International Journal of Pure and Applied Zoology

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Long-Term Sedentary Behavior Of Coconut Crabs In Their Northernmost Range

Movement of the coconut crab Birgus latro was investigated at the Ocean Expo Park in Okinawa Island, Japan, the northernmost range of this large, terrestrial crustacean. Recapture data were obtained using photographic matching of carapace groove patterns to identify individuals. Of the 485 crabs captured and photographed, 122 were recaptured and the distances they moved were recorded during an eight-year study period. Monthly changes in the sex ratios of crab populations at shore and inland areas indicated that females and a few males moved to the shore area during the reproductive season. On average, 69% of males and females did not move more than 200 m from their release points regardless of the duration of the liberty period. Long distance movements were not common. Differences in size and sex did not correlate with the distance moved. These observations indicate that coconut crabs have a highly sedentary lifestyle and that they remain in their home ranges for many years while repeating their homing behavior. The data suggest that coastal forests, which provide a corridor for migration, are important for crab conservation.

Author(s): S. Oka*, K. Miyamoto, and S. Matsuzaki