Distinguishing blue from green iguanas

| 05/11/2018 | 14 Comments

Is it possible for you to post an article with pictures showing the differences between a Cayman blue and the invasive green iguanas? I am hoping that when the cullers were vetted they were shown differences and how to quickly/easily spot which is which. I would love to see good photos of them side by side to see if a layman can tell the difference.


Ask Auntie, CNS Local Life, Caymanian statusAuntie’s answer: I can understand your concern, with the cull of green iguanas off to a fast start (see Cullers remove 40,000 greens in 4 days). Yes, the Department of Environment (DoE) trained the cullers who were registered on the differences between the green iguana (Iguana iguana) and blue iguana (Cyclura lewisi). And yes, there are several resources available on how to tell the difference.

The best primer to distinguish the two species is the video below:

The information and guidelines given to the cullers is posted in the the CNS Library here. The page on spotting the difference seemed at bit insufficient, but a DoE spokesperson said, “We went through the green/blue differences with every registering culler who did not already clearly know them apart. That question was raised with every single one.”

The Blue Iguana Recovery Programme website devoted a page to the blue and green differences here. It includes an excellent flyer, sponsored by CUC, though I have to say I found the all important text at the bottom a bit difficult to read. Perhaps I just need new glasses.

The DoE also sent me a PDF flyer called Rock Iguanas, which details the differences between rock and green iguanas. This is also posted in the CNS Library. The flyer is nicely descriptive, though initially I found it a bit confusing, having always been told that the rock iguanas are on the Sister Islands and the blue iguanas are on Grand Cayman

It turns out that blue iguanas are in fact rock iguanas, as are all iguanas in the West Indies. We learn something new every day. So, it’s irritatingly more cumbersome but we should probably refer to the iguanas on Cayman Brac and Little Cayman as the Sister Islands rock iguanas (Cyclura nubila caymanensis).

For those who are interested, there are no major differences between the blue iguana and the Sister Islands rock iguana except the blues are a lot prettier when they get excited. When they are, for example, hot or under restraint or fighting, they turn that classic shade of bright blue that we are familiar with. When they are cold or scared, they turn gray or black.

Sister Islands rock iguanas may get more pale if excited and darker if cold, but pretty much stay the same grey/brown colour. But the other differences from the green iguanas still applies, and since the greens are also on Cayman Brac and Little Cayman, the video and flyers are still helpful to people on those islands.

Sadly, cross breeding between the green and rock iguanas has been discovered on Little Cayman, which you can read about in this CNS article. The hybrids discovered were hatchlings and hopefully, this was a one-off because that would certainly complicate identification.

For further reading, in the DoE magazine, Flicker, edition #30, which is May/June 2017, there is an article on green iguanas on Cayman Brac. The link to that edition is here and the link to all back copies of Flicker is here.

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Category: Ask Auntie, Environmental Questions

Comments (14)

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  1. Anonymous says:

    Christian fundamentalists, could you please explain how all the blues managed to make their way from Mt Ararat when the left the ark all the way to Grand Cayman without leaving any other blues behind on the way during their journey 4,000 years ago?

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    • Anonymous says:

      In the same sense that fundamentalist Christians does not necessitate a belief in a 6000 year old earth where every species reemerges from Noah’ s ark, I imagine the same way I imagine not all God deniers necessarily believes abiogenesis without a shred of scientific evidence.

  2. Anonymous says:

    Well, if it is blue it is a blue. If it is green it is a green.

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  3. Anonymous says:

    Not sure what the issue is here. They taste very different.

  4. Anonymous says:

    Thank you for this!
    The whiners/complainers above are right in some respects about knowing the difference right away but education is key.
    I found this very helpful.

  5. Killa culla says:

    Shoot first, ask questions later.

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  6. Tom says:

    Mostly green ones are in west and south of Cayman while blue ones is in the east end where there very low count of green ones. Cullers more likely hunt in low density while east is high density of bushes.

  7. Anonymous says:

    Excuse the condescending tone, but how hard can it be to distinguish a green, striped tail from a dark blue? Unless you’re color blind then I give ya a bly.

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    • Anonymous says:

      I agree. I don’t know how anyone finds them hard to distinguish but I also don’t know how people find it hard to differentiate between car makes and models.

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