November 13, 2017 14:04 GMT by dailymail.co.uk

Male crabs perform a ‘dance’ after beating rivals

Scientists from the National University of Singapore have suggested that the dance is a way to dissuade competitors from returning.

It's embarrassing enough to lose out to a rival, but male crabs go to the extra effort of rubbing it in their contender's face.

A new study has found that male mangrove crabs perform a victory mating dance after beating out rivals.

The dance serves as a way to discourage the rival from coming back for more, according to the study.

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THE STUDY 

The team set up a combat arena, where randomly paired crabs were put head-to-head in battles.

In total, the researchers analysed 77 battles, scoring the aggression oft eh crabs on a scale of 0 to 3.

Results showed that around 55 per cent of the skirmishes ended with the winner performing a 'dance' – in which the male turned one of its claws downwards, before rubbing the other claw up and down quickly. 

The losing crabs were less likely to return if the winner had performed the dance, with only 35 per cent choosing to try their luck in a second round.

As well as dissuading rivals, the dance was also found to invigorate the winners, and encourage them to become even more aggressive.

The researchers note that performing a victory dance comes at some energy costs to the crab, but that this is a risk worth taking.

 

Previous studies have shown that male mangrove crabs perform the dance after fighting, but the reason for this has remained unknown.

Now, scientists from the National University of Singapore have suggested that the dance is a way to dissuade competitors from returning.

The researchers tested this theory by observing Perisesarma eumolpe – a colourful species of mangrove crab native to southeast Asia.

The team set up a combat arena, where randomly paired crabs were put head-to-head in battles.

In total, the researchers analysed 77 battles, scoring the aggression of the crabs on a scale of 0 to 3.

Results showed that around 55 per cent of the skirmishes ended with the winner performing a 'dance' – in which the male turned one of its claws downwards, before rubbing the other claw up and down quickly. 

The losing crabs were less likely to return if the winner had performed the dance, with only 35 per cent choosing to try their luck in a second round.

The team set up a combat arena, where randomly paired crabs were put head-to-head in battles. Around 55 per cent of the skirmishes ended with the winner performing a 'dance' – in which the male turned one of its claws downwards, before rubbing the other claw up and down quickly (pictured)

The team set up a combat arena, where randomly paired crabs were put head-to-head in battles. Around 55 per cent of the skirmishes ended with the winner performing a 'dance' – in which the male turned one of its claws downwards, before rubbing the other claw up and down quickly (pictured)

In their study, published in Ethology, the researchers, led by Dr Paul Chen, wrote: 'We found losers that experienced victory display performed by winners, presented a decreased instantaneous hazard rate of re-initiating a new fight than losers that did not.' 

As well as dissuading rivals, the dance was also found to invigorate the winners, and encourage them to become even more aggressive.

The researchers note that performing a victory dance comes at some energy costs to the crab, but that this is a risk worth taking.

As well as dissuading rivals, the dance was also found to invigorate the winners, and encourage them to become even more aggressive

As well as dissuading rivals, the dance was also found to invigorate the winners, and encourage them to become even more aggressive

If a crab has already won the battle, using energy up on the dance could ensure a rival gives up.

It could also prevent other crabs nearby from trying their luck.

The researchers added: 'In discouraging losers from restarting a fight, winners reduce the potential costs of a future contest.'

 

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