Somewhere around 1770, French colonists arrived on the Seychelles and found crocodiles waiting on the beaches. Within a few decades, every last one was dead. The skins and skulls ended up in European museum drawers, labeled and largely forgotten. Now, more than two centuries later, geneticists have pulled DNA from those specimens and matched it to saltwater crocodiles living in Borneo and New Guinea, roughly 3,000 kilometers away across the open Indian Ocean. The finding, published in May 2026 in Royal Society Open Science, settles a question that has nagged herpetologists since the archipelago’s crocs vanished: were they a unique island species, or the far-flung outpost of the world’s largest living reptile?
The answer is the latter, and it rewrites what scientists thought was possible for crocodilian dispersal.
Museum skins, modern sequencing
The research team, led by scientists including herpetologist Frank Glaw of the Bavarian State Collection of Zoology and researcher Stefanie Agne, extracted mitochondrial DNA from preserved 19th-century crocodile specimens held in European natural history collections. They then sequenced full mitochondrial genomes and compared them against a broad phylogenetic dataset spanning living Crocodylus porosus populations across the Indo-Pacific.
The result was unambiguous. The Seychelles crocodiles fell squarely within the C. porosus lineage, not in a separate endemic clade. Their closest genetic relatives were populations in Borneo and New Guinea. Glaw has described the evidence as demonstrating long-distance oceanic dispersal at a magnitude previously considered unlikely for any crocodilian species.
That genetic match carries a staggering geographic implication. The Seychelles sit in the western Indian Ocean, about 1,500 km east of mainland Africa and thousands of kilometers from any known saltwater crocodile breeding range. For crocodiles to have colonized the islands naturally, they would have had to cross at least 3,000 km of open water. Saltwater crocodiles are powerful swimmers, and satellite-tracking research, notably work by Hamish Campbell and colleagues published in the Journal of Animal Ecology, has documented individuals riding ocean currents for hundreds of kilometers. But a transoceanic crossing of this scale had never been genetically demonstrated until now.
Fifty years from arrival to extinction
The Seychelles were uninhabited when France established a permanent settlement in 1770. Colonial accounts record crocodiles on the islands at that time. By the 1820s, the animals were gone. Hunting pressure and habitat disruption on small, low-lying islands left no viable breeding population. The entire arc from first European contact to local extinction took roughly 50 years.
That estimate draws on published syntheses of colonial records rather than on primary archival ledgers or hunting logs from the period. No direct examination of 1770-to-1820 Seychelles settlement documents has been cited in the study’s available materials, so the actual pace of killing could have been faster or slower than the round figure suggests. It is also possible that small, hidden populations persisted somewhat longer. Future archival work in French colonial repositories could sharpen the timeline.
What is certain is that by the early 19th century, the only physical proof that crocodiles had ever lived on the Seychelles was a handful of preserved skins and skulls scattered across European collections. Those specimens sat in storage for generations before modern sequencing technology made it possible to read their DNA.
Open questions and wider implications
Several pieces of the puzzle remain unresolved. The study’s supplementary data, including museum catalog numbers, tissue sampling locations, and sequence alignments, have been deposited in a curated Figshare repository. Those files have not yet been independently cross-checked against physical specimen labels by outside researchers. Until that verification occurs, the provenance chain linking specific skins to specific Seychelles collection events rests on the authors’ documentation.
A broader biological question also hangs open. If ocean-current dispersal explains how saltwater crocodiles reached the Seychelles, similar colonization events could have occurred on other remote Indian Ocean island groups: the Chagos Archipelago, the Maldives, the Andaman Islands. Targeted mitogenomic sampling of crocodile remains or environmental DNA from those locations could reveal additional C. porosus haplotypes clustering with the same Southeast Asian source populations. No such sampling program has been announced, and the current study does not extend its genetic analysis beyond the Seychelles specimens.
There is also an important distinction between demonstrating a minimum dispersal distance and reconstructing the exact route. The genetic match shows that the Seychelles animals ultimately derived from Southeast Asian stock, and the oceanographic setting makes a roughly 3,000 km journey the simplest explanation. But the data cannot tell us whether colonization happened through a single extraordinary voyage, multiple successive crossings over generations, or occasional stops on now-submerged banks and reefs. The study rules in long-distance oceanic dispersal without pinning down every step.
Notably, no saltwater crocodiles are known to inhabit the western Indian Ocean today. The nearest living populations are in coastal Southeast Asia, northern Australia, and parts of eastern India and Bangladesh. Nile crocodiles (Crocodylus niloticus) live on nearby Madagascar, but they belong to a different species entirely and were not part of this analysis. Whether C. porosus could naturally recolonize the Seychelles under current ocean conditions is unknown, though the islands’ small size and dense human settlement would make long-term survival unlikely even if a stray individual arrived.
What old bones can still teach
Despite the uncertainties, the central conclusion is robust: the extinct Seychelles crocodiles were not a distinct island species but part of a widespread Indo-Pacific predator that managed to reach one of the ocean’s most isolated archipelagos. That realization reframes the Seychelles extinction not as the loss of a unique lineage, but as the local erasure of a remarkable dispersal success story.
For conservation planners, the work suggests that rare, long-distance colonization events by marine and coastal species may only become visible when genetics and historical collections are combined. For museum curators and field biologists, it is a reminder that specimens collected two centuries ago, long divorced from their original ecosystems, can still yield discoveries. Skins and skulls that sat in drawers through two world wars have now illuminated how a top predator once threaded its way across the Indian Ocean, and how quickly human expansion erased it from the map.
More from Morning Overview
*This article was researched with the help of AI, with human editors creating the final content.
