Fighting crabs

 A few years ago, on a hot summer afternoon, I was watching the tide roll in over a rocky breakwater. As the water rose between the rocks, crabs started to come out from their hiding places. More crabs and more, where a few minutes ago there had been no sign of life, just the hot, bare rocks.

The water rose until it reached a dried kelp stipe, cast up to bake on the rocks. And this surprised me: immediately the crabs attacked it; all the crabs, jostling and scrambling over each other to get at this dried kelp. More came out from hiding, dozens and dozens more, all of them grabbing at the stipe, fighting for a spot, pushing each other out of the way, tearing off bits and eating them. As the tide covered more of the length of kelp, so did the crabs until there was no kelp to be seen, just this dancing mass of crabs.

I should have thought of this sooner. My hermit crabs like kelp, too, and I would bring them fresh kelp from the shore. But cut kelp quickly turns slimy; I could feed them only a small piece and throw away any extra. And then, last fall I remembered the happy crabs.

So now I slice a long stipe into thin circles and dry it. And every couple of days I give the hermits and crabs a couple of dried slices. The first batch lasted them all winter; now they're starting on a stipe I dried a couple of weeks ago. 

Hairy hermit and his kelp treat.

One of the tiniest hairy hermits, with his scrap of kelp.

And a watchful crab, ready to fight for her meal, if necessary.

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Hace unos años, en un verano caluroso, estaba en un rompeolas mirando mientras subía la marea. Cuando el agua empezó a cubrir las rocas, aparecieron los cangrejos que hasta entonces habían estado bien escondidos, fuera del alcance de los rayos del sol. Más cangrejos, muchos cangrejos, donde hacía poco no se veían señales de vida, solamente esas piedras resecas.

El agua subió hasta que alcanzó un tramo del estipe de quelpo ya bien seco, tostado por el sol allí expuesto sobre las rocas. Y esto me sorprendió; en cuanto el agua tocó el quelpo, los cangrejos lo atacaron; todos los cangrejos, con gran entusiasmo empujándose, trepándose uno encima del vecino para llegar a este pedazo de quelpo seco. Salieron más de sus escondites, docenas más, todos tratando de agarrar el quelpo, peleando con los que se pusieron en su camino, defendiendo su sitio con ánimo mientras arrancaban pedazos para comer. Mientras la marea cubría más del quelpo, también lo hicieron los cangrejos, hasta que no se veía nada del alga, solamente esa masa pululante de cangrejos.

No sé porque no pensé en esto antes. A mis cangrejos ermitaños también les gusta el quelpo, y yo les traía pedazos desde la playa. Pero el quelpo cortado pronto se hace baboso, y solamente les podría dar un pedacito y tirar todo lo demás. Hasta que el otoño pasado, me acordé de esos cangrejos felices.

Y ahora me traigo todo un estipe largo, lo corto en rebanadas delgadas, y lo pongo a secar. Y cada dos o tres dias les doy una o dos rueditas de quelpo a mis criaturas. El primer estipe nos duró todo el invierno; ahora empiezan con el segundo. Y muy felices están.

Fotos: 

1. Un ermitaño "peludo" Pagurus hirsutiusculus, con su pedazo de quelpo.
2. Uno de los más pequeñtos, también comiendo quelpo.
3. Y un cangrejo hembra, algo preocupada por pensar que yo le puedo quitar su hallazgo. Lo defenderá con esas pinzas, si llega el caso.

While I waited

 A browsing deer, tiptoeing delicately through the thimbleberry patch, hears me coming and stiffens into immobility, a few inches taller already; neck, ears, legs all suddenly stretched. If she thinks I may be a danger, she leaves, bouncing straight-legged through the undergrowth.

A bear doesn't bounce. He shuffles. Like a fat man in baggy trousers, not in any hurry, unconcerned, he plods down a trail. His apparent slowness is deceptive; he's gone behind the trees in a moment.

Range cattle. Heavy. Slow. They stand watching, pondering; should we move out of the way? When they make up their minds, its as if the weight were almost too much for their legs.

Every live thing has its own way of moving. Even when we capture only a glimpse, under the trees, in the undergrowth, half behind the rocks, we can recognize them by their gait.

The same goes for the tiny beasties, the flying, crawling, sliding critters. In a tide pool full of seaweeds, a flash of twisty,  splashing movement, gone in an instant, alerts us to the presence of a gunnel; a quick, sharp, straight-line dash into the dark is probably a sculpin. Crabs scuttle sideways, feet first and last. Flatworms ooze like a smear of oil. Anemones caught off guard shrink inwards.

