Crabs

(An extract from ‘A Naturalist on the Prowl’ by E.H. Aitken)

Prowling on the seashore one evening, I espied another prowler, and he espied me, and avoided me as the burglar avoids the policeman. He did not run away, but just deflected his course a little, took advantage of a dip in the sandy beach, got behind a growth of screw pines and was not there. It was getting too dark to see clearly, but by these tactics I knew that he was a jackal. He had come down in the hope of catching a few crabs for his supper. Scarcely had he got himself away when, with a shrill squeak and a scrambling rush, a fat musk rat escaped from my foot into a heap of stones. What was it doing there? Hunting for crabs. Now there is something very revolting in the thought that crabs are liable to be killed and eaten by foul jackals and disgusting musk rats. The crabs are a peculiarly interesting people, like the ancient inhabitants of Mexico, unique and not to be ranked with the other tribes of the earth.

Professor Owen holds that the hand of man suffices to separate him from all other animals almost as widely as any two of them differ from each other. “The consequences,” he says, “of the liberation of one pair of limbs from all service in station and progression are greater, and involve a superior number and quality of powers, than those resulting from the change of an ungulate into an unguiculate condition of limb.” Think me not a mocker if I suggest that the crab shares this endowment with man, and perhaps that is the reason why he seems to stand apart from all other creatures that are clothed with shells. By pedigree the crab, I admit, is but a prawn which has curled its tail under its stomach and taken to walking; but no one who has lived much among crabs and associated with them, so to speak, can lump them with prawns and other shell-fish good for curry. A crab is not like a lower animal. He does not seem to work by instinct. All his avocations are carried on as if he had fixed principles, and his whole behaviour is so deliberate and decorous that you feel almost sure, if you could get a proper introduction to him, he would shake hands with you.

At times I have thought I detected a broad grin on the face of an old crab, but this may be fancy. I incline to the idea, however, that he has a sense of humour. He is courageous too-not foolhardy, but wisely valiant, and marvellously industrious. Watch him as he repairs his house flooded by the tide. Cautiously he appears at the door with a great ball of sand in his arms, and erecting his eyes to see if any enemy is near, advances a few paces, lays his burden down and returns to dig. Again he appears and puts a second ball besides the first, and so on till there is a long even row of them. A second row is then laid alongside the first, then a third, and a fourth; then a passage is left, after which a few rows more are laid down. So rapidly is the work done that the tide has scarcely retired when the whole beach is chequered with flowerlike patterns radiating from a thousand holes. These are the work of infant crabs mostly, for as they grow older they venture to retire further from low water mark, where the sand is dry and will not hold together in balls. Then they bring it up in armfuls and toss it to a distance. But, old or young, their houses are swamped and obliterated twice in every twenty-four hours, and twice dug out again; from which you may judge what a life of labour the sand crab lives.

The sand crabs reach almost upto the Screw pine (Pandanus) zone.

The sand crab...

...and his labour.

Plover patrol (foreground)! Watch out, little sand crabs!

He is, I think, the noblest of his race. Living on the open champaign of the white sea-shore, he learns to trust for safety to the keenness of his sight and the fleetness of his limbs. Each eye is a miniature watch-tower, or observatory, and his legs span seven times the length of his body. When he runs he seems to be on wheels: you can fancy you hear them whirr. But, keen as is his sight and amazing as is his speed, he more than needs it all; for, alas! he is very tasty and all the world knows it. In his early days the sandpipers and shore birds, nay, the very crows and preh pudor! my turkey patrol the water’s edge, and he scarcely dares to show his face by daylight. Then, as he grows beyond the fear of petty enemies, he comes within the ken of greater ones. The kite, sailing high overhead, swoops like a thunderbolt and carries him off. The great kingfisher, concealed in an overhanging bough, watches its opportunity, and when he has wandered far from his hole, darts upon him and scoops him up in its long beak. The kestrel hawks him, dogs hunt him in sheer wantonness, jackals hunt him to eat him, owls lie in wait for him, and when he takes refuge in the water, an army of sharks and rays is ready for him. And man closes the list.

