Common Iguanas thrive on GC

Know your islands

Common Iguanas now abundant on Grand Cayman, particularly in West Bay, have led the community to believe there are many Blue iguanas roaming the island.

Blue iguana

Blue iguana

With this frequent case of mistaken identity maybe we should revisit the differences between our endangered Blue Iguana, which is almost never seen outside protected areas, and the frequently sighted Green Iguana.

Iguanas (Iguana iguana), also known as Green Iguanas, have escaped from the domestic pet trade on Grand Cayman, and are breeding in the wild throughout the western districts of the island. They are native to Central and South America, where they evolved in the presence of many predators.

Common Iguanas therefore have instinctive strategies to avoid being eaten by cats and dogs, and they are thriving in suburban areas where Blue Iguanas would not stand a chance.

The two species are very different, and can not breed together. They don’t even speak the same language – when a Blue Iguana threatens a Common Iguana by head-bobbing, the Common Iguana does not understand. Size for size, the Blue Iguana is much stronger and much more aggressive.

To tell them apart, look at the pictures, and note these characteristics:

Common Iguana has spines on the dewlap (the skin flap under the chin). The Blues never have spines here.

Common Iguanas have a very long, whip-like tail, with vivid black bands. Blues have a thicker tail, without obvious bands.

Common Iguanas have a large circular scale, like a shield, on the cheek beneath the ear. Blues have their cheeks covered with cone-shaped, pointed scales when they are old, and never have a large circular one.

Blue Iguana’s relatives:

The Blue Iguana is one of the West Indian Rock Iguanas, which are all classified in the genus Cyclura. Uniquely different species of Cyclura are found from the Virgin Islands through the Greater Antilles to the Bahamas.

The Blue Iguana evolved more recently from ancestors of its nearest relative, the Cuban Iguana (Cyclura nubila).

Cuban Iguana ancestors also made the crossing to Little Cayman and Cayman Brac, where they evolved into a unique subspecies, Cyclura nubila caymanensis, and to the southern Bahamas where they evolved into a new species, Cyclura cychlura.

The Blue Iguana was long thought to be another subspecies of the Cuban Iguana, and but recent genetic evidence has led to a revision, and the Blue Iguana is now considered a unique species, Cyclura lewisi.

If Cyclura lewisi and Cyclura nubila caymanensis are artificially brought into contact, they can still breed and produce fertile offspring. Naturally, they have always been separated by at least 67 miles of open ocean.

Protect Cayman’s Wildlife! For more information or if you would like to contribute to the Blue Iguana Recovery Program, please visit www.blueiguana.ky or call the National Trust for the Cayman Islands at 949-0121. Photographs generously provided by Lois Blumenthal, Courtney Platt, John Binns, and Mark Orr.

Last week’s answer: The name of the only duck to breed in the Cayman Islands is the West Indian Whistling Duck.

Trivia question: What is the name of the native tree that can be easily mistaken for Mahogany at a distance?

Look for the answer in next week’s feature!

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