Threats
Ghost crabs can be injured or killed through human activities such as four-wheel driving along sandy beaches (Moss and McPhee 2006), mechanical beach-cleaning (Noriega 2008), trampling of sand and dunes (Lucrezi et al. 2009 and 2009), and through the impacts of erosion control measures, urbanisation and coastal development, and climate change (Jones et al. 2007; Schlacher et al. 2007; Schlacher et al. 2010).
Four-wheel driving along sandy beaches, particularly at night when ghost crabs are most active, crushes and injures or kills a significant proportion of individuals along the intertidal and supralittoral zones (Wolcott and Wolcott 1984; Moss and McPhee 2006; Schlacher et al. ). During the day, the weight of recreational vehicles and mechanical beach-cleaning devices can destroy burrows and kill or injure the occupants (Schlacher et al. 2007; Noriega 2008).
Frequent human trampling of sand and dune habitat can lower the density and change the distribution of ghost crab burrows along the beach gradient, destroy burrow entrances and undermine the sand structure threatening burrow stability (Lucrezi et al. 2009). Mechanical beach-cleaning may reduce levels of ghost crab prey forcing crabs to shift foraging away from intertidal and supralittoral zones to more landward dune habitat ( ). Although ghost crabs feed opportunistically, and dune habitat could provide sufficient food resources, juveniles are more vulnerable to the effects of dehydration than adult crabs and require more frequent access to seawater to moisten gills (Schlacher et al. 2011). Through moving from their natural intertidal foraging zone to dune areas, juveniles may also be more susceptible to cannibalism by adult Ocypode species that are more abundant in the dunes ( ).
The increasing migration of humans to coastal areas is fuelling seashore development and destroying ghost crab habitat, for example through the replacement of sand dunes with parks and infrastructure such as barbecue facilities and shower amenities (Schlacher et al. 2007; Noriega 2008). The construction of sea walls and shoreline armouring, to counteract erosion and the landward migration of the shoreline, can block the movement of ghost crabs to dune habitat thus removing a source of refuge and increasing the effects of human disturbances along the intertidal zone (Jones et al. 2007; Lucrezi et al. 2008; Noriega 2008).
Climate change threatens the existence of sandy beaches and is therefore a potential threat to ghost crabs (Jones et al. 2007). This threat could be manifested in sea level rise, increased storms and storm surges, and the breakdown of interactions among beach and adjacent habitats (Jones et al. 2007). |