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| Sign along the western road announcing the closure for crabs |
You might know that Anne is a crab geek, not surprising
since she spent nearly twenty years doing crustacean research for the State of
Florida. And Chris likes to eat crabs. So, we were intrigued by the signs we
saw on Providencia regarding the black land crab
Gecarcinus ruricola. Travelling in the Caribbean, you’ve probably
seen the holes that these crabs occupy in forested areas, often far from the
water, or wondered W.T.F? upon finding a crab claw high up a mountain. They’re
also often found in the market or on the menu if you want a taste. The species
is nocturnal, and their skittering about in the dark, clicking across a road or
rustling through the undergrowth, can be unnerving if you don’t know what it
is. Anyway, it’s precisely these wanderings that bring attention to the crab
during mating season. Though terrestrial as adults, larval development occurs
in the ocean. Adults migrate from the forest to the ocean to spawn, then back
to the forest. Initial larval development occurs at sea, then megalopal-stage larvae
(looking mostly like little crabs at this point) migrate back ashore and head
to the forest. And these are not small migrations; the population on
Providencia was estimated at three million. If a road lies between forest and
ocean…well, you can imagine the mess. Consequently, from April 1 to July 31, a
portion of the road that runs along the western side of Providencia is closed
to all vehicles. Since the road around the island is a loop, this means a lot
of detouring back around the eastern side of the island. Time-consuming,
perhaps, but it’s done for the purpose of conserving the species, which is good
thing. They show a film of the black land crab migration at the Lighthouse
Café/Cinema/Art House,
but we unfortunately didn’t make it. Fellow crab geeks can find detailed analyses
of black land crab
population biology
and
reproduction
on Providencia and San Andrés in these articles from the Journal of Crustacean
Biology. And if you want to feel a little squirmy, check out this
video of migrating adult
and larval red land crabs (related species) on Christmas Island – not the exact
species as on Providencia, but related, and the same general idea.
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| Crab information alongside the trail to the Peak |
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| Crab migration documentary at the Lighthouse |
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| The black land crab is even featured at a bus stop |
