'I'm having nightmares tonight': Swarm of spider crabs rip an octopus apart as thousands of them descend on the waters near Melbourne

  • Annual migration of spider crabs has arrived in coastal waters of Port Phillip Bay 
  • Thousands of the creatures migrate to moult their shells in the shallower water
  • Terrifying footage has emerged of several crabs ripping apart an octopus
  • Images of the migration have caused horrified reactions on social media 

By Chris Pleasance For Daily Mail Australia

Published: | Updated:

It could be a scene from a zombie movie - an innocent animal ripped to shreds by a mindless hoard with a taste for flesh.

In fact this is horrifying footage taken in the waters of Port Phillip Bay, near Melbourne, where the annual spider crab migration is underway.

Diver Chiharu Shimowada captured the moment several crabs ripped an octopus limb from limb from limb...

This is the terrifying moment a swarm of spider crabs was captured ripping an octopus limb from limb during a migration near Melbourne

This is the terrifying moment a swarm of spider crabs was captured ripping an octopus limb from limb during a migration near Melbourne

Mr Shimowanda, who has been diving for 10 years, said he has never seen anything like the migration before.

The event is well-known in the Melbourne diving community, he said, but usually does not occur until May or June.

He said: 'The crabs stay (in the) very shallow waters, so anyone can go and see this amazing event.'

Nobody knows exactly why the crabs migrate to the shallower waters, or why the usually solitary animals come together to form a massive swarm.

Up to 100,000 spider crabs gather in the shallow waters near Port Phillip during autumn in order to moult their old shells and grow new ones

Up to 100,000 spider crabs gather in the shallow waters near Port Phillip during autumn in order to moult their old shells and grow new ones

Nobody knows why the usually solitary crabs migrate en-masse, but it is thought they rely on safety in numbers while moulting as they are vulnerable to predators

Nobody knows why the usually solitary crabs migrate en-masse, but it is thought they rely on safety in numbers while moulting as they are vulnerable to predators

Because the migration coincides with the time in their life cycle when they moult their old shell for a new, larger one, many believe they are acting on the principal of safety in numbers.

After moulting, the crabs are very soft until they form a new shell, making them vulnerable to rays, sharks and other animals who prey on them.

Staying together in a large group reduces the chance that any one individual will be eaten, scientists say, while moving to shallower waters means some of their larger predators cannot reach them.

Writing about the migration on Twitter, Ashling Xo said: 'Just seen the spider crab... Yep I'm definitely having nightmares tonight!'

Pat David added: 'Ah, sleep is for the brave. I know what's terrifying my dreams tonight!' 

Melbourne

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