Invasion of the Land Crabs

You know the adage, “April showers bring… OUT THE BEASTS!”  At least, that’s how it is known on the Osa.  Last weeks’ substantial rains have brought forth multitudes of Gecarcinus quadratus, affectionately known as, the Halloween Crab, due to its orange and deep purple coloration and jack-o-lantern resemblance.

Pincers raised in the air, stumbling over the landscape when approached by person, bike or car… they summon memories of a zombie apocalypse and I have seen tourists pack their bags and leave the area as if witnessing one.  “We did NOT sign on for a wall of invading creepy spider looking thingy’s” is how one harried guest described her reason for cutting their stay short.  And, I can relate to her disdain.  Coming home last night, the headlights from my quad illuminated my garage floor literally moving with these escaping arthropods.  Inevitably, more than a few get a close up of the tire treads, and the following morning I need to collect the bodies and toss them in the compost.  More infuriating is the damage they do to whatever items are left on ground level.  Surf leashes are susceptible to nips and cuts from their pincers and a broken leash on a big day at Hogs Hole is not a pleasant affair.  Likewise, neglecting to shake out your shoes before putting them on can often result in a podiatric surprise.

Still, there is fun to be had with these crab migrations as well.  A spirited game of crab golf can entertain club swinging players, with a good drive carrying about 20 yards.  I once harvested the crustaceans that haphazardly fell into our kids outside shower/bath.  About a dozen of the prisoners went into a cardboard box with a handmade sign saying, “Homegrown Organic Matapalo Land Crabs. 500 colones each.” I brought this to Buena Esperanza, our local restaurant/bar that hosts a farmers market on Friday nights, and nearly made enough coinage to buy a beer before a local do gooder adviced the unsuspecting buyers that, no, they do not make a good bisque. 

But none of this addresses the question of, why do they migrate en masse?  Their burrows provide safety and enable them to store the fallen leaves and organic material on which they feed.  This is their ecological benefit as soil exchangers… excavating nutrient poor soils from below and replacing them with biomass from above.  Like gophers, not something you want in your manicured lawns and vegetable gardens, but surely benefitting the natural flora by deepening and enriching the soil horizon.  

Gecarcinids normaly live inland however, they have retained a marine planktonic larval phase and adults (or, at least females) must take annual migrations to the shore.  The migration is certainly related to rainfall or low barometric pressure as the first rains in April and May bring them out of their crab holes and onward to the ocean where the female deposits the fertilized eggs.  This is due to the propensity of the crabs to dehydrate in high heat. Reproduction is sexual and can only take place when the females’ calcified operculum softens. 


Now that I am more educated to these interesting organisms, I may put the driver in the bag and bring out the sand wedge for a softer return to the margins of the property.