Caribbean Compass Yachting Magazine - November 2021

GET TO KNOW YOUR CARIBBEAN MARINE LIFE
CARIBBEAN CRABS
Part 1 - The Landlubbers
by Darelle Snyman
A large variety of these crusty characters call the
Caribbean islands and their fringing reefs home. This is
another group of critters that I enjoy encountering while
snorkeling or exploring the shore. There are just too many
of these clawed creatures to adequately cover within the
scope of these articles; therefore, I focused on the ones I
love to observe.
The Atlantic Ghost Crab
A little shore crab that definitely needs no introduction
is the swift-footed Atlantic Ghost Crab (Ocypode quadrata).
It is fun watching these cute characters scurry across the
sand in a somewhat purposeful manner, just to disappear
into their burrows in the blink of an eye. They are
amazingly fast and can move up to 16 kilometres or ten
miles per hour. The pale color of these nimble critters
allows them to blend in perfectly with their sandy
environment, hence the common name Ghost Crab. The
ability to change color also assists these masters of
camouflage to seemingly disappear from view.
They are industrious burrowers and can create an
extensive network of tunnels up to four feet deep, where
they spend most of their time during the day to stay cool
and safe from the predatory eyes of gulls. Even though
they have adapted to a terrestrial lifestyle, they still have
to keep their gills moist in order to breathe. That is why
you will often see them making a stand at the shoreline,
holding on tightly to the sand as the waves wash over
them. They are also able to use the hairs on their legs to
wick moisture from the damp sand onto their gills.
These boxy-shaped crabs are easily recognized by their
prominent stalked eyes, which give them a 360-degree
view of their world. You can find them out and about
during the day, but it is when dusk settles in that they
become most active, foraging for food, doing home repairs
or seeking a mate.
They can live up to three years and mate right
throughout the year. The female carries the eggs under
her body until they are ready to be released into the water.
During this time she makes frequent trips to the water’s
edge, as the eggs need to be kept moist. If you see a ghost
crab floating upside down, it is mostly likely a female
ghost crab ventilating her eggs. This ability to float upside
down has only been endowed to the female of the species.
Members of a ghost crab family communicate by making
a variety of sounds. Their acoustic skills include striking the
ground with their claws, making a bubbling sound, and
producing a squeaky sound by rubbing a series of ridges on
their claws together, a process known as stridulation.
These beach-dwelling omnivores feast on carrion and
are aggressive predators of sea turtle eggs and hatchlings.
The poor turtle hatchlings get dragged down into the
crab’s underground lair where they are devoured. In
addition to feeding on baby sea turtles these crabs also
like to eat mole crabs, beach fleas and coquina clams.
They can also obtain nutrients by passing sand through
their mouthparts and extracting nutrients from the algae
in the sand; this is known as “deposit feeding.”
The Mudflat Fiddler Crab
Another adorable semi-terrestrial little crab with attitude
is a cousin of the Ghost Crab — the Fiddler Crab. The
Mudflat Fiddler Crab (Uca rapax) is a common sight in salt
marsh and mangrove areas; they are often seen in very large
numbers. They make small holes in the sand or mud and
an occupied hole will have sand or mud pellets scattered
around the burrow opening, indicative of its occupancy.
—Continued on next page
The Black-Backed Land Crab gets its French nickname, tourlourou, from soldiers who wore blue jackets
with bright red trousers.
The male Fiddler Crab waves his single large claw at a female like he is playing the fiddle,
hence the common name.
The pale color of the Atlantic Ghost Crab allows it to blend in with its sandy environment.
NOVEMBER 2021 CARIBBEAN COMPASS PAGE 31