Green Pages

The Crustacean Invasion

crab-dionGreat Blue land crabs are a tasty terror!

Story & Photos By B. Naqqi Manco, Sr. Conservation Officer, Turks & Caicos National Trust

They come every year. The spring rains awaken them and the Islands are subject to the onslaught of a creepy crustacean invasion. Most welcome these creatures, but I’m still working on feeling anything but pure terror.

This invasion is the spring emergence of the Great Blue land crabs from their dry season burrows. The Great Blue land crabs (Cardisoma guanhumi) are well known to the inhabitants of the less populated islands of Middle and North Caicos, though can be just as familiar on the more populated islands of Providenciales and Grand Turk.

Most visitors to the Turks & Caicos Islands never have the privilege of meeting a Great Blue land crab. They’re not common on the most populated islands because of the culinary fondness that the people of the Turks & Caicos Islands have for them, and the development that has filled in the low-lying areas they need to live. Whether in the traditional seasonal favourite crab ‘n’ rice, minced in salad, fried in cakes or stewed into crab-soup ‘n’ dumplings, the emergence of the crabs with the beginning of the rainy season figures prominently into the menus – and pocketbooks – of many island people. Due to extensive development and thorough hunting on Providenciales, they are not especially common there now, though there are still plenty around in remote areas. But in Middle and North Caicos, where there are fewer people and a lot more bush where crabs can live and eat, they are commonly met on warm, moist nights from May to September.

Met all too commonly for my tastes. I’ll expose my emotions upfront so that it is understood that I am by no means an unbiased author on this subject. I do not like land crabs. Why? It isn’t just because their claws are insanely dangerous and could remove a toe. It isn’t just because they look like mechanical robot spiders from Hell. It’s mainly because they are terribly destructive to gardens. They eat seedling vegetables in my plot. They ravage my bok choy patch and overturn my potted plants.

Still, as wild animals, they intrigue me. What were these crabs, which look like clockwork nightmares, doing several miles inland in my backyard? Shouldn’t crabs be at the bottom of the sea, where they can neither be seen by me nor upset my vegetable patch? Also, I often wondered where these huge crabs “went” after September, when they seem to disappear, aside from the odd stray crab that is seen on the road after unseasonably heavy rains in the dry times. Their habits interested me. So I set out to learn more.

bull-crabThese gigantic crustaceans emerge from deep, muddy burrows with the warm spring rains in May. The burrows are usually dug in compacted silt around salinas and seasonally flooded mangrove ponds or open salt marshes. Land crabs battle – by pushing and shoving – for the best real estate, and low areas with plenty of food and deep muddy silt can have up to 7,500 burrows per acre. Burrows can be six feet deep, and they are always dug down to the water table. At the bottom of each burrow is a chamber that lies flooded with about half a gallon of water. The water can be fresh, brackish or salty (sometimes more so than sea water). Land crabs, like all crabs, have gills. Unlike aquatic crabs that have a constant flow of water over their gills, a land crab has to carry its water supplies with it, inside its body. The water only lasts about 48 hours before it evaporates with the crab’s breathing action, and so it must be replenished at least every other day. This is why the crab digs a burrow down to the water table – to create a private reservoir of breathing water; a personal respiratory swimming pool hidden safely underground.

Mostly, Great Blue land crabs prefer to live alone, though they will sometimes escape from predators by retreating into burrows that are not their own. Only mature crabs have the stamina to dig down to the water table, so young crabs, not yet of breeding age, will often room with adult crabs. The adult crabs tolerate these boarders until they are mature.

Adult and immature land crabs emerge from their burrows in late afternoon when shadows are long and the worst of the day’s heat has passed. Their favourite foraging times are dusk and dawn, but they will also spend all night out when the moon is bright, and they sometimes venture out on overcast and rainy days. Land crabs forage for food indiscriminately, though they do have their favourites. They are mostly vegetarian – favoured foods include the leaves of red and white mangroves, buttonwood and purslane. They will also eat other plants, and will occasionally catch insects and other small animals, including lizards and snakes. Dead animals are also welcome feasts, and they are even known to be cannibalistic. As the crabs forage for these salt marsh delicacies, they begin putting on weight and preparing for courtship.

Male crabs, locally called “bull crabs,” court females soon after they emerge in May. Male Great Blue land crabs are larger than females, with longer legs, a brighter blue hue and one hugely enlarged “biter” or claw. This enlarged claw’s two “fingers” meet only at the tips, and is used to wave at other male rivals and occasionally in battles to turn other males over. Despite its terrifying appearance, the large claw is less dangerous to people than the other claw, which is smaller, has a jagged internal surface and meets along its lengths like a pair of cutters. Females, which are usually lighter in colour with rounder bodies, have two such shear-like claws, making “she-crabs” dangerous pinching machines.

