Biologist spots ‘crab horde’ near Australian coast

It’s a sight that will make you either recoil in horror or drool out of hunger.

Maine biologist Sheree Marris has filmed a massive gathering of spider crabs in Port Phillip Bay, off the coast of Australia. She made sure it was sufficiently epic:

“Who would have thought something like this, that is so spectacular, could be happening in Australia on the southern shore,” Marris told BBC News.

Scientists are currently trying to figure out why the crustaceans gather en masse inside the bay and elsewhere around the world. Some experts suspect it may be related to molting season, when the crabs shed their old protective shell in order to grow larger. The crabs are highly vulnerable into a new shell develops and the massive horde may be an effective means of thwarting attacks by predators.

“People think Port Phillip Bay’s a marine wasteland … but this is really unique and it’s really spectacular,” Marris said. “Not only is [Melbourne] the most livable city above the water, it is also the most livable below the water.”

The entire continent and waters around Australia is one massive biodiversity hotspot, with 30 marine mammals and 1,500 species of fish inhabiting just the Great Barrier Reef.

Spider crabs, which are eaten by octupuses, cormorants and other predators, crawl slowly and have long, thin pincers, which are fairly weak compared to those of other crabs.

Redorbit actually reported on one of the previous times this happened, back in 2005. A decade ago, about 50,000 crabs were said to have participated in the gathering. The crabs were said to be more than 3 feet deep in places, and piled 10 high.

“It was like something out of a science-fiction movie… as far as you could see there were crabs,” said Museum Victoria scientist Mark Norman at the time, adding that the crustaceans were “scaring the hell out of local fish.”

“We got some earlier warning from divers that they were here en masse, but we had no idea it was going to be so big,” he added. “This has been observed elsewhere in the world, like the Mediterranean … it’s not a rare event, but it’s rare that you encounter it.”

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Image credit: Sheree Marris

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