Demography and natural history of the land crab <i>Gecarcinus ruricola</i> Linnaeus, 1758 (Decapoda: Brachyura: Gecarcinidae) in northern Puerto Rico

Abstract The land crab Gecarcinus ruricola (Linnaeus, 1758) inhabits coastal forests in Puerto Rico. It is rarely seen, and was designated as a vulnerable species by the Government of Puerto Rico. Despite its vulnerability, there are no previous empirical or natural history studies of this species in Puerto Rico. We studied the natural history and demography of the species and offer recommendations for the conservation and management of the population of the species at the Reserva Natural Hacienda La Esperanza (RNHLE) in Manatí, northern Puerto Rico. We monitored the population in two sampling periods between 2016 and 2020. We captured, sexed, measured carapace width, and marked and released crabs to estimate sex ratio, size distribution, abundance, movement, and viable population size, as well as making observations in nature. The 305 captured crabs presented a 1:0.3 sex ratio, which was biased toward males. Male crabs are larger than females, and there was a difference in carapace width between sampling areas within the reserve. Population abundance estimation was 608 individuals, most of which exhibiting site fidelity. The viable population size estimate indicates a reduction after two hurricanes in 2017. Even though crabs in the RNHE are larger than in any other area in the Caribbean, the population size is small and at risk of extirpation, given the small number of females captured and the low viable population size. Even though G. ruricola is a protected species in Puerto Rico, this study’s findings suggest that the species vulnerable classification by the Puerto Rico Department of Natural and Environmental Resources needs to be revised.