Scientists didn’t think it was possible but they are wrong. The invasive green iguanas have successfully bred with the indigenous rock iguana on Little Cayman producing hybrids.

In a release on Tuesday (20) the Cayman Islands Department of Environment said the strangely coloured and patterned hatchlings show intermediate characteristics for features that normally distinguish the two species and cross breeding is the only credible interpretation.

The release said, “Cross-breeding between green iguanas and rock iguanas has never been considered possible because the genetic difference between the two was thought to be too profound. 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 first of the hybrid hatchlings was caught in the wild recently by Mike Vallee, who with fellow volunteer Ed Houlcroft coordinates the “Green Iguana B’Gonna” programme for the National Trust on Little Cayman.

Another two hybrid hatchlings were caught soon afterwards by Jeanette Moss, field assistant Tanja Laaser and Dr Mark Welch, who were in Little Cayman leading the Mississippi State University research team studying the Sister Islands’ rock iguanas, in partnership with the DoE and the San Diego Zoo Institute for Conservation Research.

Local volunteers and the Mississippi research team have been searching for more hybrid hatchlings, and although so far just three have turned up, the scientists have no idea how many more may have hatched from the hybrid nest and dispersed into the surrounding vegetation.

A Mississippi State University laboratory is scheduling genetic tests that are expected to confirm the cross-breeding.

The hatchlings are small, like green iguana hatchlings, with the same long striped tails but with different-shaped heads. The body shows classic rock iguana patterns of dark chevrons and spots. Under the rock iguana patterns shines a yellow base colour tinged with green.

The hatchlings will be transferred to the San Diego Zoo Institute for Conservation Research to rear and test for fertility over the next several years.

Their presence in the Cayman Islands is a serious risk to native rock iguanas.

IMAGES:

Rock Iguana hatchling and hybrid (Photo by Jeanette Moss and Tanja Laaser)

Green iguana hatchling (top) and one of the hybrid hatchlings (below) (Photo DoE)