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In the UK, over the weekend of 6-7 August 2022, thousands of spider crabs appeared close to the shore in St Ives, Cornwall.<\/p>\n
Common spider crabs, also known as spiny spider crabs (Maja brachydactyla<\/em>), live along the East Atlantic coast from the British Isles in the north to West Africa in the south.<\/p>\n They are large, orange-coloured crustaceans, with long, spindly spider-like legs. They are often covered in algae, sponges and other bits and bobs, giving them a slightly fluffy look.<\/p>\n Juvenile spider crabs live in the shallows, before moving offshore into deeper water as adults. They can be found on rocky, sandy or muddy substrates to a depth of more than 100 metres.<\/p>\n Find out more about crabs:<\/strong><\/p>\n Mature crabs will undertake a summer migration into shallower waters in order to moult their tough exoskeletons. During these migrations, they can be seen in huge accumulations of thousands of individual crabs.<\/p>\n It is believed that this strategy allows for \u2018safety in numbers\u2019. The crabs on the outside of the gatherings still have their tough shells, while the crabs on the inside have softer shells from just starting or finishing their moulting. The texture of the crab at this time is a bit like a hard-boiled egg, making them particularly vulnerable to predators. It is also at this point that the males will grab the opportunity to mate with the still-soft females.<\/p>\n It was one of these enormous gatherings that was witnessed in Cornwall, just metres from the beach.<\/p>\n