Western Ghost Crab
The Western Ghost Crab has a limited distribution range being only found on the WA coast between Bunbury and Exmouth Gulf, including Barrow Island (WA). The type locality is Dirk Hartog Island, Shark Bay.
The Western Ghost Crab is a large, distinctive, golden-coloured Ghost Crab. It has a deep, square-shaped and robust body, with strong running and digging legs. It grows to a carapace width of 45 mm. Its eyestalks do not have a tall terminal spike, like the Horn-eyed Ghost Crab, Ocypode ceratopthalma. In an adult male one chelae may be much larger than the other chelae. Across the carapace and chelae and legs there are many spines and bumps. On the inside of the palm of claws is a rasping ridge consisting of 10-25 rounded knobs. There is no record of the sound that this species of crab might make. Male Western Ghost Crabs are slightly larger and have larger chelae than the females have.
This crab is mostly cream in colour with a strong golden tinge. There are faint brown markings on the carapace. The chelae are rich golden yellow.
Ecology/Way of Life:
The Western Ghost Crab occurs on sandy ocean beaches. During the day they are usually in their burrows that they dig at high tide levels and beyond, to 12-20 metres from the water. The burrows are near vertical with simple openings. The bottoms of the burrows usually seem to be south of the entrance. This may be to stop sunlight from shining down the burrow. The sand they dig from the burrow is carried away and dispersed randomly. During night they forage along the strand lines of the beaches for scraps of food.
There is a record from 1962 where Ride reported from Bernier Island that adult O. convexa were foraging over half a kilometre inland following heavy rain. This ability to withstand heavy immersion in freshwater and forge in wet vegetation may also occur in the other Ocypode species.
Where the Common Ghost Crab, O. cordimana and the Western Ghost Crab, O. convexa, occur together at North West Cape, WA, the latter occurs higher up on the beach, in more dry, sloping areas.
When trying to get a photograph of an adult male, it would not stick both of its eyestalks up at the one time, but lay the other down in its protective channel. This may be to protect at least one eye from being bitten off by a predator.
Interaction with Humans/Threats:
The Western Ghost Crab has a very restricted range in Western Australia. If there were a major environmental disaster, where an oil spill covered a large area of coastline, then pockets of this species could be threatened. Fortunately, it occurs in regions where there is sparse human habitation.
Ocypode convexa, Quoy & Gaimard, 1824. Ocypode comes from the Latin octo, meaning eight and pode the Greek word for foot. Convexa comes from the Latin words con- and vehere, meaning to carry. Its modern use is to rise into a round form on the outside, the reverse of concave.
Davey, K. (1998) A Photographic Guide to Seashore Life of Australia. p.61, New Holland Press, Sydney.
George, R. W. & Knott, M. E. (1965). The Ocypode Ghost Crabs of Western Australia (Crustacea, Brachyura). Jour. Royal Soc. W. A. v.48(1), 15-21.
Jones, D. & Morgan, G. (1994). A Field Guide to Crustaceans of Australian waters. p.196, Reed.
Ride, W. D. L. (1962). In Bernier and Dorre Islands. W. Aust. Fish. Dept., Fauna Bull. No. 2; 1-131.
Text, map & photograph by Keith Davey.
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