Seasonal variation in the land hermit crab, Coenobita rugosus H. Milne Edwards, 1837 (Decapoda, Anomura) and a preliminary study of land hermit crabs as a bioindicator of turtle nesting at Penghu County Wang-An Island green turtle nesting refuge, Taiwan

The present study surveyed the land hermit crab species, body size, shell type, and shell suitability, at five sites over four seasons in the Penghu County Wang-an Island Green Turtle Nesting Refuge. Coenobita rugosus H. Milne Edwards, 1837 was the only species recorded and found at three sites (Tiantai Hill, Xi’an Reservoir, and Tudigong). The density index of hermit crabs exhibited notable variations across the sites, showing no significant variation with the changing seasons. The bush habitat displayed a higher density index compared to the sand habitat. Additionally, the sites differed significantly in terms of the shell type and body size of the hermit crabs. Further, no significant relationship was established between abundance and weather factors or between crab abundance and sea turtle nesting. This investigation is a preliminary examination of the possibility of land hermit crabs being used as bioindicators for breeding of sea turtles.