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:''For the 1980s comedy film, see The Blue Iguana
The 'Blue iguana' or 'Grand Cayman Iguana' ('''Cyclura lewisi''') is a critically endangered species of lizard of the genus cyclura that lives on the island of Grand Cayman. Previously listed as ''Cyclura nubila lewisi'' as a subspecies of Cuban Iguana, it has been reclassified as it's own species due to genetic differences discovered in 2000. By the year 2003 less than 25 of these animals still lived in the wild and this wild population was expected to be extinct within the first decade of the twenty-first century. The animals' demise was mainly driven by feral human pets (cats and dogs) and indirectly by the destruction of their natural habitat as fruit farms were converted to land for cattle grazing.
Since 2004, 219 captive-bred iguanas 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 this critically endangered species. Some success with naturally-laid eggs has been reported.

Contents

Taxonomy

Anatomy and morphology

Habitat

Diet

Mating

Conservation

Endangered Status

Causes of Decline

Recovery Efforts

References

External links

Taxonomy

The Grand Cayman Blue Iguana, ''Cyclura lewisi'', is endemic to the island of Grand Cayman. Its closest relatives are ''Cyclura nubila nubila'' on Cuba, and ''Cyclura cychlura'' in the Bahamas, all three having apparently diverged from a common ancestor some 3 million years ago. The species has a low genetic diversity, but does not seem to suffer the same lack of vitality that afflicts other such species of rock iguana. One theory is that the species evolved from a single female Cuban rock iguana bearing eggs which drifted across the sea during a storm or other such event.^[1]

Anatomy and morphology

The Blue Iguana is a large species of rock iguana with a body length of 20 to 30 inches and an equally long tail. It is the largest native land animal on Grand Cayman with a total nose to tail length of five feet and weighing as much as 30 pounds. Males are larger than females, with skin color from dark grey to turquoise blue when mature, whereas females are more olive green to pale blue. Young animals tend to be uniformly dark brown or green with faint darker banding. Their eyes are red in color and their distinctive black feet stand in contrast to the rest of their lighter overall body color.

Habitat

Comparison with other Cyclura species in the region strongly suggests there was once a coastal population of Blue iguanas, which was gradually displaced or extirpated by human settlements and the construction of roads. The Blue Iguana now only occurs inland, in natural xerophytic shrubland, and along the interfaces between farm clearings, roads and gardens, and closed canopy dry forest or shrubland. The interior population is believed to have been attracted to agricultural clearance and fruit farms which provide thermoregulatory opportunities, herbaceous browse, fallen fruit, and nesting soil, but this also brought the iguanas into contact with people and feral animals.
The iguanas occupy rock hole and tree cavity retreats, and as adults are primarily terrestrial. Younger individuals tend to be more arboreal. Hatchlings are preyed upon by the native snake ''Alsophis cantherigerus''. The adults have no natural predators, but fall victim to feral dogs. The age they would become an adult is typically 3 to 4 years. Natural longevity in the wild is unknown, but is presumed to be many decades (one captive in the USA died at 67 years of age).

Diet

Like all ''Cyclura'' species the Blue Iguana is primarily herbivorous, consuming leaves, flowers and fruits from over 100 different plant species. This diet is very rarely supplemented with insect larvae, crabs, slugs, dead birds and fungi.

Mating

Mating occurs in May, and 1-21 eggs are 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. Individuals are aggressively territorial from the age of about 3 months. Females occupy overlapping usage areas of the order of 0.6 acres, seemingly regardless of age, while males occupy progressively larger and more extensively overlapping usage areas, as they age and grow.

Conservation

Endangered Status

The Blue Iguana is critically endangered according to the current IUCN Red List. The population is restricted to the east interior of Grand Cayman, where it had been reduced to a critically low level prior to the first survey in 1938. The range has contracted significantly over the last 25 years, with many sites once populated now showing no signs of wild iguanas. The most recent surveys in 2005 indicated a total population in the range of 5-15 individuals. By 2005 the unmanaged wild population was considered to be functionally extinct. The species is one of the most endangered iguanas on Earth.^[2]
Restored free-roaming subpopulations in the QE II Botanic Park and the Salina Reserve numbered approximately 125 individuals in total, after a release in December 2005. The restored subpopulation on the QE II Botanic Park has been breeding since 2001, and the subpopulation in the Salina Reserve began breeding in 2006 after a nest of three hatched eggs was discovered in the wild.^[3][4] As of April 2007 after another large scale release there are 299 blue iguanas living in the wild with hundreds more being raised in captivity on Grand Cayman.^[5] As the wild population is above 250 individual animals, the IUCN may change it's status from Critically Endangered to Endangered.

