Reptiles
Grand Cayman Blue Iguana
Cyclura lewisi · also called grand cayman blue iguana, blue iguana
The Grand Cayman blue iguana is a large, heavy lizard that turns a startling electric turquoise when it warms in the sun. Twenty years ago it was as good as gone — a 2002 count found perhaps 15 to 25 left in the wild, and extinction was forecast within a decade. A captive-breeding programme reversed that, and today more than a thousand blue iguanas live on Grand Cayman again.
Overview
The Grand Cayman blue iguana is endemic to Grand Cayman, in dry shrubland, dry forest, and rocky interior country, now concentrated in protected reserves. It is one of the largest lizards in the Americas, reaching about 1.5 m and 14 kg, grey to tan at rest and vivid turquoise-blue when warm or displaying. It is a herbivore and an important seed disperser for native plants.
From the edge and back
By 2002 the wild population had crashed to an estimated 10–25 animals, driven down by dry-forest clearing, road deaths, feral cats, dogs, and rats, and pressure from introduced green iguanas. Extinction in the wild was projected for around 2012.
The Blue Iguana Recovery Programme took founders into captivity, hatched the eggs safely, raised the young for about two years until predators could no longer kill them, and released them into fenced, managed reserves. Combined with predator control, this rebuilt the population to well over 1,000, and the IUCN downlisted the species from Critically Endangered to Endangered in 2012.
A very long life
Blue iguanas are among the longest-lived lizards known — one captive individual reached 69 years. That longevity means even a few founder animals can keep breeding for decades, which is part of why the recovery has worked.
Status
The Grand Cayman blue iguana is Endangered but increasing, still dependent on protected reserves, ongoing predator control, and captive breeding.
Grand Cayman Blue Iguana: common questions
How close did the Grand Cayman blue iguana come to extinction?
Very close. A thorough survey in 2002 could find only an estimated 10 to 25 blue iguanas left in the wild on Grand Cayman, scattered and mostly old, with little successful breeding. Modelling suggested that at that rate the animal would be extinct in the wild by around 2012. It was one of the most endangered lizards on Earth, and its situation was widely used as an example of how an island reptile can be quietly wiped out by a combination of habitat loss and introduced predators before anyone acts.
How was it saved?
Through a captive-breeding and headstarting programme, the Blue Iguana Recovery Programme, run on Grand Cayman with international support. Remaining wild adults and existing captive animals were used as founders. Their eggs were hatched in safety, and the young were raised in predator-proof enclosures for about two years, until they were large enough that feral cats and dogs could no longer easily kill them. They were then released into fenced and managed reserves, chiefly the Salina Reserve and the Queen Elizabeth II Botanic Park. Combined with predator control and habitat protection, this rebuilt the population from a couple of dozen animals to more than a thousand.
Why is it blue?
The blue colour is a social and thermal signal rather than camouflage. At rest and when cool, a blue iguana is mostly grey or tan, which blends with rock and leaf litter. As it warms in the sun and especially when a male is displaying to rivals or to females, the skin shifts to a vivid turquoise-blue, most intense on the forebody and legs. The display colour advertises the animal's size, health, and readiness to defend a territory. Females and juveniles show the colour too but usually less strongly.
How long do blue iguanas live?
Longer than almost any other lizard. Blue iguanas are slow-growing and slow to mature, and in captivity they routinely reach several decades. The best-documented case is an animal that lived to 69 years, which is among the longest confirmed lifespans recorded for any lizard. This longevity is part of why the recovery programme works — even a small number of founder animals can keep breeding for a very long time, and released iguanas have many years in which to reproduce in the wild.