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YOU might think the blue rock iguana has got it all. Good looks 鈥� a mythical dragon-like physique coupled with a complexion that changes from grey to azure at will; prime real estate 鈥� it hails from the idyllic Caribbean island of Grand Cayman; and no financial worries 鈥� after all, its home is a notorious tax haven. But the beast is in big trouble. There are only around 25 wild individuals left, making the blue iguana one of the most endangered reptiles in the world. Without help, extinction is certain.

Enter BIRP, the Blue Iguana Recovery Program. For the past decade this partnership of local and international conservation groups has been scrutinising every detail of the iguanas鈥� psychology and behaviour to work out what has gone wrong, and running a captive breeding programme to bring the species back from the brink. Such last-ditch efforts seldom succeed, but signs are that this one could be an exception, thanks to the peculiarities of the blue iguana. 鈥淭his is one species we can save,鈥� says Frederic Burton, who heads BIRP.

DNA analysis reveals that blue iguanas are descended from Cuban rock iguanas, having split off around 3 million years ago. One theory is that the species was established when a lone female, bearing eggs, drifted across 300 kilometres of open sea on a raft and fetched up on Grand Cayman during a hurricane or flood. Such a narrow population bottleneck would account for the low genetic diversity in today鈥檚 survivors. You might also think it is at the root of the current crisis, since inbred populations often lack vitality, but this does not seem to be the case. 鈥淣ot all species suffer equally from inbreeding, it seems, and these rock iguanas handle it well,鈥� says Burton.

Instead, the iguana鈥檚 population crash can be pinned on the usual suspects: humans. After Europeans established permanent settlements on the Cayman islands in 1741, the iguanas were driven inland into less hospitable areas. Early settlers sometimes shot blue iguanas to eat, as they are the largest land animals on Grand Cayman, growing up to 1.4 metres long and weighing 10 kilograms. People also killed iguanas because they thought they damaged crops. A steep decline in numbers came in the 20th century with increased road-building, coastal development and accelerating deforestation. The worst assault, however, has not come directly from people but from their pets: dogs and especially cats, which prey upon juvenile iguanas.

In 1988, a government-funded survey found that iguanas were so scarce in the wild that extinction seemed imminent, prompting the establishment of a captive breeding programme in 1990. But things went from bad to worse. In 1995, Burton and colleagues estimated that there were around 105 animals left in the wild. By 2001 numbers had dropped to just 25 or so. Drastic action was required. Later that year, an international group of conservationists met in Grand Cayman to draw up a recovery plan. The main aim was to increase the population to 1000 by reintroducing captive-bred animals into specially protected areas, so creating a self-sustaining and genetically viable population.

鈥淏lue iguanas are adaptable, consuming many plants brought to the islands by people. 鈥楽lugger鈥� even goes so far as to snack on slugs鈥�

The more that BIRP scientists have discovered about blue iguanas, the more hopeful they have become that they can achieve this goal. For a start, these reptiles are adaptable and learn fast. They are vegetarians, eating leaves, flowers and windfall fruits, but in the few hundred years since Europeans arrived in Grand Cayman they have expanded their natural diet of some 50 native plant species to over 130 by consuming new edible plants brought to the islands by horticulturalists and landscapers. One iguana, which the team have nicknamed 鈥淪lugger鈥�, even goes so far as to snack on slugs. As well as having eclectic tastes, they can also adapt to a man-made environment 鈥� they are as happy sleeping under a wooden shed as in a natural rock hole.

Although blue iguanas live alone and are generally solitary outside the breeding season, they are surprisingly sophisticated communicators. 鈥淭hey use a variety of different head bobs and other expressions, including changes to their body colour, tail lifting, winking and opening and shutting their mouths,鈥� says German nature-documentary film-maker and zoologist Dorothea Schwab, who has spent many months with the iguanas. Schwab has also observed that during the breeding season, males use their tongues to pick up scents from other iguanas鈥� droppings, to keep a track of each other and of females.

As well as being intelligent and adaptable, blue iguanas are 鈥渉ard-wired鈥� to behave in certain ways that are crucial for their survival. 鈥淗atchlings receive no parental care whatsoever,鈥� says Burton. In the wild, females bury their eggs in a hole around 30 centimetres underground, where they hatch between 65 and 100 days later, depending on the temperature. 鈥淭hey have to dig their own way out of the nest and avoid snakes. They are instinctively afraid of snakes and run for trees if they see them,鈥� says Burton. 鈥淭hermoregulation, a fundamental part of all cold-blooded creatures鈥� lives, is also instinctive.鈥� Such hard-wired behaviours have made it relatively easy for the BIRP scientists to reintroduce young iguanas into the wild, knowing they will be able to fend for themselves.

Neither is breeding a problem for blue iguanas. In the wild they are quite capable of reproducing without assistance, with females producing between one and 19 eggs depending on their size and maturity. Where things start to go terribly wrong, the scientists have discovered, is in the two years after hatching, when juveniles fall prey to introduced predators. A primary goal of the captive breeding programme is to protect the young during this vulnerable period.

So far, BIRP scientists have successfully incubated 287 eggs and are now rearing more than 80 young a year. There are 190 iguanas in the programme, 30 of which have been released into a protected reserve in Queen Elizabeth II Botanic Park in the north-east of the island. Last December the scientists released a further 21 animals into a neighbouring site at Salina Reserve. Iguanas in both populations have mated successfully. 鈥淭he captive breeding programme is going from strength to strength,鈥� says Burton. 鈥淥ur monitored releases are working brilliantly so far.鈥� But with just 27 hectares of suitable habitat currently designated as reserves, and these approaching their capacity, a major task is to find more areas that can be fenced off from predators.

Meanwhile, the benefits of an increased insight into iguana biology are stretching way beyond Grand Cayman. It will also give a boost to blue iguanas in zoos around the world, which have always had great difficulty breeding. Burton is collaborating with three zoos in the US in an attempt to remedy this by identifying the environmental conditions in which the animals breed best in the wild, so that these can be replicated in zoos. This is not just about better window-dressing for zoo visitors: the zoo animals are an important source of genetic diversity in this already highly inbred species. A healthy zoo population will also act as a fallback should disaster befall the species in the wild.

For now, though, things are looking up for the blue iguana. 鈥淚f we can protect enough habitat and maintain it free of unnatural predators, there is every reason to hope we can give the blue iguanas their future back,鈥� says Burton.