Causes of Decline

Habitat destruction is the main factor threatening imminent extinction for this iguana. Land clearance within remnant habitat is occurring for agricultural purposes, road construction and for real estate development and speculation. Conversion of traditional croplands to cattle pasture is also eliminating secondary Blue Iguana habitat.

Predation and injury to hatchlings by rats, to hatchlings and sub-adults by feral and semi-domestic cats, and killing of adults by roaming dogs are all placing severe pressure on the remaining wild population. Road kills are an increasing cause of mortality. Trapping and shooting is a comparatively minor concern, but occasional trapping continues despite legal protection and sustained efforts in public awareness.
The Common Iguana, ''Iguana iguana'', from Honduras has become introduced and established on Grand Cayman and far outnumbers the endemic Blue Iguana.^[6] No direct negative consequences affecting the Blue Iguana are known, but the situation confuses public attitudes and understanding.
The wild population of Grand Cayman Blue Iguanas had been reduced from a near island-wide distribution to a barely viable, increasing fragmented remnant due to the combined influences of habitat conversion, historic hunting, the introduction of non-native species, and road kill. By 2005 any young being born to the unmanaged wild population were not surviving to breeding age, meaning the population was functionally extinct with only five animals remaining in the wild.

Recovery Efforts

Efforts for the Blue Iguanas are now being implemented by the Blue Iguana Recovery Programme, which operates under the auspices of the National Trust for the Cayman Islands, with local and international partners.
The conservation strategy involves generating large numbers of genetically diverse hatchlings, head-starting them to an age where survival in the wild is high, and using them to rebuild a series of wild subpopulations in protected, managed natural areas. A rapid numerical increase from a maximum possible number of founders, is sought to minimize loss of genetic diversity from the population bottleneck.
Once these restored wild subpopulations have reached the carrying capacity of their respective protected areas, release of head-started animals will be phased out and the sub-populations will be left to reproduce naturally. Guided by research and monitoring, control or eradication of non-native predators will be implemented to the degree necessary to allow young to survive to maturity, in sufficient numbers to maintain these subpopulations.
Restored subpopulations are already present in two non-contiguous areas (the Salina Reserve, and the QE II Botanic Park) and additional separate subpopulations will be restored in one or more other areas. The overall captive population, which must number at least 1,000 individuals, is likely to remain genetically fragmented in the long term. Individuals will be translocated between subpopulations to maintain gene flow, so the entire population remains a single genetic unit.
As a hedge against disaster striking the Blue Iguana population on Grand Cayman, an off-island captive population is being established in zoos in the USA. A minimum of 20 founder lines represented by at least 225 individuals, will be maintained by captive breeding.
Maintenance of Blue Iguanas in the wild will require active management into the indefinite future. To sustain this activity, a range of commercial activities will generate the sustained funding required, while an ongoing education and awareness effort will ensure continued involvement and support by the local community. Habitat protection is still vital as the Salina reserve can only sustain several hundred iguanas and land is expensive to purchase on Grand Cayman and deforestation pressures are extreme.
In October 2006, hatchlings were released into the wild for the first time to boost the species and help bring them back from the brink of extinction.^[7]

References

1. Re-enter the Dragon, , Georgina, Kenyon, New Scientist,
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External links

★ All about Cycluras

★ Entry at Cyclura.com

★ Blue Iguana Recovery Program (B.I.R.P.)

★ (BBC News) "SOS call for ancient blue iguana" 23 May 2005

★ (BBC News) "Breeding success for rare lizards" 27 October 2006

★ Revision to Species of Cyclura nubila lewisi, the Grand Cayman Blue Iguana

★ the National Trust for the Cayman Islands, the B.I.R.P's parent organization

★ the International Reptile Conservation Foundation, a major partner supporting the B.I.R.P

★ the Durrell Wildlife Conservation Trust, a major partner supporting the B.I.R.P.