Hybrid iguanas found on Little Cayman

Find ‘not good news’ for rock iguanas

A rock iguana, top, with one of the hybrid hatchlings found on Little Cayman.

The invasive green iguana species has successfully bred with the indigenous rock iguana on Little Cayman, creating a hybrid offspring scientists had thought was not possible.

According to the Cayman Islands Department of Environment, three “unusual” hatchling iguanas found on little Cayman display “intermediate characteristics” for genetic features that usually distinguish between the two species.

“Cross-breeding is the only credible interpretation,” the department noted in a press release issued Tuesday. “Now that it has occurred, perhaps for the first time, this must be considered a new and serious risk for Rock Iguanas throughout the West Indies, wherever the green iguanas have invaded.”

The reason the cross-breeding is so unusual, according to the department’s Fred Burton, is that green iguanas and rock iguanas have a different genus, or biological classification. The greens are in the genus Iguana and the rock iguanas are in the genus Cyclura. Such cross-breeding at the genus level is unusual, Mr. Burton said, although it does happen elsewhere in nature, with sea turtles being one example.

The three cross-bred iguana hatchlings are described as having the long, striped tails of green iguanas and the spotted body pattern of rock iguanas. Underneath the rock iguana’s spots, the hatchlings’ bodies appear to have a yellowish-green cast.

While the discovery is scientifically interesting, Mr. Burton said, it is not a positive development for indigenous iguana populations.

“It’s not good news at all,” he said, adding that if the greens could breed with the rock iguanas, it is at least theoretically possible they could breed with Grand Cayman’s indigenous blue iguana, which is also in the Cyclura genus.

“We haven’t seen anything yet [as far as cross-breeding with the blues], but we’re afraid it might happen,” Mr. Burton said.

A Mississippi State University laboratory is scheduling genetic tests that are expected to confirm the cross-breeding, the Department of Environment noted. Two of the three cross-bred hatchlings were caught by Mississippi State research teams who are in Little Cayman studying the rock iguanas as part of a partnership with the Department of Environment and the San Diego Zoo’s Institute for Conservation Research.

The first hybrid iguana was caught by Mike Vallee, a Cayman Islands National Trust volunteer and co-organizer of the “Green Iguana B’Gonna” program in the Sister Islands. The program seeks to control the spread of the invasive green iguanas on Little Cayman.

There may be more hybrid iguanas on Little Cayman, but no others have been found so far, the Department of Environment reported.

At this point, researchers cannot be certain if the hybrid iguanas can reproduce. They are being transferred to the San Diego Zoo to be raised and tested over the next few years.



  1. And in science we trust…”Such cross-breeding at the genus level is unusual”.
    This makes me think that nobody has a clue what really is happening in nature. GM mosquitoes- just wait and see what happens. Tampering with nature might not be such a good idea after all.


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