In the aquarium, the crabs dig crab caves. Sliding to the right, dragging sand; slipping quickly back to the left, slightly downhill. Then back dragging sand again. Snails slide along so slowly, then suddenly haul themselves forward with a jerk as they bring their body up to their foot. Hermit crabs, even at rest, are never still; they wave long antennae and bright flag-like antennules constantly. Amphipods are in a continual flutter.

In the wet sand left after I washed off a new batch of eelgrass, a couple of the sand grains were moving. This way, rolling; that way, falling back. Looked like crabs to me, but so, so tiny! The hand lens confirmed it. I gently tipped the sand, with sand-grain crabs into the tank.

I saw them again when I next cleaned the tank, hiding in a corner away from all the activity. Still barely visible. Next, one turned up at the front of the tank, under a rock, excavating his miniature cave. Every time I passed, he was there, busy moving sand one grain at a time.

I found some time and got out the camera with the macro lens and the auxiliary flash, cleaned the glass and sat down to wait for him. And waited. He'd finished making his den, and crab-like, abandoned it to start digging somewhere else, out of sight.

It's all good. I took photos, while I waited, of other tinies.

Young hairy hermit, on section of kelp stipe.

The crab's rock. It was covered in barnacles, but the crabs (larger ones) have eaten most of them and now orange-striped green anemones have moved into the empty shells.

The same stone. With one of the remaining barnacles out fishing.

Eelgrass isopods. Usually they're green; this one, and her babies (look among the red algae beside her) are a dull grey.

The kelp crab again. He's lost his sea lettuce cap and added a bit of rockweed.

On top of the sand where I was looking for the crab, an amphipod.

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Un venado se mueve tranquilamente entre las hierbas, comiendo hojas de frutillas. Me acerco y se endereza, estirando las orejas y el cuello; parece que ha crecido en ese momento. Ahi se queda, como congelado, una estatua viva. Se le ocurre que yo pueda ser peligrosa y se aleja, saltando con las patas tiesas hasta desaparecer entre la maleza.

El oso no salta. Anda sin prisas, sin urgencia. Se ve como un viejo hombre gordo en pantalones grandes y flojos. Como si no te viera, como que no le preocupes, va holgazaneando hasta esconderse tras unas rocas.

Las vacas que andan libres por las montes. Son pesadas. Lentas. Se quedan paradas, mirándote, pensando; —¿Vale la pena salir del camino? — Se deciden después de un rato, pero es como si su peso fuera demasiado para moverse a prisa.

Cada cosa viva tiene su propio movimiento. Aún cuando solamente captamos un vistazo, una curva, unas orejas, unas ancas peludas, ya debajo de los árboles, entre la maleza, tras las rocas; aun así las podemos reconocer por la manera en que se mueven.

Lo mismo pasa con los animalitos pequeñitos, los que vuelan, se arrastran, corren o nadan en las grietas que pasamos sin mirar. En un charco dejado por la marea, lleno de algas marinas, un movimiento rápido, ondulante, y casi de inmediato detenido nos indica la presencia de un pescadito espinoso de marea. Algo que nada rápidamente, como una flecha dirigida al punto más oscuro probablemente sea una esculpina. Los cangrejos corren hacia un lado, con las patas por adelante y atrás.  Los platelmintos (gusanos planos) se escurren como un borrón de aceite. Las anémonas cuando notan nuestra presencia, se encogen y se encierran.

En mi acuario, los cangrejos se hacen cuevas. Se arriman hacia el derecho, jalando y empujando arena consigo, luego regresan sin carga a la oscuridad para recoger más. Los caracoles marinos se deslizan lentamente, y de repente dan un saltito para adelante, trayendo su concha al nivel de la pata. Los cangrejos ermitaños, aun cuando están parados, nunca se quedan quietos. Agitan las largas antenas constantemente, sacuden las banderitas (atenulas) arriba de la cabeza. Los anfípodos vibran continuamente.

Entre la arena mojada que quedó después de lavar un manojo de hierba Zostera, algunos de los granos de arena se movían por si solos. Rodaban para allá, caían para acá. Movimientos de cangrejo, pero ¡tan, tan pequeño! Con una lupa lo confirmé; era un par de cangrejititos. Con cuidado, los vertí en el tanque.

Los vi de nuevo la próxima vez que limpié el tanque, escondidos en una esquina lejos de toda la actividad. Todavía apenas visibles. Luego, uno se presentó en la pared de enfrente del tanque, debajo de una piedra, excavando su cueva miniatura. Cada vez que yo pasaba, allí estaba, ocupado en mover la arena, un grano a la vez.

