Leatherbacks have a global distribution and have been found as far north as Newfoundland and northern Norway. They undertake the long journey from the tropical and subtropical nesting beaches to the cold northern waters in search of dense aggregations of jellyfish, their main prey. Tags applied to leatherbacks nesting on the Caribbean coast of Costa Rica have been returned from Florida, North Carolina, Delaware and even Spain.
In spite of their wide distribution, the number of leatherbacks continues to decline. Some researchers now believe that the leatherback may become extinct in the next few decades if current threats to the species are not alleviated. Unsustainable harvest of eggs and incidental catch in net and long-line fisheries are the main reasons for their decline. Killing of adults for meat, destruction of nesting habitat and ingestion of plastics often mistaken for jellyfish also contribute to shrinking leatherback populations.
Although the killing of subadult and adult individuals has the greatest impact on leatherback populations, extensive egg harvest alone can result in population eradication. The best documented example of the effects of excessive egg harvest is that of Terengganu, on the east coast of peninsular Malaysia. In the 1950’s, more than 10,000 leatherback nests were deposited on the Terengganu beaches, but in 1995 only 37 nests were recorded along the same stretch of beach. A long history of systematic egg harvest is believed to be the major cause of this decline.
Leatherbacks show less nest site fidelity than other species of sea turtles. The leatherback turtles crawling ashore in Tortuguero, Pacuare, Mondonguillo, Matina and Gandoca-Manzanillo (all in Costa Rica) and even Bocas del Toro, Panama and southern Nicaragua may therefore belong to the same population. Illegal egg harvest is substantial on many parts of this coast, and in some places every egg is taken. In Panama, poachers in search of eggs kill leatherbacks before they nest.