The migration of baby land crabs inland from the sea is a natural, cyclical occurrence, but residents in Cayman Brac report this year’s influx is bigger than ever.
The crabs, nicknamed “Hurricane Crabs” because of a superstition that they are portents of a bad hurricane season, have been spotted covering roads and crawling up buildings throughout the Brac in recent days.
District Commissioner of Cayman Brac Ernie Scott said there were “hundreds of thousands of the little critters” and that when they appear, they usually stick around for about two weeks.
“There’s a very strong feeling on the island that they relate to the arrival of a hurricane,” said Mr. Scott, but he added: “I’ve seen them here in hurricane seasons when we didn’t have any hurricanes and I’ve seen them in a season where we’ve experienced hurricanes.”
Their appearance this early in the season and in such large numbers may be due to the baby crabs being able to get out of the water and onto land earlier than usual and more of them surviving due to the ocean currents and the recent “supermoon”.
Tim Austin, deputy director of the Cayman Islands Department of Environment, said the tiny red crabs are most likely baby red land crabs that were hatched a few weeks ago.
“We have three species of land crab here that have a pelagic lifestyle. Crabs originally came from the sea and they have evolved to live on land but they have to spawn in the sea,” Mr. Austin said.
That’s why, every year, large numbers of land crabs are seen migrating from land, across roads and gardens, to the sea – usually once the rainy season begins.
Because of heavy rains in recent weeks, the crabs have already made their trek to the water’s edge, where they lay their eggs. “The eggs hatch in the sea and they live there for a couple of weeks as larvae until they grow to a stage when they look more like crabs and they make their way back to shore,” Mr. Austin said.
However, that journey back to land is not easy and the tiny crabs’ survival depends on the whims of the currents. Although the crabs lay eggs and hatch each year, some years the baby crabs do not manage to make it back to shore.
Due to the large full moon this month, known as a “supermoon” because the moon was brighter and closer to the Earth than any other time of the year, the tides were low, so the larvae and little crabs would not have been washed out to sea and may have had an easier journey than usual to get back to land, Mr. Austin said.
And because the sea’s currents effectively corral the larvae and crabs, huge numbers of them can show up at once as they are carried back to land by the same current, he said.
He also does not discount the old-time belief that the mass arrival of the crabs may have something to do with hurricanes.
“The hurricane connection is interesting … No one’s really looked into it, but it’s not completely impossible.
If you think about the fact that ocean currents are responsible for hurricanes and that they influence the crabs coming back to shore, it’s not impossible that there’s a relationship, but as to what that relationship actually is, I’ve no idea,” he said.