Status of coconut crab <i>Birgus latro</i> (Linnaeus, 1767) in Nicobar Island

Coconut Crabs Birgus latro (Linnaeus, 1767) is the largest living terrestrial arthropod, listed as Vulnerable in the IUCN red list. In this paper, we described the existing condition of distribution, population, and measurement of morphometric traits of coconut crabs, as well as the management recommendations to prevent the over exploitation of coconut crab population. Intensive and extensive surveys were carried out at 52 sites in the Nicobar group of Islands (Great Nicobar Island, Little Nicobar, and Nancowry group of Islands) and Little Andaman during the period of April 2015 to March 2018. Transect survey and bait station survey methods were used for the determination of population density of coconut crabs, Catch Per Unit Effort (CPUE), respectively. A total of 103 coconut crabs were recorded during the survey and reveals that the sex ratio of crabs was observed as 1: 0.6. The average Thoracic Length (TL) of female coconut crab was measured as 32.0 ± 8.7 and 37.9 ± 13.5 for the male coconut crab. Estimation of size class of coconut crabs was observed as 76% of female and 59% of males are greater than 25 mm of TL and less than 50 mm. Furthermore, hardly 24% of male crabs were with greater than 50 mm of TL. The study discloses that the Catch Per Unit Effort (CPUE) of one crab per bait corresponds to a population density of 4.6 crabs/km2, and the male coconut crab was dominated in size as well as population in Andaman and Nicobar Islands. The study concludes that, the factors like differences in body size, availability of natural foods, disturbance level and environmental conditions suitability could influence in character size. The current study perceived that, the population of coconut crabs are declining due to the harmful anthropogenic activities such as habitat destruction and hunting. Eventually, we recommend management strategies for the prevention of overexploitation of coconut crabs and the conservation of coconut crabs along with its natural habitats.