National Geographic Daily News
A Cuban crocodile.
A Cuban crocodile at the National Zoological Park in Washington, D.C. (file picture).

Photograph by Paul Sutherland, National Geographic

Christine Dell'Amore

National Geographic News

Published June 24, 2011

There's a new Cuban crisis—the island country's rare crocodile is being loved to death by its American cousin, a new study suggests.

Mating Cuban crocodiles and American crocodiles are creating hybrid offspring that threaten the survival of the Cuban species, which has dwindled to about 4,000 wild animals in two isolated Cuban swamps. The ten-foot-long (three-meter-long) reptile is listed as critically endangered by the International Union for Conservation of Nature (IUCN).

"That means any loss of animals—be it loss in fact or loss through hybridization—is a grave concern," said John G. Robinson, executive vice president for conservation and science at the Wildlife Conservation Society.

American crocodiles, which are found throughout the Caribbean, are not considered threatened by IUCN. The animals have increasingly moved into the Cuban crocodile's remaining freshwater habitat as it becomes more brackish—or salty—due to agricultural activities, said Robinson, who was not involved in the research.

The Cuban crocodile is the most terrestrial of the crocodiles—walking instead of waddling on their bellies like other croc species, he added. "They're very cool beasts."

(Read more about Cuban crocodiles on the Nat Geo Wild TV channel's website.)

Surprising Croc-Hybrid Discovery

For the study, scientists led by Yoamel Milián-García, of the University of Havana, took DNA samples from 89 wild-caught crocodiles and 2 captive crocodiles.

Surprisingly, the results showed that American crocodiles living in Cuba are more closely related to Cuban crocodiles than to other American crocodile populations in Central America.

This suggests that the American and Cuban species are mating much more than thought. When different species mate to create hybrids, genes mix, and eventually one lineage can cause the extinction of the other.

(See "Interspecies Sex: Evolution's Hidden Secret?")

The scientists haven't done behavioral studies to find out if the hybrids are stronger or more aggressive, which can sometimes happen when species interbreed.

Yet the study "will be a wake-up call" for conservationists in Cuba, who have already put a lot of effort into protecting the Zapata swamp—home to about 3,000 of the Cuban crocodiles, WCS's Robinson said.

One obvious strategy, he said, would be to restore the flow of fresh water into the swamps, which would make the habitat less palatable for the American crocodile.

Cuban-American hybrid crocodile research published in the spring issue of the Journal of Experimental Zoology.

0 comments

Share

How to Feed Our Growing Planet

  • Feed the World

    Feed the World

    National Geographic explores how we can feed the growing population without overwhelming the planet in our food series.

See blogs, stories, photos, and news »

The Innovators Project

See more innovators »

Latest News Video

  • Mazes: Key to Brain Development?

    Mazes: Key to Brain Development?

    Mazes are a powerful tool for neuroscientists trying to figure out the brain and help us learn to grapple with the unexpected.

See more videos »

See Us on Google Glass

Shop Our Space Collection

  • Be the First to Own <i>Cosmos: A Spacetime Odyssey</i>

    Be the First to Own Cosmos: A Spacetime Odyssey

    The updated companion book to Carl Sagan's Cosmos, featuring a new forward by Neil deGrasse Tyson is now available. Proceeds support our mission programs, which protect species, habitats, and cultures.

Shop Now »