Experiment on Time Spent on Surface
This experiment was undertaken from 1:30 to 4:00 pm at ebb tide on four consecutive
days in the field. For each Uca species, six to eight large-size male crabs were observed
each day and the observations repeated three to five times for each individual. Crabs
were not marked and new or the same crabs might have been observed on successive
days. The time taken for each crab to emerge from its burrow and return underground
was measured to the nearest second using a stop watch. Air and sediment temperatures
were measured with a thermometer, and the relative humidity with wet and dry bulb
thermometers and reference to a Relative Humidity Table.