Saltwater crocodiles can grow to more than six meters in length and weigh over a metric ton, making them among the largest and heaviest living reptiles in the world. (Kathrin Glaw via SWNS)
By Stephen Beech
Saltwater crocodiles swam thousands of miles across the Indian Ocean to survive, new research suggests.
Accounts from early expeditions to the Seychelles more than 250 years ago described the deadly predators as common along the coasts of the archipelago.
But after the first settlers established a permanent presence in 1770, the Seychelles crocodiles were completely wiped out within 50 years.
Now, a new genetic study shows that the crocodiles on the remote Seychelles islands did not belong to a separate species.
The three incomplete skulls from the Seychelles National Museum are among the few preserved remains of the Seychelles crocodiles. (Kathrin Glaw via SWNS)
Instead, they represented the westernmost population of the saltwater crocodile (Crocodylus porosus).
The findings, published in the journal Royal Society Open Science, confirm an earlier hypothesis that had been based solely on external characteristics.
For the new study, scientists from Germany and the Seychelles examined the evolutionary history and distribution of the saltwater crocodile by comparing its DNA sequences.
(Photo by Likeboss lertpongsaporn via Pexels)
They combined genetic data from modern samples with mitochondrial genomes from historical museum specimens of the genus Crocodylus, including material from the Seychelles crocodile, which disappeared around 200 years ago.
Among all living crocodiles, scientists say the saltwater species is the best adapted to life in the ocean.
For example, special salt glands allow it to excrete excess salt and survive for long periods in seawater.
Researchers say that enabled the species to colonize islands and coastal regions over thousands of miles.
A subadult saltwater crocodile basking in the Nilgawa River, Sri Lanka. (Kathrin Glaw via SWNS)
Study senior author Dr. Frank Glaw, from the Bavarian State Collections of Natural History (SNSB), Germany, said: "The founders of the Seychelles population must have drifted at least 3,000 kilometers across the Indian Ocean to reach the remote archipelago, perhaps even much further."
First author Stefanie Agne, a doctoral student at the University of Potsdam, Germany, added: "The genetic patterns suggest that saltwater crocodile populations remained connected over long periods and across great distances, pointing to the high mobility of this species."
She said the saltwater crocodile remains one of the most widely distributed reptiles on Earth.
But before the Seychelles population was exterminated, its range was even larger — stretching more than 7,000 miles from Vanuatu in the Pacific to the Seychelles in the Indian Ocean.