Cuando tuve tiempo, saqué la cámara con la lente para fotos macro, y el “flash” auxiliar. Limpié el vidrio y me senté a esperar a que saliera mi cangrejito. Esperé. Esperé. No apareció. Aparentemente había terminado de construir su cueva, y a la manera de los cangrejos, de inmediato la abandonó para empezar a hacerse otra, en otra parte.

Total. Todo está bien. No perdí el tiempo. Mientras esperaba, tomé fotos de otras criaturas miniaturas.

Las fotos:

• Un ermitaño pequeño en un pedazo de estipa de kelp. 
• La piedra donde el cangrejito había hecho su cueva. La parte superior había estado cubierta de bálanos, pero los cangrejos más grandes los han estado comiendo. Ahora un grupo de anémonas ha ocupado las conchas vacías.
• Otra foto, con un bálano pescando.
• Una isopoda con su cría. Mira entre las algas rojas al su lado.
• El cangrejo kelp otra vez. Ha perdido su gorro de alga verde, y ahora lleva un pedazo de alga amarilla.
• Y en la superficie de la arena, donde buscaba el cangrejito, un anfípodo.

Lady B., Earth Mover

One of the things crabs do best (and most) is dig. Dig and dig and dig, making holes, burrowing under rocks, undermining oysters; all day and all night. And when they've finished a burrow to their satisfaction, they up stakes and move on, to dig somewhere else.

I discovered Lady Bird* digging right up against the aquarium wall, and videotaped her.



*Named for her "feathers".

Bullies, devourers, thieves, and pacifists.

Continuing with the July assortment, these are animals in my aquarium and on local shores.

The bullies first.

Crabby. All blue-eyed innocence, except for those menacing pincers.

Crabs are fun to watch; always busy, always on the move. I had three in the aquarium, and they were thriving, molting and growing, scrambling everywhere, re-arranging rocks three times their size, rolling snails and tearing the sea lettuce. All well and good, until they grew big and fast enough to attack their tank mates.

There were three big rockweed isopods, inoffensive seaweed grazers, bigger than the crabs. They'd come in with seaweed long ago. The crabs grabbed and ate two; I caught ol' blue-eyes in the act.

They ate one of the big hermits. And my old red shrimp. There was no need for that: I've always fed them well.

So I fished them out of the tank and hauled them down to the beach, where they strutted into the waves, waving pincers, ready for action. They didn't know about fish and gulls yet.

The remaining residents of my tank breathed a sigh of relief. Or would have, if they were breathers.

Signal crayfish, Pacifasticus leniusculus. Identified by the white markings at the wrists.

We found this crayfish, dead, floating in the shallows of the Campbell River mouth. Another aggressive predator: they will eat anything, from rotting vegetation to live fish and their own relatives. My son had one that got in among his goldfish, ate them all, and grew very big.

They're a freshwater crustacean, but tolerate brackish water, freshwater mingled with tidal surges.

A bright orange starfish. (Blood star, maybe?) Stories beach. A notorious predator.

The Monterey sea lemon. Trundles around slowly, eating sponges and other sessile animals (fixed in place, like barnacles.) On Stories beach, at the south end of Campbell River.

Pale pink and green anemone in my tank. It arrived as a mere speck on a shell, and now has grown to half an inch across. I rarely feed these; they thrive on copepods and other plankton. Including, possibly, all those baby hermits.

Orange-striped green anemone, Duodumene lineata.

This one was on Stories beach, but a few tinier ones came home with me on a stone full of barnacles for my Leafy Hornmouth snails. I counted seven tonight after I cleaned the tank.

The tiniest of the fishermen; a two-tentacled worm (a Spionid) in a hole in an old shell. They catch detritus, which slides down the tentacles into the mouth.

Another, with leftover sand grains around the mouth. The worm cleans off the edibles, and spits out the sand.

One of my hermits, a Hairy.

These guys eat leftovers, dead critters, seaweed, hydroids and diatoms when they can. Totally inoffensive. Except when they see one of their friends with something good; they're not averse to rolling him over and stealing his food. Especially if he is smaller than they are.

It's a dog eat dog world in there.

A bully, a devourer of barnacles (Leafy Hornmouth snail), and the pacifist limpet, who putters mildly about cleaning algae off the rocks and the glass.

Weight-lifting mama

They say ants are the best weight lifters, lifting 20 to 50 pounds their own weight. I think maybe crabs have them beat. Small crabs move stones or shells much larger than themselves, often laden down with seaweeds and other critters on top.

