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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans > Superfamily Ocypodoidea
Horn-eyed ghost crab
Ocypode ceratophthalmus
Family Ocypodidae
updated Dec 12

if you learn only 3 things about them ...
They only seen at night. But the large holes to their burrows are commonly seen on sandy shores near the high water mark.
Their burrows are deep. Don't try to dig them up.
They can move very fast.

Where seen? This large but elusive crab is common on many of our shores. Yet, it is hard to spot. It probably got its common name because it is active only at night, and it moves so swiftly over the sand that you usually literally only get a ghostly glimpse of one.

Often all you will see of the crabs during the day are their large holes marking the entrance to their burrows . These are usually on sandy beach near or above the high water mark.
It is said that when tunneling out their burrow, the crab carry sand to about 50-100 cm away from the burrow entrance, then toss the sand as far as it can. This behaviour probably explains the typical "spray" pattern of sand around the burrow. The burrow can be quite deep. So please don't try to dig up the crab.

Features: Body width 6-8cm. Body squarish box-like. Usually bluish grey with brown markings on the back, often in the shape of an "H". But a variety of other patterns also seen. Pincers long, downward pointing often with white or pale claws. Has a vertical ridge on the inside of the 'palm' that produces a rasping sound when rubbed against the rough surface of the face. This is probably done to declare their territory. Legs long with pointed tips. Large eyes on short stalks which can fold away into grooves on the body when the crab burrows into the sand. Adult crabs have a characteristic tall skinny point or 'horn' on top of each eye (called the stylophthalmous), usually darker in colour. The horn is shorter in females and absent in juveniles (2.5cm or smaller). A study found that juveniles can change their body colour and pattern to match the surrounding sand, usually becoming lighter during the day and darker at night.

Ghost crabs are well adapted for life out of water and are among the few marine creatures that roam the beaches at low tide, particularly at night. They run rapidly on the sand and can burrow quickly into wet sand. They can stay for a long time away from the sea because they can absorb water from the wet sand through special hairs on the base of their legs by capillary action.

Similar to the Smooth-eyed ghost crab (Ocypode cordimanus) which is rarely encountered.

Speedy Ghosts: Ghost crabs can really run fast! As suggested by their scientific name ("Ocy" means swift and "podi" foot in Greek). They literally fly over the sand and their movement has been described as a small leaf blowing over the sand surface. In fact, they may be among the fastest land creatures, moving at 100 bodylengths per second. In comparison, the cockroach does 50 bodylengths while the cheetah does a sluggish 10 bodylengths. Ghost crabs are only beaten by tiger beetles which do 171 body lengths when they are really scared. Being fast moving creatures, Ghost crabs have excellent eyesight to see where they are going.

What does it eat? At low tide, this scavenger is very active at night, scurrying everywhere on the shore. It has been seen eating all manner of recently dead animals on the shore from fireworms to fish, shrimps and even other crabs. It may also hunt small animals and clams and snails near the water's edge. Near the flotsam left on the high water line, we can also sometimes see little scratch marks probably made by ghost crabs checking the line for edible titbits.


Raffles Lighthouse, Jul 06


A slot on the body for
the eye stalk to 'fold' away.
Tanah Merah, Aug 09


Vertical ridge and tiny bumps
on the inside of the 'palm'.
Tanah Merah,
May 11


Typical burrow near the high water mark.
Changi, Apr 05

Some have white pincers,
one much bigger than the other.
Sisters Islands, Jan 06

No 'horns' on the eyes: young one?
East Coast, Jun 06

Eating a shrimp.
Tanah Merah, Aug 09

Eating a fireworm.
Changi, Apr 09

Eating another crab.
Pulau Hantu, Nov 03

Eating a fish, probably a goby.
Tanah Merah, Sep 10

Horn-eyed ghost crabs on Singapore shores
Photos for free download from wildsingapore flickr
Distribution in Singapore on this wildsingapore flickr map

video clips and more photos of horn-eyed ghost crabs on Singapore shores

Links

References

  • Ng, Peter K. L. and Daniele Guinot and Peter J. F. Davie, 2008. Systema Brachyurorum: Part 1. An annotated checklist of extant Brachyuran crabs of the world. The Raffles Bulletin of Zoology. Supplement No. 17, 31 Jan 2008. 286 pp. (Online PDF on the Raffles Bulletin of Zoology website)
  • Jones Diana S. and Gary J. Morgan, 2002. A Field Guide to Crustaceans of Australian Waters. Reed New Holland. 224 pp.
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