Cayman Islands ground iguana (Cyclura nubila)
|Also known as:||Cuban ground iguana, Cuban iguana|
|French:||Cyclure des îles Cayman, Iguane terrestre des îles Cayman|
|Size||Average male length (excluding tail): 405 – 544 mm|
Average female length (excluding tail): 320 – 440 mm (2)
Classified as Vulnerable (VU A1cde+2ce) on the IUCN Red List 2004 (1) and listed on Appendix I of CITES (3). Subspecies: Lesser Caymans iguana (C. n. caymanensis) is classified as Critically Endangered (CR B1+2abcde) and the Cuban ground iguana or Cuban iguana (C. n. nubila) is classified as Vulnerable (VU A1acde+2ce) on the IUCN Red List 2004 (1).
The Cayman Islands ground iguana is a large iguana with a conspicuously high crest of scales running down the length of its back (4). The nominate subspecies, the Cuban ground iguana (C. n. nubila), has an overall grey to greenish body colour that is stippled with yellow or tan, and the head and tail are tan coloured. The Lesser Caymans iguana (C. n. caymanensis) varies in colour, but adult males are typically light grey with a tan-coloured head, tail, limbs and strip running down the centre of the back. A pale blue or reddish-pink hue can frequently be seen on the dorsal crest and head, and the chest and belly are sometimes a rusty, burnt-orange colour. Partial black bars ring the body and tail, although usually fade with age. Females are significantly smaller than males and less brightly coloured, lacking any blue or red colouration on the head, and often feature a green tinge to their entire body. Juveniles of both subspecies are patterned with a series of five to ten pale chevrons on their back, extending down their sides, bordered by black (4).
The Cuban ground iguana (C. n. nubila) is relatively widely distributed around Cuba and its many surrounding islets, and a population was also introduced on Isla Magueyes, southwest of Puerto Rico, in the mid-1960s (1) (5). The Lesser Caymans iguana (C. n. caymanensis) is native to only two small islands, Cayman Brac and Little Cayman, but fewer than 50 individuals are currently thought to remain on Cayman Brac (1).
All rock iguanas (Cyclura) require habitat with suitable forage plants, basking areas, retreats and nesting sites. On Little Cayman, densest populations occur in dry evergreen bushlands and thickets growing on exposed and highly weathered rock. However, the only available nesting ground here is restricted to shallow patches of soil, so many females move to coastal areas with deep sandy soils to nest (4). In Cuba, these iguanas largely occupy dry coastal areas (6), primarily near rocky limestone regions where natural retreats and suitable nesting sites are available. Here, foraging has largely been observed in concentrations of coastal mangroves (4).
The Cayman Islands ground iguana has a generalist diet, feeding on the leaves, fruit and flowers of a wide variety of plants. When available, animal matter such as land crabs will also be scavenged, or slow-moving insects will be preyed upon. Certain seasonal changes in the diet are evident, particularly in the exploitation of fruits that are more widely available with the rainy season (4).
The reproductive behaviour of this iguana is similar to that of other rock iguanas (Cyclura), with males displaying strong territorialism, aggressively defending access to females within their territory. The smallest, youngest males do not hold territories and during the breeding season move from one territory to another attempting to court females and avoid detection by resident males (4). Courtship and mating have been recorded in April and early May for the Lesser Caymans iguana subspecies. Mating is polygynous (4) and males display to females using a series of ‘head-bobs’ to attract them (5). After sexual maturity is attained at two to three years, females will produce a single clutch of 7 to 30 eggs each year, laid into a nest dug in the sand. For the Lesser Caymans iguana subspecies, this occurs between late May and mid-June, coinciding with the onset of the rainy season (4). Females only appear to demonstrate territorial behaviour while nesting (4).
The main threats facing the Cayman Islands ground iguana across its range are habitat change and destruction and human disturbance (1). These threats are largely the result of coastal areas with sandy beaches being progressively developed for tourist resorts (6), including a number of formerly uninhabited offshore Cuban islets with populations of the Cuban ground iguana subspecies, which had previously remained relatively safe from human disturbance (4). For the Lesser Caymans iguana subspecies, the site of a proposed new, paved airstrip to replace the existing grass airstrip on Little Cayman overlaps areas of prime habitat, and the airstrip is likely to significantly increase tourism and associated development of the island. Because inland nesting sites are limited on Little Cayman, the ongoing destruction and disturbance of coastal nesting areas is of considerable concern. The Lesser Caymans iguana has also suffered from habitat destruction and mortality from road construction, commercial and residential real estate development, disturbance of sensitive nesting areas, and livestock grazing (on Cayman Brac) and farming practices. Sadly, the construction of a municipal power generating station on Little Cayman in the early 1990s has rapidly increased road construction and real estate development, and the human population, although still small, has increased seven fold.
Predation by feral cats and domestic dogs has also had a negative impact on both subspecies, in addition to egg predation by pigs on Cuba and possible predation by introduced rats on the Lesser Caymans iguana (1).
Fortunately for the Cuban ground iguana subspecies, all but one of the major iguana concentrations are either partially or fully protected (1). The Centro Nacional de Areas Protegidas is also carrying out projects directed at the conservation and reproduction of Cuban iguanas at selected localities within the National System of Protected Areas. Although no captive-breeding programme currently exists within Cuba, this is one of the future aims of the Centro Nacional de Areas Protegidas. A fairly large captive population exists in the U.S., but a break from breeding has been recommended to concentrate on more critically endangered species (4). All iguanas within the Cayman Islands, including the Lesser Caymans iguana, are protected by the Animals Law of 1976, but there is no protection of native habitats. The only protected areas currently on Cayman Brac and Little Cayman are the Cayman Brac Parrot Preserve and the Little Cayman Ramsar Site, which contain potentially important iguana habitat. No captive breeding programme exists for this subspecies, but would certainly be hugely beneficial, as would the official protection of important Cayman Islands habitat, and the eradication of feral cats across the Cayman Islands ground Iguana’s range (1). While the Cuban ground iguana subspecies is still relatively safe across a large number of protected, uninhabited, offshore islets, the Lesser Caymans iguana is dangerously close to extinction. Unfortunately, the pattern of increasing human development and disturbance in this subspecies’ range appears set to continue (4).
For more information on the Cayman Islands ground iguana see:
Alberts, A. (1999) West Indian Iguanas: Status Survey and Conservation Action Plan. IUCN/SSC West Indian Iguana Specialist Group, Gland, Switzerland and Cambridge. Available at:
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- Dorsal: relating to the back or top side of an animal.
- Nominate subspecies: the subspecies indicated by the repetition of the specific name. Thus, in this case the Cyclura nubila nubila is the nominate subspecies of the Cayman Islands ground iguana, Cyclura nubila.
- Polygyny: in animals, a pattern of mating in which a male has more than one female partner.
IUCN Red List (December, 2009)