I've been watching the tiny black-clawed crabs in my tank. The female is still only about a centimetre (1/2 inch) across, and weighs about 2 grams, according to my food scale*. She has chosen the base of a large stone as her preferred hiding place, kicking out the larger male who lived there earlier. Yesterday, the stone was tipped almost onto its side. This morning, it was straightened up again, but turned at a right angle from its previous position.

I took the stone out and weighed it. A little over 250 grams, more than half a pound, That's over 100 times the weight of the crab that's shifting it around.

Two legs to hold the rock, four to lift it, and two pincers to wave at intruders.

(*I weighed her in a plastic cup, with a bit of water for comfort, and then the cup and water alone. The crab made barely any difference.)

All bark and no bite

The tiny black-clawed crabs that arrived in a holdfast six weeks ago are growing up. The largest, a male, was 5 mm. across the carapace; now he's three times that. He has chosen a hiding spot behind a big rock, but up against the glass - it feels solid, I guess, even if it's transparent - and I've been trying to get his photo. He usually responds by threatening me with dire harm.

"Armed and dangerous, I am!"

His multi-coloured shell and legs are good camouflage in the mess of shell pieces and stones he collects around himself. The back legs are usually raised, holding the rock behind him.

His usual pose; always with those dark pincers raised and ready for action.

When I give the tank a thorough cleaning, I remove the animals to a bowl first. I have to chase my speedy green shore crabs around and around for quite a while; even caught, they struggle to get free. These little black-clawed crabs, once I've removed their sheltering rocks, walk away casually; no worries. When I pick them up, they sit quietly in my hand, not even bothering to threaten me. But once in the bowl, they quickly scuttle under the closest shelter.

The second largest is a female, and very much in berry; her whole underside is a mass of dark eggs. She hides in a crack between two stones, and rarely shows more of herself than the warning pincers. Hers are mostly a dark brown colour.

And I haven't been able to lure her out into the open for a photo op. I haven't wanted to stress her by taking her photo on my hand, so I'll keep watching the door to her hideout, camera in hand.

Deportation proceedings: Part 2 The accusation

There's nothing cuter than a baby crab.

Case in point; "Smiley". 2009 photo.

Trouble is, shore crabs do very well for themselves in an aquarium; steady temperatures, clean water, ample diet, and no predators, to boot! So they grow up large and strong.

And the bigger a crab gets, the more disruptive he becomes. He digs himself a deep burrow, throwing aside carefully-placed landscaping and piling leftovers on top of his neighbours' land. He then goes out to steal food from whoever has any, and retreats to his hole to eat it all in peace. No sharing! When his hole gets untidy, as it does - he's a messy eater - he abandons it and digs himself a new shelter. Again, he tosses his construction trash next door.

In between, he goes a-hunting. Freshly-molted young hermit is tasty; so is a snail that he can crack between his pincers. He can snatch a speeding amphipod out of the water without a miss. And a nice mouthful of green sea lettuce makes a good garnish. Leftovers are tossed into the current.

But even the non-edible, glued-in-place residents come in for their share of harassment. Enter the burrowing anemone.

"Val", from Campbell River. Nicely healed, growing a sturdy, button-studded column.

Hermit crabs crawl all over the anemones, picking up bits of debris, grooming the tentacles. Sometimes the anemone shuts down for a bit; more often it doesn't. They're friends. Big Patch, the crab, tried to imitate them, but was not welcomed, probably with good reason. I watched on several occasions as the crab approached. When he came within reach of a tentacle, he leaped backwards, as if shocked. He tried over and over, always with the same result. The anemone's stinging cells are good protection.

Revenge is sweet, says Patch.

He dug a hole right next door, and buried the anemone with broken shells and gravel. Val shut down; can't feed under all that heavy construction debris. I raked through the stuff with my fingers, removed the gravel, left clean sand around the base of Val's column.

Patch dug another, deeper hole. Val shut down. I cleaned up. Patch pushed a load of sand halfway across the aquarium and piled it on top. I cleaned up.

Burrowing anemone, White Rock beach.

(On the beaches, most of these anemones cling to rocks, sheltered from tidal sand pile-ups. I accidentally dug up the one above that I found in sand instead, by trying to measure its column depth with a finger. It had nothing to hold it, and rolled out of the sand. A wave caught it and hauled it away, probably food for whatever fish got to it first.

The anemones on the beach in Campbell River, where Val originated, usually anchor themselves in sandstone pits, sheltered by seaweeds. There is very little loose sand for the crabs to move about.)

Cluster of anemones in sandstone, Storries Beach, Campbell River.

