Know Your Islands Protecting the Rock Iguana

The Little Cayman Rock Iguana (Cyclura nubila caymanensis) is to be found solely on Cayman Brac and Little Cayman. It is a subspecies of the Cuban Rock Iguana. 

This large lizard, grey-brown with black markings, has 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 chosen area.  

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, especially during mating season among males who are aggressive from a very early age. 

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. 

Six weeks after mating, the female will excavate her nest in a patch of earth and lay her eggs which are about the size of a hen’s egg. Young females lay fewer eggs in a clutch than mature mothers who can produce as many as 15 or 20 eggs at a time. The tunnel leading to the egg chamber is carefully filled in and disguised with leaves, grasses and other debris. After an incubation period of about 10 weeks, the baby iguanas start to hatch. At birth they are already about eight inches long, having been curled up tight inside the egg.  

It is a sad fact that the major problems facing Cayman’s iguanas are human-related. When the first settlers arrived on Cayman Brac about 200 years ago, they brought their domestic dogs with them. The dogs soon learned that killing iguanas was an exciting way to get an extra meal. A once abundant iguana population has now been reduced to a few tens of survivors. Now another domestic animal threatens to be the death knell for the iguana population on Cayman Brac: feral cats are now found in huge numbers, and they eagerly pursue juvenile iguanas. 

The same pattern of development that has almost destroyed the iguanas elsewhere can be seen beginning on Little Cayman and Cayman Brac, too, and at a much faster rate. Coastal nesting habitat is being taken over by housing development, feral cats are becoming established, and the first dogs are now resident on the island. Increasing traffic on the roads is killing several adult iguanas every year. If preventative measures are not taken soon, it is inevitable that Little Cayman’s now abundant iguanas will follow Grand Cayman’s Blue Iguana to the brink of extinction. 

 

This weekly column was submitted by the National Trust for the Cayman Islands. The National Trust can be contacted at 749-1121 or via email at info@nationaltrust.org.ky 

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