“These wild eyes that watch the wave
In roarings by the coral reef’

are watching mostly for crabs. He is drawn from his hole with hooks, dug out with shovels, caught in traps, netted with nets, and even in the darkness of night distracted with the sudden glare of flambeaux and knocked over with sticks.

Man - arch-enemy and predator no 1. The crabs in the basket are Three-spotted Crabs (Portunus sanguinolentus), a swimming crab. The crabs in the basket were caught at sea by local fishermen using nets and were at Harne beach waiting to be sold. (Identification - 'Marine Life in India' by BF Chapgar.)

Many are the ways in which the race of crabs have sought to shun their thousand foes, some by watchfulness and wisdom, or cunning and skill, some along paths of degeneracy and shame. In the aeons long gone by, it seems, there lived a craven crab who condescended to seek safety by thrusting his hinder end into an empty shell, and to-day his descendants are as the sand on the sea-shore for multitude, dragging their cumbrous houses about with them and thrusting out their distorted arms to pick up food, and shrinking in again at the least sign of danger. Safety they have bought with degradation, but there are moments of supreme peril even in the base life that they lead; for the crab grows and the shell does not, and it is an inexorable law of nature that, when you change your coat, you must put off the old before you put on the new. The most ludicrous sight I ever saw was two hermit crabs competing for an empty shell. Neither of them could by any means take possession without exposing his naked and deformed posteriors to the mercy of the other, and this he dared not do; so they manoeuvred and circled round that shell and made grimaces at each other till I laughed like the blue jays in Jim Baker’s yarn.

A hermit crab (Superfamily Paguroidea)

The hermit crab drawn out in full splendour!

Others of the race have tried to win security by burying themselves in the mud at the bottom of the sea and stretching out their beggar hands for food. The hands work hard, but the stomach is starved, and in some of this family the body has dwindled into a mere appendage to a great pair of claws. Of these is the giant from Japan, whose grim skeleton, eleven feet in stretch of limb, adorns the walls of the Bombay Natural History Society. Smaller specimens are common about Bombay.

The Japanese spider-crab (Macrocheira kaempferi), largest known arthropod.

Then there are crabs which make their backs a garden and grow seaweeds and even anemones, under whose umbrageous shelter they roam about the bed of the ocean in aesthetic security.

Midway between the mud crabs and the sand crabs is one whose ingenuity and adroitness rescue it from contempt. Its hind legs are transformed into an absurd pair of shovels, and the length of its eyes is simply ridiculous. If you have patience to sit perfectly motionless for a time at some spot in Back Bay where the retreating tide has left a dead level of oozy slime, you will see a hundred of these little blueish creatures moving about and collecting some form of nourishment from the mud with their quaint and crooked claws; but move’ a hand, and presto! they are gone. In an instant they have put themselves under the mud and left nothing, except perhaps the points of their long eyes, in the air.

A Fiddler Crab.... a mere appendage to a great pair of claws.

Then there is the Calling Crab, which has fostered one hand until it has grown into a veritable Roman shield, behind which the owner may shelter himself, calmly taking his food with the other. How these hold their own I cannot tell. They are not strong, nor yet swift, nor wary; but wherever the sand is soft and black, they people the shore in countless numbers. It may be that that blazing muster of gaunt, mailed hands in orange and red, ceaselessly beckoning to all the world to come, tries the courage even of a hungry crow. I am inclined to think this is the explanation of the matter, for I have often seen one of the feeblest of the mud crabs collect in dense squadrons and perform long journeys over the open shore, with nothing to protect them from wholesale slaughter unless it was the fear inspired by such an ominous mass of legs and arms.

