Scientists discover 2 new species of crocodile hiding in plain sight

Researchers have identified two new crocodile species living on isolated islands in the Caribbean — and they're both threatened with extinction, a new study has found.

The reptiles, previously thought to be American crocodiles (Crocodylus acutus), separately inhabit the island of Cozumel and the atoll of Banco Chinchorro off Mexico's Yucatán Peninsula. Both populations have around 500 individuals.

Scientists identified the as-of-yet unnamed species while studying the genetics of crocodiles across Mexico's Pacific coast, Central America and the Caribbean. The team found stark genetic differences between the Cozumel and Banco Chinchorro populations and the rest of the American crocodile species, concluding that the island crocodiles were separate species, according to a statement released by McGill University in Canada.

"These results were totally unexpected," study lead author José Avila-Cervantes, who carried out the genetics research during his graduate studies at McGill University, said in the statement. "We assumed Crocodylus acutus was a single species ranging from Baja California to Venezuela and across the Caribbean."

The researchers' findings will appear in the upcoming June volume of the journal Molecular Phylogenetics and Evolution — they were first published online on March 28.

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American crocodiles live across 18 countries, ranging from the southern tip of Florida to the Caribbean and northern South America. They share some of that range with Cuban crocodiles (C. rhombifer) in Cuba and Morelet's crocodiles (C. moreletii) in Mexico, Guatemala and Belize.

The researchers were studying variation across all three species when they identified the two new species on Cozumel and Banco Chinchorro. Their work involved capturing and releasing crocodiles to extract blood and tissue samples for DNA analysis. The team also used genetic data from previous studies and compared physical differences between the crocodiles, according to the study.

The main physical difference between the different species is that their skulls vary in length and shape. For example, the Banco Chinchorro crocodiles have a longer and broader snout compared to those of Cozumel Island, according to the study.

The discovery of two new species could be important from a conservation perspective. Crocodiles in the region are already under threat from human activities including urbanization, pollution and tourism. The researchers found the populations on Cozumel and Banco Chinchorro appear to be stable, but that they are vulnerable due to their small size and restricted habitat, according to the statement.

"Now that we recognize these crocodiles as distinct species, it’s crucial to protect their habitats," Hans Larsson, a biology professor at McGill University and the study's principal investigator, said in the statement. "Limiting land development and implementing careful conservation strategies on Cozumel and Banco Chinchorro will be key to ensuring their survival."

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