Val has anchored hirself to the glass bottom of the aquarium, for safety, but that means only a certain depth of stuff will be tolerated around the column.  Patch kept burying hir.

Eventually, I moved Patch's favourite clam and oyster shells to the far end, re-arranged all the landscaping, plants, rocks and all, so as to leave nothing nearby to be piled on top of Val. Overnight, Patch hauled it all back, and re-buried his enemy.

Patch, showing off his Alpha male, XL pincers. Val in the background, shut down. What's the sense of fighting back?

So: it's time. Patch is too big for his britches, too big for a tank he must share. He's been exiled to a quarantine tank, with a couple of other growing crabs. Next trip to the beach, they're going along. They'll do fine there; they're large and healthy, if a bit spoiled.

Val is sitting in an empty plane, in lonely splendour, waving tentacles happily in the current.

Deportation proceedings, part1

On the beach, they live together amicably, the animals and plants that end up in my aquarium. All but one have come from the upper intertidal shores of Boundary Bay, where shore crabs and hermits (hairy, grainy-hand, and greenmark), worms, clams, mud snails and periwinkles, amphipods and burrowing Nassa snails, and the occasional anemone abound. Val, my one import, comes from Campbell River; on hir beach, we found the same crabs and hermits, snails and worms. So they should do well together in the tank, right?

Not so fast! On the beach, they do tend to separate into zones; there's a wormy patch, with snails on the surface; there's a clean sand patch, with clams underneath and crabs on the surface; there's a snail and hermit area, with worms underground. On our Campbell River beach, there were patches of mostly anemones where the tide pools were full of hermits and snails.

The combinations may be due to water current variations, to the size of the sand grains, to the number of rocks, or the varying salinities and temperatures of any intertidal zone. But personalites may enter into the equation, too.

Hermit crabs get along with each other nicely, even across species lines. They're fine with anemones; they clean up the shells of snails and clams without disturbing their owners. They eat barnacles or worms, but only when they find them already broken. They have no fight with "true" crabs.

Mud snails, periwinkles, and the little Nassas go about their business eating algae and detritus, ignoring anything else. They stay away from anemones, though; the anemones do sting when they're pestered.

But the crabs! A different story altogether. A crab is the top dog on the totem pole, in his own eyes. He'll get along with anything else, as long as it keeps out of his way, gives up its choice tidbits of food, doesn't invade his current hole. Or doesn't look too tasty, like, for example, a newly-molted hermit or a snail small enough to crack like a nut.

Unfortunate hermit, looking for a shell, with a crab waiting below him. Crab dinner.

And a mature male shore crab is the top-doggiest top dog of them all.

Patch, recently molted, grown to his full size, ready for action.

Next: the case against Patch.

Eight-legged hobbit?

Hermit crabs live in borrowed snail shells. "True" crabs hide themselves under rocks, or bury themselves up to the eyestalks in the sand. But one of my little crabs has taken a hint from the hermits.

I provided an assortment of shells for the hermits; whatever I could find or had collected from other sources. Some are from local beaches, some from Mexico and Central America, a few from unknown shores, shells I picked up in garage sale lots.  But hermits have their likes and dislikes; some will accept even non-shell outfits, made of glass, broken bottle caps, or even Lego (look!) but many have very specific tastes. Mine, hermits from Boundary Bay, will only wear discarded shells from local species of marine snails: whelk, mud snails, or periwinkles. Everything else is invisible to them, so far.

One of the smaller shore crabs discovered a broken shell ignored by the hermits, and moved in.

Hobbit house* shell, from down south, is about 1 1/2 inches across.

The shell makes a great shelter; front and back doors, complete privacy, no maintenance. The crab stays inside most of the time, even when I pick up the shell as I clean the aquarium, or when larger crabs push it around. He comes out when I provide crab treats, only to grab his share and retreat to eat it in his own space.

I was surprised, a couple of days ago, to see him out of the shell, digging busily deep in the sand a couple of inches away. I watched. After a minute, he surfaced carrying a large white stone, which he carried over to his home shell, and deposited in the doorway. There were already several others there, in both openings.

Front door, back door, with privacy screens. He's well hidden inside.

The stones fell out when I tidied the aquarium yesterday, but he's since added a new sandy floor inside and three fresh stones at the doors.

*It had a perfectly round door like a porthole, painted green, with a shiny yellow brass knob in the exact middle. The door opened on to a tube-shaped hall like a tunnel: a very comfortable tunnel without smoke, with panelled walls, and floors tiled and carpeted, provided with polished chairs, and lots and lots of pegs for hats and coats ... J.R.R. Tolkien, The Hobbit