Black Land crabs are members of the family Gercarcinus ruricola. The adults live on land, though their dependence on water varies between species. Once mature, females migrate annually to the sea to breed. Near the sea they lay their eggs, incubate them for about two weeks, and then enter the sea briefly for the larvae to hatch. The larvae released into the sea must drift and develop for about twenty days, and if the currents have been favourable, those that are lucky to survive come back to shore to migrate inland to continue their life cycle. Both the adult migration from the island's interior to the shore and the mass landing of juvenile crabs and their migration back inland is a phenomena that needs to be experienced first hand.
The collection of black land crab for personal consumption and/or consumer markets has long been a traditional activity among San Andres Archipelago islanders. However, the Free Port designation of San Andres has increased the use of the Archipelago as a tourist destination, which together with the immigrant influxes that have drastically increased the local population, have all contributed to an increased level of exploitation of this resource. This is seemingly verified by local concerns that crab populations are declining alongside catches, this being linked to an increase in catcher numbers as well as market demand. Increased road traffic and changing agricultural practices, including construction activities, are also seen as activities that have impacted negatively on crab numbers. From April 1st until July 31st, the reproductive period of the Black Crab takes place. The catchment, consumption and sale of this crustacean are banned during this period.