Blue Iguana

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Blue iguana
CR

Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Order: Squamata
Family: Iguanidae
Genus: Cyclura
Species: C. lewisi
Binomial name
Cyclura lewisi
(Grant, 1940)

The Blue iguana (Cyclura lewisi) is a critically endangered animal that lives on the island of Grand Cayman. It is currently estimated that only a mere 25 animals still survive; the wild population is expected to be extinct within the first decade of the twenty-first century. The animals' demise is mainly driven by human pets (cats and dogs) and indirectly by the destruction of their natural habitat as fruit farms are converted to 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 the crtically endangered species. Some success with naturally-laid eggs has been reported.

Contents

[edit] Taxonomy

The Grand Cayman Blue Iguana, Cyclura lewisi Grant, is endemic to the island of Grand Cayman. Its closest relatives are Cyclura 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 doesn't seem to suffer the same lack of vitality that afflicts other such species. One theory is that the species evolved from a single Cuban female rock iguana bearing eggs which drifted across the sea during a storm or other such event.[1]

[edit] Behaviour

'''While it is likely that the original population included many animals living in coastal environments, 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 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. The age they would become an adult is typically 3 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).

[edit] 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.

[edit] Mating

Mating occurs in May, and eggs are usually laid in June or July, 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.'''

[edit] Conservation

[edit] 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 2002 indicate a total population in the range 10-25 individuals. By 2005 the unmanaged wild population was considered to be functionally extinct. The species is now the most endangered iguana on Earth.

Restored free-roaming subpopulations in the QE II Botanic Park and the Salina Reserve now number approximately 125 individuals in total, after a release scheduled 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.

[edit] 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, has become naturalized in Grand Cayman and far outnumbers the endemic Blue Iguana. 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 has 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.

[edit] 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 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.

[edit] References

[edit] External links

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