The preferred habitat for the blue iguana is rocky, sunlit, open areas in dry forests or near the shore, as the females must dig holes in the sand to lay eggs in June and July.

The species' decline is mainly being driven by predation by cats and dogs, and indirectly by reduction in suitable habitat as fruit farms are converted to pasture for cattle grazing.

Since 2004, hundreds of captive-bred animals have been released into a preserve on Grand Cayman run by a partnership headed by the Durrell Wildlife Conservation Trust, in an attempt to save the species.

The specific name, lewisi, commemorates the surname of the scientist who collected the holotype of this species, Charles Bernard Lewis.

Lewis obtained two blue iguanas, a male and a female, which were later lodged with the Natural History Museum, London.

[7] Chapman Grant, in an article published in 1940, formally described the blue iguana as a separate taxon for the first time, classifying it as the trinomial C. macleayi lewisi.

[2][3] Burton, who runs the captive breeding program on the island, reclassified the blue iguana as a distinct species in 2004.

Grant reported seeing caymanensis on Grand Cayman in 1940, but Burton states that this was likely a mistaken sighting made during rainy weather.

Although none of this might be used to traditionally delineate a population as a species, he proposed using the "general lineage concept" introduced by Kevin de Queiroz in 1998 to do so anyway.

[13] An example of island gigantism, the blue iguana is the largest native land animal on Grand Cayman with a total nose-to-tail length of 5 ft (1.5 m) and weighing as much as 30 lb (14 kg).

[16] When they first emerge from the nest, the neonates have an intricate pattern of eight dark dorsal chevrons from the crest of their necks to their pelvic area.

These markings fade by the time the animal is one year old, changing to mottled gray and cream and eventually giving way to blue as adults.

Comparison with other Cyclura species in the region strongly suggests that there was once a coastal population of blue iguanas which was gradually displaced or extirpated by human settlements and the construction of roads.

[20] Blue iguanas released into the Queen Elizabeth II Botanic Park on Grand Cayman were radiotracked in 2004 to determine the home range for each animal.

[16] A clutch of 1 to 21 eggs is usually laid in June or July depending on the size and age of the female, in nests excavated in pockets of earth exposed to the sun.

[27] Restored free-roaming subpopulations in the Queen Elizabeth II Botanic Park and the Salina Reserve numbered approximately 125 individuals in total after an initial release in December 2005.

[28][29] In April 2007, after another large-scale release, there were 299 blue iguanas living in the wild, with hundreds more being raised in captivity on Grand Cayman.

Land clearance within remnant habitat is occurring for agriculture, road construction, and real estate development and speculation.

[28] The conversion of traditional crop lands to cattle pasture is eliminating secondary blue iguana habitat.

[33][34] In 2008, six blue iguanas were found dead in the preserve within Queen Elizabeth II Botanic Park on Grand Cayman.

The iguanas were apparently killed by human vandals armed with knives and two of the slaughtered animals were gravid females about to lay eggs.

[27] Each released blue iguana wears a string of colored beads through its nuchal crest for visual identification at a distance, backed up by an implanted microchip and a high-resolution photograph of its head scales.

[14] The Blue Iguana Recovery Programme grew from a small project started in 1990 within the National Trust for the Cayman Islands.

[28] This program operates under a special exemption from provisions in the Animals Law of the Cayman Islands, which normally would make it illegal for anyone to kill, capture, or keep iguanas.

[22][38] A rapid numerical increase from a maximum possible number of founding stock is sought to minimize loss of genetic diversity caused by a population bottleneck.

[22] Restored sub-populations are present in two non-contiguous areas —the Salina Reserve and the Queen Elizabeth II Botanic Park.

[15] Habitat protection is still vital,[15][22][28] as the Salina Reserve has only 88 acres (360,000 m2) of dry shrubland, which is not enough to sustain the 1,000 blue iguanas that were planned to be restored to the wild.

When the wild sub-populations have reached the carrying capacity of their respective protected areas, release of head-started animals will be phased out.