The Grand Cayman Blue Iguana (Cyclura lewisi) is a unique and magnificent creature, but one which stands on the brink of extinction. Fortunately, due to the National Trust for the Cayman Islands’ Blue Iguana Recovery Programme and the assistance from a variety of volunteers, it has managed to take a few steps forward over recent years.
The Blue Iguana is endemic to Grand Cayman – meaning it is found nowhere else in the world. It is related to the Rock Iguana found on Cayman Brac and Little Cayman, but is quite distinct. It gets its local name from its remarkable blue colouration which is particularly notable in adult males.
Being cold-blooded creatures, iguanas need to warm themselves in the sunshine to become active. Early in the day, when they are cool, the adult iguana is a uniform dark grey. This colour absorbs heat very efficiently. As the animal warms up, it has to ensure that it does not overheat. To achieve this, the cells responsible for this colouration (known as chromophores) contract. This reveals the distinctive powder blue colour underneath, which is paler and does not absorb heat well.
Iguanas are large lizards with red eyes and a row of spines which run from the back of the head to the tip of the tail. The male is larger than the female and has substantial jaw muscles giving it a very strong bite! They are, however, vegetarian, foraging for fruits, flowers and leaves.
Iguanas never stop growing, although the growth rate does slow down with age. Adults of five feet in length from nose to tail are not uncommon. They are not sociable creatures and tend to live alone, not encouraging others to stay in their territory. When feeling threatened, iguanas turn themselves sideways to the foe, draw themselves up as high as possible on their four legs and flatten their bodies laterally so that the area they expose to their opponent is as large as possible. Fierce fights do occur amongst males during mating season.
The behaviour of males and females leading up to the short mating season (usually the first two weeks in May) is markedly different. The female selects an area with enough food supplies to sustain her which is also suitable for her nest. This is particularly crucial as the eggs will not hatch if they get too hot, too wet or too dry. Males, on the other hand, roam widely and can cover the territories of many females, ready to mate with each as they come into season. Much of their time is spent warding off rivals, which means that the largest and strongest of the males mate most frequently. This behaviour continues into late May, until all the females cease to be receptive and the males gradually loose interest.
Six weeks after mating, the female will excavate her nest in a patch of earth and lay her eggs which are comparable in size to a chicken’s egg. Young females lay fewer eggs in a clutch than mature mothers who can produce as many as fifteen or twenty eggs at a time. The tunnel leading to the egg chamber is carefully filled in and disguised with leaves, grasses and other debris. The female then guards her nest site for a few more weeks to ensure the safety of her brood. The whole process takes a lot out of the iguana and by this time she can be quite emaciated and gaunt. She must roam more widely to feed and build up her strength again. This explains to a large extent why females are never as large as the males.
After an incubation period of about ten weeks, the baby iguanas start to hatch. At birth they are already about eight inches long, having been curled up tight inside the egg. The hatchlings wait until all their brothers and sisters are also hatched, each drawing nourishment from its egg sac, before exiting the nest using their joint strength to dig their way to the surface. Once out in the open air, they quickly scatter into the undergrowth. Each must then fend for itself. The young iguanas are very vulnerable to birds and snake (their main predators) at this stage, although they grow extremely fast.
It is a sad fact that the major problems facing Cayman’s iguanas are human related. When the first settlers arrived nearly 300 years ago, it is thought that many of these creatures lived on the coast, laying their eggs in the sand on the edge of the beach: a pattern of behaviour that can still be seen in the Little Cayman Rock Iguana. As time passed, humans, who bought with them dogs, cats and rats, preferred these areas too, and soon the iguanas were forced to retreat inland, where nesting sites were harder to find.
Yet the iguanas were able to hang on. They learned that the edge of newly cleared farmland was a suitable habitat with open areas for sunning themselves, soil for nesting, and ample bush for foraging and security. The dangers posed by roaming pets and the farmer’s gun were not quite enough to destroy the population entirely. But now things are changing again.
When initial studies were done in the 1980’s, prospects for the Grand Cayman Blue Iguana looked bleak. They had already disappeared from over 90% of the island, and a remnant of those that had survived faced seemingly insurmountable odds with rapid development, illegal trapping, feral dogs and cats and road kills. The Trust’s Blue Iguana Recovery Programme was set up in 1990 combining field research, captive breeding, public education, habitat protection and reintroduction. It is only with this continued effort that it may still be possible to save this unique creature from extinction.
Source: Cayman Islands National Trust