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Burrows of the ghost crab Ocypode quadrata (Fabricius) are widespread in beaches of Texas and Georgia. The orientation of these burrows and the factors that influence it are potentially useful in recognizing and interpreting ancient beach environments, shoreline position and orientation, and direction of dominant winds.
O. quadrata burrows generally slope downward away from the shoreline with branches being landward of the main shaft. This preferred orientation is controlled by the direction of onshore winds. During the short excavation period (several minutes), individual crabs burrow 45° to either side of the local downwind direction. The mean orientation of all ghost crab burrows over days or larger periods of time, however, corresponds to the mean onshore wind direction.
Other factors that influence burrow orientation include temperature and local landforms. When air temperatures drop below 15.5°C, ghost crabs generally stay in their burrows and reduce their activity. In Texas and Georgia, winter winds of these temperatures are generally offshore winds and consequently have little effect on burrow orientation. Where fore-dune ridges exist, burrows are randomly oriented in the interdune flats owing to wind shadows. In other places, mean burrow orientation is parallel with geomorphic features such as swales which tend to funnel the wind in specific directions.
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