Researchers Discover Two Crocodile Species

McGill University researchers, in collaboration with Mexican scientists, have discovered two previously unknown species of crocodiles, one living on the island of Cozumel and the other on the atoll of Banco Chinchorro, both off the Yucatán Peninsula. The findings challenge long-held assumptions about the American crocodile (Crocodylus acutus) and highlight the urgent need for conservation efforts, the researchers say.

"Biodiversity is disappearing faster than we can discover what we’re losing," said Biology Professor Hans Larsson, the principal investigator. "Most species of crocodiles are already endangered, and rapid shoreline development threatens nearly every population. Our research aimed to uncover the true diversity of crocodiles on these isolated islands."

Larsson and his team analyzed the genetic sequences of crocodile populations from Cozumel and Banco Chinchorro. Comparing these sequences to those of crocodiles across the Caribbean, Central America and Mexico’s Pacific coast, they found striking levels of genetic differentiation, leading the researchers to conclude that these populations were not simply variants of Crocodylus acutus. The two new species have not yet been named.

"These results were totally unexpected," former Larsson graduate student and lead author José Avila-Cervantes said. "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."

This discovery has significant conservation implications, the researchers said. The newly identified species live in small, isolated populations, each numbering fewer than 1,000 breeding individuals. While both populations appear stable, their limited numbers and habitat restrictions make them vulnerable.

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

The research was conducted with the help of local colleagues, including Pierre Charruau at El Colegio de la Frontera Sur in Mexico. The team captured and released crocodiles, collecting blood and scale samples for analysis. Genetic sequencing was carried out at McGill by José Avila-Cervantes during his graduate studies, with additional research on skull morphology by fellow McGill graduate student Hoai-Nam Bui.

Reference: Avila-Cervantes J, Charruau P, Cedeño-Vázquez JR, et al. Novel island species elucidate a species complex of Neotropical crocodiles. Mol Phylo Evo. 2025. doi:10.1016/j.ympev.2025.108341

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