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 Common 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.
Common Iguanas are now numerous and sighted often, while the critically
endangered Blues are almost never seen outside protected areas. More and
more, people are beginning to mistakenly assume the Common Iguana
actually IS the Cayman's own Blue Iguana!
The two species are very different, and cannot 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 these pictures, and note these
characteristics:
- Common
Iguanas have 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.
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Juvenile Green |
Juvenile Blue |
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Adult Green |
Adult Blue |
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 most ancient Rock Iguana is Cyclura pinguis, which survives
on Anegada. Like the Blue Iguana, it is now critically endangered. It
was the ancestor to this iguana which dispersed first from the Puerto
Rico bank to Hispaniola, then onwards to the north and western islands,
and has since diversified on different islands into 9 species and
several additional subspecies.
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,
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.
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