The relationship between the sensorial system of the predator and the signals that the prey sends is an unexplored field in science. In the case of the land crabs, the most outstanding characteristics to the predators are the size of the chelae and carapace which are also fundamental for survival and reproduction. Crabs invest energy in growth of chelae and carapace which might have a benefit for survival and reproduction but at the same time this growth could influence the attraction to predators. The objective of this project is to investigate if there is a relationship between the size of the carapace and the mortality of land crabs. I visited four different coastal zones in Puerto Rico inhabited by land crabs; there I collected dead crabs carapace, identified the species and measured carapace width and the openings in the dorsal part of the crab which are the result of bird’s attacks.
Results/Conclusions
A total of 96 carapaces were collected representing five different species of crabs. The most abundant size class was 70 to 79 mm category. Forty six percent (46%) of the carapace possessed holes that measured between 10 to 14 mm wide. The Birds are selecting large land crabs. Humans also preferred large land crabs and these are also the sizes that harvesters capture in Puerto Rico. The results confirmed that the populations of crabs in Puerto Rico are suffering a double predation; by its natural predator as much as by humans through commercial exploitation; which causes a marked decline on the land crab population. Land crabs are protected in Puerto Rico however, the protected crabs and the Sizes that suffer the most natural predation, are not in the sizes protected (under 64 mm carapace width) by the Fishery Rule of the Department of Natural and Environmental Resources of Puerto Rico. This marked decrease, could cause changes in the ecosystems and secondary effects in other species and in the habitats.
