Think About It.
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Fiddler Crab

Credit: Martin How, ANU. A fiddler crab prepares to captivate his true love!

When it comes to love, you might be surprised to learn that crabs have some similar behaviours to humans. A study led by Martin How from the Australian National University (ANU) has found that crabs change their behaviour depending on the distance between them and their true love. The full study results can be seen in the journal Animal Behaviour.

Meet The Fiddler Crabs

Fiddler Crab - waving claw Credit: Martin How, ANU. A male fiddler crab does some charming claw-waving to get the attention of a female fiddler crab. Hmmm. I wonder if the lady crab will approach!

Fiddler crabs – formally known as Uca perplexa – are tiny crabs that reside on mudflats near North Queensland, Australia. Observation of the fiddler crabs showed some interesting behaviour. How spent two weeks observing and filming the fiddler crabs. Think about how humans try to get attention from someone they like. Sometimes – if the person is far away – they might wave their hand to catch that person’s attention. The fiddler crabs have a similar way of communicating. A fiddler crab will wave his large, colorful claw! According to How:

We know that in everyday life, attracting the attention of a distant person involves gestures and vocalisations different from those used when that person is nearby.

The crab’s behaviour gets even more specific. When the female crab moves closer, the male crab changes the movements of his claw. How explains:

Over distance he uses these very flamboyant, very conspicuous claw-waving displays, ‘I’m over here come and see me.’ When the female approaches very close, he adjusts those displays so they are less broad and flamboyant and more coaxing.

So basically, the male crab has to make some obvious gestures to get the female crab’s attention. Once he has that attention, however, he can be more subtle.

Fiddler Crab 3

Credit: Martin How, ANU. A fiddler crab shows off his moves – he waves his brightly colored claw to impress the female crab.

Crabs Like To Show Off

Not only do the male crabs have this interesting array of behaviours to gain attention from the female, but they also like to do some showing-off as well! This showing-off includes raising his body off the ground, performing some brag-worthy unflexed leg lifts and of course – the grand finale – the slow claw lift. How suggests that this is the male crab’s way of showing off his special qualities in hopes of convincing the female to follow him into his burrow to mate.

So really, the study tells us that whether it’s crabs or humans, animals use all sorts of special tricks and gestures to attract a mate. If only I had a colorful claw to wave when I wanted to get someone’s attention! I suppose I will have to make do with painting my fingernails.

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1. Marvin Light - February 3, 2009

How long does this ritual last?. This is the first sight I saw that actually saw that talks about the mating of crabs.

Thank you

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