Genetic Study Solves Mystery of Crocodiles Once Seen on Seychelles Beaches

For a long time, these Seychelles crocodiles looked like a sailor’s legend. Yet they were very real. A genetic study has just revealed their identity and their improbable journey: thousands of kilometers across the Indian Ocean, before a rapid disappearance caused by human arrival.

Ancient testimonies confirm the presence of crocodiles in the Seychelles

In the 16th century, the first European travelers described an almost unreal scene: crocodiles settled near the Seychelles’ beaches, in the mangroves, at river mouths. For a long time, these testimonies drifted between natural history and adventure narrative, as if the archipelago had kept a secret too large for its postcards.

Then came the colonists, from 1770 onward. In a few decades, the animal vanished from the landscape. Hunting, destruction of habitats, conflicts with humans: the great reptile could not withstand it. About fifty years were enough to erase an entire population, leaving behind only bones, old notes and a stubborn enigma.

Museum DNA Reveals the Real Identity of the Seychelles Crocodiles

The case wasn’t revived on a beach, but in museum collections. German and Seychellois researchers analyzed rare historical specimens, including fragments kept at the Seychelles National Museum, to compare their DNA with that of modern Crocodylus crocodiles. The study was published in Royal Society Open Science.

The surprise was considerable: these animals were not an unknown species, nor a Nile crocodile misplaced in colonial imagination. They belonged to Crocodylus porosus, the saltwater crocodile, regarded as the largest living reptile. A creature capable of exceeding six meters in some cases, but above all a quiet champion of oceanic dispersion.

The key tool here is the mitochondrial genome, a part of DNA especially useful for tracing kinship. Genetic profiles showed that the Seychellois crocodiles were related to populations located far away in the Indo-Pacific. In other words, the puzzle did not tell of a local anomaly, but of a story of connection across an ocean.

The Saltwater Crocodile Conquered the Seychelles After an Extraordinary Crossing

The figure is almost dizzying: the ancestors of these crocodiles would have traveled at least 3,000 kilometers to reach the Seychelles. Not necessarily in a single heroic crossing, like a sea monster launched into a solitary epic. Researchers rather point to gradual movements, driven by currents, across several generations.

The saltwater crocodile indeed has the biological toolkit for such an feat. Thanks to salt glands, it tolerates seawater far better than most reptiles. It can skirt the coastlines, cross oceanic arms, wait for favorable conditions. It is not a fish, but it knows how to use the sea as a route.

This discovery also broadens our view of its ancient range. Before the extinction of the Seychellois population, the saltwater crocodile’s range may have stretched over more than 12,000 kilometers, from Vanuatu in the Pacific to the Seychelles in the Indian Ocean. A vast map, long underestimated, where the islands serve as living waypoints.

Their Rapid Extinction Highlights the Fragility of Island Ecosystems

The tale strikes because it unfolds in two opposing movements. On one side, a species capable of crossing the ocean and colonizing a remote archipelago. On the other, a population unable to survive more than a few decades under sustained human settlement. Nature can deliver extraordinary feats, then lose the game under brutal pressure.

This study also underscores the importance of natural history collections. Incomplete skulls, fragments, forgotten samples can still answer questions that are centuries old. Museums do not merely preserve the past: they sometimes hold the keys to a biodiversity that vanished before it was fully understood.

One lingering question remains. How many other animal presences, deemed anecdotal or legendary in ancient accounts, still await their genetic verification? In the Seychelles, the crocodiles will probably not return to haunt the lagoons. But their DNA reminds us that the oceans were long bridges, not merely borders.