Here is another post about critters found in Los Cabos, Mexico. These neat little ghost crabs (Ocypode sp.) were common on the beach outside my hotel. And little they were—a big one would have a carapace that wasn’t much more than six or seven millimetres across. These crabs dig burrows in the sand to escape the heat of the sun and predators. Some areas of the beach were dotted with holes and as you walked along these tiny crabs would literally fly across the sand and down into their burrows. They were amazingly fast and as you can see from these photos, they were extremely well camouflaged against the sand. If their burrow wasn’t close enough when they felt threatened they would dash away and then suddenly freeze and seemingly disappear. It was fascinating how similar their appearance and behaviour was to the sand spider I wrote about in an earlier post (How to photograph an invisible spider). These two very different species—one a marine crustacean, and the other a terrestrial arthropod—have evolved very similar strategies for survival on a sandy substrate.
Of course as soon as I saw these little crabs I had to photograph them! I spent a great couple of hours squirming across the sand on my belly trying to get close enough to take some good photos. I’m sure it looked rather comical, but it was really too much fun! I didn’t have a close focussing long lens with me, so my only option was to use the 35 mm macro and figure out a way to get within a few inches of these little critters.
I eventually worked out three different techniques:
(1) The easiest thing to do was to watch into which hole a crab darted down, then lay down on the sand, focus on the hole and wait…Hopefully the crab would eventually emerge to have its picture taken. This technique worked, but the crabs always took a long time to re-emerge; and when they did they would often take one look at me and dart back down their burrow. I got some nice pictures, but it was pretty boring.
(2) Although most of the crabs would hide in their burrow as soon as I came along, I came to realize that there was always one or two that didn’t seem to have a burrow ready. They would stick to the dash and freeze behaviour. I found that if I kept slowly following them (crawling along the sand) I could sometimes get closer each time they froze, eventually managing to get within inches. I got some very nice photos this way—just from pure persistence.
(3) My third mthod was a combination of the previous two. I discovered that if you followed a crab that didn’t have a burrow long enough, they would sometimes give up on the “dash and freeze” tactic and head down another crab’s burrow. If I then followed technique #1, in a very short time the owner of the burrow would evict the interloper. Not only would both crabs emerge onto the sand, but the burrow owner would be so focussed on the interloper that neither would pay much attention to me.
All of these photos were taken with available light, and in the bright sunshine I was able to shoot with fast shutter speeds to freeze the crab’s movement while using reasonably small lens apertures to maintain decent depth of field.
Normally I am not one to much enjoy just laying on a beach in the sand. But crawling around on the beach chasing crabs…now that is my idea of a fun vacation!
The technical stuff:
Camera: Olympus E-620 digital SLR
Lens: Zuiko 35mm macro
Settings: manual exposure (F11 @ 1/250 sec)
Lighting: Available light