Fertilisation is internal, but when the female lays eggs, she carries them on the outside of her body, clutched tight to her belly with a broad, triangular tail. Female Great Blue land crabs lay large numbers of eggs in relation to their body size, and can produce egg masses numbering from 300,000 to 700,000 eggs. The eggs are brown, gummy, and each about the size of a poppy seed. Female crabs carrying eggs are locally said to be “with sponge.” Within two days of laying eggs, the she-crab must deposit them into the sea, which can mean an adventurous journey for a crab that may live as far inland as five miles.

Using the setting sun’s light at the horizon, sensing ground vibrations, remembering landmarks and feeling for wind direction, she-crabs with eggs make their way toward the sea at night, within a few days of the full moon.  At the water’s edge, they “wash sponge” – that is, release their eggs into the sea water. Female crabs then return to their inland homes and will breed several more times in a season if the food supplies in their home territory allow.

What becomes of the eggs after the she-crab “washes sponge” was only recently understood. The eggs hatch into free-swimming larvae that look very little like the crabs they will someday be. They go first through a phase of drifting called a zoea, then as they grow and moult, feeding on other plankton, become an actively swimming megalops. After 30 to 40 days, the megalops has grown and moulted enough to go through a final aquatic moult, and emerge from the sea as a tiny land crab.

The land upon which the tiny crab emerges may not be its homeland – the planktonic larvae can drift miles on ocean currents and end up on shores far from where they are laid.  However, on islands with still lagoons and abundant tidal saltwater creeks intruding into the land (such as the southern shores of the Caicos Islands), crab larvae may well end up on the same islands from which their parents came.

Young Great Blue land crabs start out life with a brown body and orange legs, and it takes them four years to moult enough to reach adult size. These crabs are slow growing, and they may moult as many as 60 times before they can reach their maximum size. Moulting is carried out during inactive seasons, when the weather is dry.  After actively foraging in the warm, wet Turks & Caicos summers, the Great Blue land crabs seek out their burrows as the dryer winter months approach. By October, most crabs have not only retired to their burrows, but have even plugged the entrances with mud to keep out enemies. Underground in their deep, wet haunts, they moult. Moulting is a six to ten day process by which the crabs shed their outer shell so that they can put on a rapid burst of growth before the new shell hardens. After the moult, the crabs may remain in their burrows, living off of stored fats in their bodies, until the next year’s warm spring rains entice them to emerge and forage again.

When Great Blue land crabs do emerge and forage, people, and some birds, are waiting for them. In Kew, North Caicos, “crab season” is heralded by the sounds of young boys hard at work hammering together scrap plywood and pallets to build crab pens, and the sight of them walking the roadsides at night with flashlights and rice sacks. Often, entire families join in the hunt for crabs. A single crab can sell for three to five dollars locally on Middle and North Caicos, but can bring as much as seven dollars when sent air freight to Grand Turk.

Most people prefer to leave town to hunt crab – a crab found in a settlement may be the same one that was seen crawling out of a neighbour’s latrine the night before.  A visit to the airports of Middle and North Caicos in the warm months can often yield the sight of a cardboard box riddled with holes from which the odd leg or claw pokes, rattling with the sound of tightly packed crabs scratching around inside, taped securely shut with handwritten lettering indicating the destination as Grand Turk or Provo.

Having accompanied friends, both old and young, on crab hunts I learned that there are a number of methods people use to avoid the horrible “biters.” A machete can be used to press down on the crab’s back before lifting it by the hind pair of legs or the back of the shell. Alternatively, a solidly shoed foot can clamp the crab down while each claw is firmly grasped. Hooks and nets can also be used, and a dog I once had even learned to chase crabs out from the bush into the open so his former owner could catch them. (This dog was a potcake, but due to his crab hunting prowess, I considered the possibility of registering a new breed – the Caicos crab-hound!)

But one doesn’t necessarily need a light and a machete and a bag to hunt crabs – a pickup truck will replace all other equipment. Drive down any North Caicos road on a rainy summer night and no doubt you will encounter a slow-moving pickup truck. It’s not careful driving, it’s 21st-century crab hunting. Simply sight crabs in the headlights, blind them with the high beams, jump out and sling the crab into the bed of the truck. This method isn’t without its own risks as Great Blue land crabs have been known to puncture tyres!

crab-bucketOnce the crabs are bagged up (or in the bed of the pickup truck), they are transferred into the crab pen – often a clapboard hutch rife with the sound of scratchy sideways scurries of a hundred pokey feet. Feed the crabs up with old rice, vegetable peelings . . . pretty much anything (the preferred food for fattening in the Bahamas is soaked corn), give them a pan of water and you have a pantry of fresh crabs available indefinitely. Though one will occasionally find a she-crab carrying sponge in a crab pen, most gravid females are left alone. Crab hunters understand that those thousands of eggs need to get to the sea in order to replenish populations for future generations. Nonetheless, some old timers enjoy the taste of crab eggs roasted in fire!

