Department of Environment conducts genetic testing of green iguanas

Tests prompted by 2016 birth of hybrid iguanas

The Department of Environment is compiling a library of green iguana genetics to determine whether the first documented case of hybridization with the rock iguana on the Sister Islands was a fluke or a pattern.

The hybridization case – which occurred in August 2016 – was recently documented in the scholarly journal Biological Invasions. An invasive female green iguana gave birth to a clutch of offspring that appeared to be hybridized, and the DoE and researchers from Mississippi State University conducted genetic testing that appeared to confirm that the two species were able to cross-breed.

The DoE is following up by collecting green iguana genetics to establish a baseline, and it recently captured a female of reproductive age in the same range where the hybridization occurred. Further testing may determine whether it was an isolated incident or a harbinger of things to come.

“We’re certain that was one clutch. We obviously don’t know what else is out there,” said Jane Haakonsson, terrestrial unit research officer for the DoE. “We’re trying to determine whether the hybridization was 15 or 20 independent colonization events or just one female.”

There were three hatchlings found from the hybrid clutch, and the researchers found another three iguanas that appeared to be from the same clutch in the following year. The genetic testing has not yet determined whether the hybrid iguanas will be able to reproduce on their own.

The recently captured female green iguana was found with 41 eggs, which are undergoing genetic testing at a laboratory connected to Mississippi State researchers. With the information found through testing, the DoE can set priorities for control and eradication policies on Little Cayman and Cayman Brac.

Ms. Haakonsson said there is no reason to believe that the green iguana and blue iguana can produce hybrids, but then again, she said that hybridization had never been documented previously.

“At this point in time, nobody had expected to see hybridization,” she said. “And we’re seeing it.”

A side-by-side comparison of the hybrid and green iguana hatchlings.

The testing occurs at the same time that Cayman is registering applicants for a nationwide cull of the green iguana. The DoE is hoping to cull one million green iguanas in one year, and it’s requiring that applicants will commit to killing at least 400 a month. Each applicant who meets that standard will be paid between $4.50 and $5 per iguana, with the first year of the cull expected to cost $7 million.

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