Two new crocodile species discovered in Caribbean – but they are already facing extinction

Scientists have identified two new species of crocodiles in the Caribbean off the Yucatán Peninsula – and both are already threatened by extinction.

The discovery, reported in a new study published in the journal Molecular Phylogenetics and Evolution, sheds further light on the true diversity of American crocodiles and underscores the need for urgent conservation efforts to protect them.

"Biodiversity is disappearing faster than we can discover what we are losing," Hans Larsson, a co-author of the study from Canada’s McGill University, said.

"Most species of crocodiles are already endangered, and rapid shoreline development threatens nearly every population.”

The Americas are home to four species of Neotropical crocodiles of the genus Crocodylus. These species live in the warm, tropical regions of the continents, inhabiting coastal, inland and insular locations.

They are a distinct group which evolved from ancestors that dispersed from Africa to the Americas around 5 million years ago.

However, much of the evolutionary history of Neotropical crocodiles remains elusive.

In the new study, researchers assessed the genetic sequences of crocodile populations from the Mexican island of Cozumel and the Banco Chinchorro atoll reef and compared these to crocodiles found across the Caribbean, Central America and on Mexico’s Pacific coast.

They found striking genetic differences in the sampled populations, leading them to conclude that the reptiles from Cozumel and Banco Chinchorro were not simply variants of the American crocodile Crocodylus acutus, but different species.

The two new species also showed physical differences between themselves. “The main differences between the populations are length and width of the skull,” the study noted.

Banco Chinchorro crocodiles were characterised by a relatively long and broad snout compared to those on Cozumel.

“Our analysis supports Banco Chinchorro and Cozumel as genetically unique isolated populations,” researchers wrote, calling the results “totally unexpected”.

"We assumed Crocodylus acutus was a single species ranging from Baja California to Venezuela and across the Caribbean. Our study is the first to extensively explore genomic and anatomical variation in these animals,” said José Avila-Cervantes, another author of the study.

The newly identified species were found to live in isolated populations of fewer than 1,000 breeding individuals, sparking concerns about their future. “Estimated effective population sizes are only in the order of five hundred individuals in each population,” the study noted.

Although their populations appeared stable, researchers warned that limited numbers and habitat restrictions left them vulnerable.

"The rapid loss of biodiversity can only be slowed if we know what species are most at risk," Dr Larsson said.

"Now that we recognise these crocodiles as distinct species, it’s crucial to protect their habitats. Limiting land development and implementing careful conservation strategies on Cozumel and Banco Chinchorro will be key to ensuring their survival.”