Field Guide to Fort Myers Beach: Atlantic Ghost Crab

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I have no doubt that everyone on Fort Myers Beach has seen these crabs at least once, if not hundreds of times crawling around in the sand or scurrying off to hide in one of their numerous tunnels that they dig to hide from predators.

Atlantic Ghost Crabs are native to the whole state of Florida. They can be found as far south as Bermuda and as far north as Rhode Island.  Ghost Crabs get their names from their grey to sand colored shells, which provides great camouflage for hunting and hiding from predators. Occasionally the crabs must return to the water in order to moisten their gills or they will gather water from wet sand from the hairs on their legs and transfer the water to their lungs.

If their gills are not wet they cannot breathe properly and will die. Their eyes are up on stalks that allow for the crabs to see in any direction around their body. Male Ghost Crabs have small horns at the top of their eye stalks which is the only external way to tell the two genders apart.

Atlantic Ghost Crabs are more active at night, although they are not completely nocturnal. Most feeding occurs at night and ranges from plant material, clams, insects, and eggs.

During shorebird and sea turtle nesting season Ghost Crabs will eat bird eggs as well as bird chicks and sea turtle hatchlings. Ghost Crab tunnels are very important for the survival of the ghost crab. During the heat of the day it is very easy for the crab to become overheated, as it is cold blooded, and is more likely to be seen by predators.

Ghost Crabs will hide in these holes for most of the day until it becomes darker and cooler outside. Their boroughs are up to four feet deep and often have two openings. That way if one opening collapses they still have an exit route for them to be able to get out of their tunnel. The younger crabs tend to excavate their holes closer to the water’s edge and the older crabs will be up further away from the water.

Now one would think that since a Ghost Crab’s borough is so important to it, it must lay its eggs in there too.

That’s only half right, but I was pretty shocked when I found this out to so don’t take it too hard. It turns out that once a year, right after a female has just finished shedding her shell (all crabs have to do this in order to grow, however a female can only get her eggs fertilized after she sheds her shell) the males nearby can sense this and start to fight over her.

After the strongest male crab wins it’s duel and the loosing male runs away the male fertilizes the female’s eggs in the borough and the female holds the eggs under their bellies and once the eggs are ready she will travel to the water’s edge and release her eggs into the ocean.

There the larvae develop until they have grown into their adult crab stage. The larvae travel even further than the range of its parents. Some being found as far north as Massachusetts – which is a much colder climate than the adults can take.

 

Rae Blake, Environmental Technician
Town of Fort Myers Beach