Three unusual hatchling iguanas from Little Cayman have just been examined by the Cayman Islands Department of Environment and found to be hybrids. They are apparently the offspring of an invading Green Iguana female which mated with a native Sister Isles Rock Iguana.

Genetics work is now being scheduled by Dr. Mark Welch, in his laboratory at Mississippi State University. This is expected to confirm the unexpected discovery. The strangely coloured and patterned hatchlings show intermediate characteristics for features that normally distinguish the two species. Cross breeding is the only credible interpretation.

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 recently caught in the wild by Mike Vallee, who with fellow volunteer Ed Houlcroft coordinates "Green Iguana B'Gonna", which is a programme of the National Trust for the Cayman Islands on Little Cayman.

Another two hybrid hatchlings were caught soon afterwards by Jeanette Moss, field assistant Tanja Laaser, and Dr. Mark Welch. Moss has been in Little Cayman leading the Mississippi State University research team studying the Sister Isles Rock Iguanas, in partnership with the Cayman Islands Department of Environment and the San Diego Zoo Institute for Conservation Research.

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.

It cannot be determined at this early age whether the hybrids will be fertile, or even if they will develop normally. Since their presence in the Cayman Islands is a serious risk to native Rock Iguanas, 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.

In searching for more of these hatchlings, the local volunteers were joined by the Mississippi research team. No more hybrid hatchlings have yet been found. It is unknown how many more may have hatched from the hybrid nest, and dispersed into the surrounding vegetation.

Residents and visitors in Little Cayman are asked to keep an eye out, and contact Ed Houlcroft or Mike Vallee in person or on 929-5655 or 924-4991 respectively, or at greeniguanabgonna@gmail.comif anyone spots a bright yellow-green, striped, and unusually small iguana hatchling with a long, thin, banded tail.

Green Iguana hatchling (top) and one of the hybrid hatchlings (below). Photo by DoE.

Sister Isles Rock Iguana hatchling (top) and one of the hybrid hatchlings (below). Photo by Jeanette Moss / Tanja Laaser

For more information contact:

Department of Environment – Fred Burton, Manager / Terrestrial Resources Unit

E-mail: Direct: 743-5915; Cell: 916-2418

Green Iguana B'Gonna – Ed Houlcroft, project coordinator

E-mail: Tel: 929-5655

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