Angry Cuban land crab.
Photo Grace Willan

They dwell in Cuban forests and flock to the sea for sex

Saga of the Cuban land crab

Hundreds of millions of Cuban land crabs sleep in cool, moist forest holes during the day. They scavenge the jungles at night in search of rotting leaves and other detritus for dinner.

Introducing Grejo, the logo of Jazz Cuba tours

Logo of Havana Jazz Festival tours.

Meet Grejo, pronounced grey-ho. He’s a Cuban land crab and our Jazz Cuba logo. We like him because he and his ilk are plucky little devils – animated and lively – like the Cuban music and dance tours we organize. He moves horizontally in edgy moonwalk way. And his kind comes in many colors, just like Cubans.

Grejo (his moniker derives from cangrejo, the Spanish word for crab) and his multitude thrive in untold millions in Cuba, and on other islands of the Caribbean.

His genus, Gecarcinus ruricola, is a species of terrestrial crab. Common names include the purple, black, red, or yellow land crab, and sometimes zombie crab (because they raise their claws defiantly when confronted by cars and predators).

The life of Cuban land crab is an utterly fascinating natural history tale. Read on.

Land crabs smashed by cars in Cuba.
Crunch, crackle, squish. They never stop, no matter what the adversity, an invisible drive compels them to the sea to spawn. Photo unknown.
Each spring, millions of small reddish land crabs emerge from the moist forests surrounding Cuba’s coastlines to breed in the nearby sea. The annual invasions – which last for weeks – wreak havoc on coastal communities. Roads are covered with smelly smashed crabs and tires are shredded by their sharp shells.

The crabs and their eggs provide a feast for birds, fish, and other hungry mammals. Yet, seafood-loving Cubans rarely eat them, as it is said they contain a harmful toxin.

Cuban Crab Hawk eats Cuban land crab.
Cuban Crab Hawk devours smashed land crab. Crab carcasses are a favorite snack for vultures, hawks, and dogs. Photo Shane Jones.
More than four million years ago, the ancestor of these crabs – known to scientists as Gecarcoidea – lived in the sea. Slowly, they evolved to survive in a foreign place: the shaded forest floor. However, like marine crabs, land crabs still breathe with gills that must remain moist. To stay damp, the crabs dig tunnels. During the spring rains, males and females seek each other out and mate.

A few weeks later, the female crabs, swollen with eggs carried in a pouch, head for the nearby sea. The journey, which may be as long as six miles, can take days. And there are plenty of obstacles, such as roads, curbs, and even coastal resort swimming pools. On sunny days, the crabs must find shade – or dehydrate and die.

Those that reach the sea face one last challenge – laying their eggs while avoiding being swept back into the water. These crabs are land creatures and cannot survive in the sea. Once the ripe eggs are deposited in the sea, they hatch immediately. After a few weeks, the baby crabs climb back onto land and head for the forests, to begin the cycle anew.

Officials make efforts to protect the crabs by closing some roads and sidewalks to create “crab crossings.” In part, that’s because the great crab migrations have become a macabre tourist draw. For some people, a glimpse of thousands of crabs scrambling into the surf is an unforgettable spectacle.

The life, death, and sexual habits of Cuban land crabs

Cuban land crab seeks shelter beneath rocks.
Cuban land crab finds reprieve from tropical sun and predators in rocky outcrops.

They grow one inch a year, mature in five, and live up to ten. They are nocturnal. They have a nephritic pad onto which they urinate. Microbes cleanse the pee then the precious moisture is reabsorbed. They can live many miles from the sea, and at high altitudes, but must return to the ocean to breed. They move swiftly, up to two yards a second.

Until age three, young crabs live in burrows dug by their elders and eat food brought to them by adults. They are omnivorous scavengers and dine on dead plant and animal droppings. A female lays around 85,000 eggs. Cars and trucks squish tens of thousands of land crabs when they cross roads during the annual mating march to the sea. Crab roadkill is a favorite snack for vultures, hawks, and dogs – all of which have better road sense.

Video: Cuban cars create catastrophe for crabs

Swarming Cuban land crabs. Witness the many obstacles land crabs overcome to complete their annual mating migration to the sea. Two minutes, 11 seconds.