Sunday, June 13, 2010
St. Croix - Crabs
Hermit crabs, also known as soldier crabs (Coenobita clypeatus), are abundant on St. Croix. It seems almost every stucco wall has a hermit crab traversing its surface, or scurrying along the bottom edge. In the evening, if you stop near some brush, you can hear the clicking of hermit crabs bumping into their surroundings and each other.
Sometimes they approach the water's edge in order to feed. This particular afternoon, the beach was teeming with them, and I picked up a handful.
Walking along the beach, ghost crabs (Ocypode quadrata) can trick your eyes. Was that a bit of sand or dust, or an animal? They move at startling speeds, can change direction in an instant, and are usually not far from a burrow. I did manage to catch a few small ones, though.
One of my favorite crustaceans is the mole crab (Emerita sp.). I've found them at almost every beach I've visited, from the North Eastern coast of the U.S., to Florida, to various islands in the Caribbean. They are small and round, hardly resembling crabs at all (they are in the same order, Decapoda, but a different infraorder). They live right at the shoreline, where the waves are crashing and receding. There they burrow backwards just deep enough so that their antennae can reach into the water to capture passing plankton. These antennae can be a give-away to their presence, as you can see the "V" shaped ripples they leave as the waves recede. On beaches with rockier sand, like where we were, they can be more difficult to detect. Then it comes down to lucky guessing by digging into the sand. You need to be careful, though, that they do not hear you coming. The mole crabs will dig deeper or change positions if they can feel your footsteps nearby. I find digging up mole crabs to be a great trick when there are curious children on the beach. This time, there were none around, but I got to teach my best friend how to catch them.