Check your shoes! Why crabs are appearing in odd places

CAIRNS northern beaches residents are being urged to check their shoes before slipping them on, with toe-pinching crabs in a breeding frenzy.

White-clawed mangrove crabs (Tiomanium indicum ) have been spotted scuttling across suburban yards and roads at Holloways Beach after the weekend's major rainfall.

The city received a total 336mm of rainfall since Saturday after about three weeks of humid, dry conditions.

A white-clawed mangrove crab (Tiomanium indicum) spotted in a yard at Holloways Beach. Photo: Daniel Bateman
A white-clawed mangrove crab (Tiomanium indicum) spotted in a yard at Holloways Beach. Photo: Daniel Bateman

The dark purple and white-coloured crabs - resembling juvenile mud crabs - are considered rare, as they are not commonly seen outside the suburbs of Trinity Beach, Trinity Park, Yorkeys Knob and Holloways Beach.

The crabs' mini-migration into local estuaries has been spurred on by a combination of heavy rainfall, humidity, moon phases and tides, according to Queensland Museum crustacean expert Dr Peter Davie, who has been receiving reports of the randy crustaceans from the area for the past five years.

"What I imagine has happened is there's been a very successful larval landing a few years ago, increasingly," he said.

"What might have happened is these crabs might have let go a whole lot of eggs and the larvae have all sort of landed in and around Holloways altogether in quite some numbers and managed to survive each year.

"And because there's more of them living there, the chances of the larvae coming back is getting higher and higher, so the population is building."

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A "land crab" (Tiomanium indicum) found in a backyard at Holloways Beach. Photo: Tracey Schneider

Last year, one of the crabs made local headlines after a Holloways resident discovered it had found its way into his work boot, inside his home, pinching his toe as he went to put on his shoe.

Dr Davie urged residents not only to check their shoes, but be vigilant for the small crabs while the short-lived migration continued for the next few days.

"They're (aggressive) because they're out migrating and they've got a purpose," he said.

Live crab found in Mick Taranto's work boot, Holloways Beach
Live crab found in Mick Taranto's work boot, Holloways Beach

He said the crabs' population would never reach the migratory numbers experienced on Christmas Island each year.

"They're constrained by the habitat, and they're not truly terrestrial crabs, unlike Christmas Island," Dr Davie said.