250-Year-Old Mystery Solved: These Saltwater Crocodiles Traveled Thousands of Miles Across the Indian Ocean

Genetic evidence confirms Seychelles crocodiles were saltwater crocodiles capable of long-distance ocean dispersal, with a historic range exceeding 12,000 kilometers (~7500 miles).

Historical records from expeditions over 250 years ago describe crocodiles as abundant along the shores of the Seychelles Islands. However, after permanent settlement began in 1770, the local population declined rapidly and was driven to extinction within about five decades.

A recent genetic investigation confirms that these island crocodiles belonged to the westernmost population of the saltwater crocodile (Crocodylus porosus). This finding supports an earlier theory that had relied only on physical features to link the Seychelles animals to the widespread species.

DNA Analysis of Historical and Modern Crocodile Specimens

To trace the species’ evolutionary background and geographic spread, scientists from Germany and the Seychelles compared DNA sequences from living saltwater crocodiles with mitochondrial genomes preserved in museum specimens of the genus Crocodylus.

Their analysis included material from the now vanished Seychelles crocodile population, which disappeared roughly 200 years ago.

Saltwater crocodiles are uniquely equipped for marine life compared to other crocodilian species. They possess specialized salt glands that remove excess salt from their bodies, allowing them to tolerate seawater for extended periods. This biological advantage made it possible for them to reach and establish populations on distant islands and coastlines separated by thousands of kilometers.

“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,” says reptile expert Frank Glaw of the Bavarian State Collections of Natural History (SNSB) and senior author of the study.

Ocean Dispersal and Global Range of Saltwater Crocodiles

“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,” explains first author Stefanie Agne of the University of Potsdam.

Today, the saltwater crocodile ranks among the most widely distributed reptiles on the planet. Before humans eliminated the Seychelles population, its territory extended even farther, spanning over 12,000 kilometers (~7500 miles) from Vanuatu in the Pacific Ocean to the Seychelles in the Indian Ocean.

Reference: “Mitogenomic Crocodylia phylogeny and population structure of Crocodylus porosus including the extinct Seychelles crocodile” by Stefanie Agne, Patrick Arnold, Berthilde Belle, Nicolas Straube, Michael Hofreiter and Frank Glaw, 28 January 2026, Royal Society Open Science.
DOI: 10.1098/rsos.251546

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