Most crabs will end up as crab ‘n’ rice, though there are a multitude of dishes made from crab. The crab’s fat reserves are used to flavour rice dishes and the meat in the claws and upper leg segments can be steamed and picked out to make crab salad or crab cakes. Only the shell and guts are discarded. The meat from the tips of the legs is excellent fishing bait. Crabs happened upon out of season will occasionally be eaten, but they are not popular because they lack the fat reserves of in-season crab.

It is not only humans who pursue these delicacies. The crab’s number one enemy is the Yellow Crowned Night Heron, locally called the gaulin. Gaulins strike the back shell of a crab with a stout, sharp beak, puncturing the crab’s nerve centre and stunning it. They then eat the legs, smash the claws and shell against rocks and devour the innards. Night herons can’t digest crab shells, and spit them back up in a mosaic-like pellet. Finding a crab shell with a half-inch hole through it is proof that a gaulin has been eating well in the area. During the winter, gaulins have to hunt ghost crabs on the beach and the young black and orange colored Great Blue land crabs, locally called “kittykee,” as they emerge from the sea. But during crab season, gaulins eat as well as the people do.

Crab season is defined, in the Turks & Caicos Islands, by the crabs. There is currently no legal open or closed season for crab hunting, and there is no bag limit. In Florida, crab season is open only when they are not reproducing – from November 1 until June 30 the following year – and there is a strict bag limit of 20 crabs per person per day. In some areas of the Bahamas, crab replenishment areas have been created where hunting is prohibited, to ensure abundant future stocks. At this time, Great Blue land crabs remain plentiful in the Turks & Caicos Islands.

Great Blue land crabs aren’t the only land crab hunted in the Islands. The Black land crab, known in the Antilles as the Mountain crab Gecarcinas ruricola is said to have a sweeter taste than the blue land crab, though it has less meat and fat and is therefore more work to prepare. The smaller Rainbow crabs Gecarcinas lateralis zoom swiftly along the sand dunes, though are too small to be worth eating. Likewise the well known Soldier or Hermit crabs Coenobita clypeatus make better pets than they do dinner.

The Great Blue land crabs, though, are most numerous . . . and most coveted. Recently, I knew I had a Great Blue in my garden when I saw the damage to my hot pepper plants and the telltale scratchety feet tracks in the soil. I knew it was hiding under a piece of plywood. So I picked up the plywood. Ugh! Not one horrible windup mechanical vindictive spider robot. Three! I dropped the wood; I’d need reinforcements. I grabbed my garden trowel and donned my flip-flops because one can’t go into battle unprotected. I lifted the plywood. I stomped and swung my garden trowel and swore and hissed. The crabs did the same. Except they all did it in different directions while attempting to remove my extremities. This called for more backup, so I beefed up my weaponry with a big plastic plant pot. There was screaming, and falling, and kicking, and stomping, and thwarted crab claws and garden trowels. One got away. But I successfully cornered the other two arthropodic horrors in the plant pot and dumped them quickly into a bucket. I looked down at them, out of breath from my partially successful attack, and wiser to their lifecycle and role in the ecology of the Islands – and slightly happy that one got away to continue that cycle. I then whisked the other two away immediately to my neighbour, who had been looking for some. She’s having company tonight, for dinner. And the crabs aren’t the company.

Bibliography

Arthur, Jannay. Turks & Caicos National Trust, May 2008.

Hill, K. “Cardisoma Guanhumi.” Fort Pierce Smithsonian Marine Station, 25 July 2001.

http://www.sms.si.edu.IRLspec/Cardis_guanhu.htm

Hostetler, Mark E. Mazzotti, Frank J. & Taylor, Amy K. “Blue Land Crab.” University of Florida Institute of Food and Agricultural Sciences, January 1999.

http://edis.efas.ufl.edu/UW013

Lockhart, Kathy. Department of Environment and Coastal Resources, May 2008.



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Marta Morton, owner of Harbour Club Villas, shot this photo on the magical island of Salt Cay. The foreground is filled with the endemic National Flower Turks & Caicos Heather in full bloom. St. John's Anglican Church, built in the early 1800s, is in the background. To see more of her work, visit www.myturksandcaicosblog.com

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