Studies on the ecology and behaviour of the ghost crab, <i>Ocypode cursor</i> (L.) in northern Cyprus

Abstract

SUMMARY: Aspects of the ecology and behaviour of Ocypode cursor were studied on the beaches of Northern Cyprus. The crabs were widely distributed around the north coast of the island, occurring on 68 of the 77 sandy beaches investigated. At the main study beach at Alagadi, crabs occupied a band approximately 12 m wide; starting approximately 3 m horizontally from the edge of the sea (tidal fluctuation was minimal). Most small burrows occurred near to the sea, with the burrows of larger crabs predominating higher up the beach. Burrow numbers varied during the summer which was mainly attributable to variations in the numbers of burrows of juveniles. The sex ratio of emergent crabs also varied during the summer, possibly reflecting burrow oriented behaviour of reproductive females. There were strong correlations between burrow diameters and carapace lengths of the occupant crabs. There was a positive correlation between the presence of crab burrows and the number of people using sections of beach. The crabs were principally nocturnal, benefitting from food discarded by tourists. They also scavenged animal carcasses and were active predators of turtle eggs and hatchlings. Crab burrows usually had a single opening oriented towards the sea and those cast were L-or J-shaped. Burrows did not penetrate to the water table. The water content of the sand at the bottom of burrows was around 14 % by weight. Their burrows in the well-sorted sand provided the crabs with a thermally stable environment.

Vertical distribution by demographic groups of ghost crab Ocypode quadrata (Crustacea: Brachyura)

“…These data differ only from the observations by Branco et al (2010) at Praia Brava (Santa Catarina, Brazil), who caught females of O. quadrata in higher densities during several months of the year. Similar results were found in several other studies of ocypodid populations (Milne & Milne 1946;Strachan et al 1999;Negreiros-Fransozo et al 2002), which according to Milne & Milne (1946), are usually skewed toward males. However, according to Trott (1998), in these crabs mating may be polygamous, favoring females, because normally this group prefers the intertidal zone and males remain in the upper portion.…”

Number of ghost crab burrows does not correspond to population size

“…Their sample did not display any sex ratio disequilibrium (χ 2 =1.758, df=1, P>0.18; statistics not published in the original article). Since ghost crabs are primarily nocturnal [29,30] and our study was conducted during daylight hours, our results raise questions about the possible explanations for the observed ratio. Crabs are believed to be in their burrows during daylight hours, but we could not find them, suggesting that there are alternative daytime locations.…”

New Mediterranean Biodiversity Records (November, 2016)

“…10) (Relini, 2009;Froglia, 2010). In the Mediterranean Sea, amateurs and researchers recorded the species in the eastern part: Israel, Turkey, Greece and Cyprus (Strachan et al, 1999). Recently, the species was recorded in Malta (Times of Malta, 2016).…”