Sally Lightfoot! The agile Red Rock Crab (Grapsus grapsus)

Where the foaming waves dash themselves against rugged rocks and moss-clad boulders, with black fissures between, and here and there a clear pool, tenanted by anemones and limpets and a quivering, darting little fish, chafing in prison till the next tide shall come and set it free, there the sand crab is replaced by the crab of the rocks, most supple-limbed of living things. How it turns the corner of a mossy rock, as slippery as that

“plug of Irish soap
Which the girl had left on the topmost stair,”

and awaits unmoved the onset of a great wave, then resumes its meal, daintily picking off morsels of fresh moss with its hands and putting them into its mouth. A life of constant watchfulness it lives and hourly peril, as many an empty shell in the pool bears witness. Its direst enemy, I believe, is the ghastly octopus, that ocean spider, lurking in crack or crevice, with deadly feelers extended, alive to their very tips and ready for the THE SWIMMING CRAB unwary. That this gelatinous goblin should be able to master the mail-clad warrior is wonderful but true. All his armour and his defiant claws avail nothing against the soft embrace of eight long arms and the kiss of a little crooked beak.

Though their proper home is the border line between land and water, the crabs have pushed their conquests over nature in all directions. Some swim in the open sea, their feet being flattened into paddles, and these are horribly armed with long and sharp spines for the correction of greedy fishes. They have been found in the Bay of Biscay, a hundred miles from land, and are common on the coasts of England, where they are said to kill large numbers of mackerel. Bombay fishermen often find them in their nets. Other crabs inhabit the forests, climbing trees. Of these we have one beautiful species, all purple and blue.

The tree climbing Coconut Robber (Birgus latro)

Others have their home in the fields, lying buried during the months of drought, and coming to life when the rain has softened the earth. They love the rain, and often have I drawn them from their holes by means of a fraudulent shower from a watering can. Slowly the poor dupe comes out to enjoy it, and when his feet show themselves at the door, you can thrust in a trowel and cut off his retreat. Then he knows he has been fooled, and backing into a corner, extends his great claws and defies the world.

Did you ever see a motherly land crab with all her children about her, leading them among the tender grass on which they feed, like a hen with her chickens, and when their little legs are weary, gathering them into her pouch and carrying them home? It is a pretty picture, and I wish I could paint in the father of the family; but the truth must be told, and I am afraid that when he meets with his offspring, he runs them down and eats them. At least I saw such a chase once. Never did crab flee as that little one fled from the chela sequentes of his dire parent. He doubled and dodged and ran again, but all in vain! He was caught and nipped in two. Then came Nemesis in the form of my dog, and the pursuer was pursued. In his flurry he lost his way, and darting into the wrong hole, all but fell into the arm~ of a bigger crab than itself. Darting out again, he was instantly crushed by a great paw.

You may ask how I know that the big crab was father of the little one. I do not know that he was; but what does it matter? He did not know he was not.

A family meal!

Image credits & licensing information :

• Note. This document is published under Gnu Free Documentation License.
• Line drawings F.C. McRae in the original print of E.H. Aitken’s ‘A naturalist on the prowl’ and are accordingly public domain.
• Photos of screw-pines, sand crabs, plover patrol, crabs in basket – self. [Licensed under Creative Commons 3.0 with Self-attribution].
• Remaining photos taken from Wikimedia Commons. Please search among category ‘Crabs’ for the source images originals and their exact license restrictions.

(a) Sally lightfoot. Marc Figueras. GFDL.
(b) Hermit crab. Hans Hillewaert. Creative Commons Sharealike 2.5.
(c) Coconut Robber. Mila Zinkova. Choice of GFDL and any of the Creative Commons licenses as listed.
(d) Hermit crab outside his shell. Public domain.
(e) Fiddler Crab. Public domain.

Note 2. After I had written this blog, I realised that I had bought a natural history book some time ago about creatures of the sea. I dug it up from my book box and began reading it. I was surprised – here was so much that I wanted to learn and and all the while the book was waiting patiently for me to fetch it from its place. I’m referring to  ‘Marine Life in India‘  written by B.F. Chapgar, the renowned Indian marine biologist and doyen of the BNHS. Published as recently as 2006, it is written in a very easy to read and understand style, with nice photographs, lots of small chapters each concerning a group of animals or aspect of sea life and lots and lots of line-diagrams. If this blog about crabs interested you, and you are an amateur naturalist in India who would like to learn more about this fascinating new world, don’t have second thoughts but go out and get your own copy! It costs Rs 350/- which is not costly for such a book by today’s standards.

Disclaimer. Please note I have no commercial considerations with Oxford University Press and I am not unfortunately personally acquainted with the author.