DNA Analysis Solves 250-Year Mystery of Seychelles' Vanished Crocodiles
Museum specimens reveal the extinct reptiles were saltwater crocodiles that drifted 3,000 kilometers across the Indian Ocean before being wiped out by settlers.
Scientists have finally solved a centuries-old mystery about crocodiles that once thrived in the Seychelles islands but disappeared shortly after human settlement began in 1770. Using DNA extracted from historic museum specimens, researchers determined that the vanished reptiles were not a unique species as some had suspected, but rather an isolated population of saltwater crocodiles that had traveled thousands of kilometers across the Indian Ocean.
The genetic analysis, conducted by researchers from Germany and the Seychelles, compared mitochondrial genomes from preserved Seychelles crocodile specimens with DNA from modern saltwater crocodiles across their range. The study confirmed that the island population was closely related to Crocodylus porosus, the world's largest living reptile and one of the few crocodilian species capable of long-distance ocean travel.
Early explorers' accounts described crocodiles as common sights along Seychelles shores for more than 250 years before permanent settlement. However, within approximately 50 years of human colonization beginning in 1770, the entire population had been completely exterminated. The rapid extinction likely resulted from hunting pressure and habitat destruction as settlers established permanent communities on the previously uninhabited islands.
The research revealed that the founding crocodiles must have drifted at least 3,000 kilometers across the Indian Ocean to reach the remote archipelago, possibly traveling much farther depending on their origin point. Saltwater crocodiles possess specialized salt glands that allow them to survive extended periods in seawater, enabling the species to spread across vast oceanic distances and colonize remote islands throughout the Indo-Pacific region.
Before the Seychelles population was eliminated, saltwater crocodiles occupied an enormous range stretching more than 12,000 kilometers from Vanuatu in the Pacific Ocean to the Seychelles in the Indian Ocean. The genetic evidence suggests these far-flung populations remained connected over long periods through the species' remarkable ability to traverse ocean barriers, making the Seychelles crocodiles one of the westernmost populations ever documented.
