This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
More than a million tourists visited Jamaica last year. The vast majority of them traveled to the famous hotels and beaches of Kingston, the country's capital city. Few, if any, ventured about 25 kilometers to the west to the rocky limestone shores of Hellshire Hills. If they had, they might have seen something not many other people have ever had the opportunity to observe: the critically endangered Jamaican iguana (Cyclura collei).
But a small group of people gathering in Kingston this week know the Jamaican iguana quite well. The members of the IUCN SSC Iguana Specialist Group have spent the past 20 years working to preserve this rare lizard, which was feared to be extinct until it was rediscovered in 1991. The group's work since 1993 has been called one of the greatest successes in conservation science, but today the Jamaican iguana faces new threats and government indifference. Questions remain whether the Jamaican iguana will have another 20 years of opportunities.
Blame the mongoose
On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
The Jamaican iguana's decline began in 1872. That year the colonial government imported one of the predators that still plagues the iguana today, the Indian mongoose (Herpestes javanicus). Intended to stop white-bellied rats (Niviventer niviventer) from eating sugar-cane crops, the mongooses didn't stop there. They quickly spread across Jamaica, eating everything they could find. A Popular Science article from 1898 describes the ecological disaster: "It eats fruits of all kinds, fish, wild fowl, snakes, lizards, and crabs; and the once plentiful edible lizards and land crabs are now rarely seen. All young and tender life, both animal and vegetable, is included in its daily menu."
Full-grown iguanas can defend themselves from mongooses, but iguana eggs are another story. Most lizards lack the long-term memory to protect their young or their nests. After mother iguanas wandered away from their nests the invasive mongooses dined on iguana eggs and hatchlings. Before long the species had disappeared everywhere except Goat Islands, two smaller islets off the coast of Jamaica.
A temporary extinction
Jamaican iguanas persisted on Goats Islands until the 1940s when they too disappeared, probably due to invasive predators such as the goats for which the islands are named as well as feral cats. Scientists assumed, at this point, that the species had gone extinct.
But 1970 brought a surprise. A hunter's dog found—and killed—a single iguana in Hellshire Hills. Maybe the species wasn't extinct after all. It took until 1990 before another iguana was found, again by a hunter's dog. The wounded lizard was brought to Hope Zoo in Kingston, where resident herpetologist Peter Vogel recognized the importance of the find. A survey conducted soon after discovered a small population of probably fewer than 100 iguanas living in one of the few undisturbed areas of Hellshire Hills.
In 1991 Vogel watched two female iguanas lay their eggs. After they left he dug up the eggs and incubated them in his office. In 1992 he did something similar, corralling a nest site and capturing the hatchlings as they emerged. The two actions saved about 20 hatchlings. Now the real work would begin.
Crisis conservation
In 1993 the Iguana Specialist Group held its first meetings regarding the Jamaican iguana. A population habitat viability analysis revealed grim news for the species. "It was pretty clear that the only iguanas out there at the time were aging adults," says Tandora Grant, senior research coordinator at the San Diego Zoo and program officer of the Iguana Specialist Group. The Hellshire Hills areahad high populations of both mongooses and feral cats, both of which were taking their toll on iguana populations. "All the younger classes were basically eaten," she says. "We realized very quickly that this animal needed crisis conservation management."
Researchers hurriedly conducted more surveys and ramped up their efforts to bring some hatchlings back to Hope Zoo, where they would be kept safe from predators until they were old enough to defend themselves and survive in the wild, a process known as headstarting. Grant goes to Jamaica once or twice a year to check on the captive animals, giving them complete health assessments and tracking their progress. "We figure out who is fit enough and big enough to be released every year."
The first release of headstarted iguanas—one male and one female—took place in 1996. A few more young lizardswent back the next year, with numbers slowly climbing each year after that. The headstart program, meanwhile, had an almost immediate positive effect. "Within two or three years after our animals were released we saw them back at the nest sites reproducing themselves," Grant says. "So the number of breeding females has grown and grown and grown."
While all of this was going on, additional steps were taken to control mongoose access to the iguana nesting sites. A 10-kilometer circle of traps was set up, which catches mongooses "all the time," Grant says. Since mongooses a present throughout Jamaica it would be impossible to remove all of the mongooses from Hellshire Hills, but fewer now get into the nest sites.
Efforts have continued to expand. In 2006 the team decided to double the number of hatchlings brought into the headstart program from 20 to 40. The animals live at Hope Zoo for an average of five years until they reach optimal size and health. This April a record 52 Jamaican iguanas were released back into the wild.
Although it is unknown exactly how many Jamaican iguanas exist today, Grant reports that the number of known breeding females has grown by a factor of six. "We now have over 40 females nesting. This year we had a record count of over 300 hatchlings that emerged from the nest sites."
That success created a slight problem. The two existing iguana nest sites weren't big enough to accommodate the increased number of egg-laying females. "Hellshire is all just sharp, sharp rock," Grant says. "There are only the two open, naturally sandy soil sites that have the right amount of sun to let the eggs incubate. Females were occasionally digging up other females' eggs because there's a very finite amount of space to nest in." (The iguanas do occasionally nest in rock holes that have some dirt inside, but those are more open to mongoose invasion. Grant shared a series of camera-trap photos of a female iguana defending her rock nest against a mongoose, then getting bored and walking off. The next image shows the mongoose emerging from the nest with an egg in its mouth.)
To improve the situation, the team decided to create a third nest site. It wasn't easy. "Guys hauled in dirt on their backs for weeks and weeks and weeks," she says. The effort paid off: iguanas are now starting to nest at the artificial site as well.
The next 20 years – if we get that far
Despite the successes of the past 20 years, new threats have emerged. For one thing, people still enter Hellshire Hills to illegally cut down trees, which they then burn to create charcoal, an industry that employs 10,000 people in the area. The constant disturbance and accompanying hunting dogs could damage the fragile recovery of the iguanas.
For another, a long-planned goal of reintroducing Jamaican iguanas to Goat Islands now appears be on hold. "In 1993 we decided this would be one of the most important actions we could take," Grant says. Mongooses and other predators could be completely eliminated from the islands—goats have already been removed—providing a safe habitat for the iguanas. "Goat Islands would then be a source for reproduction and reintroduction back to Hellshire," she says, "because Hellshire will always be conservation dependent. If you had Goat Islands healthy and breeding it could be the headstart program instead of Hope Zoo."
The creation of a second population site is critical for the iguanas. "If you have a single population site, as we do now, you're always at risk. A secondary population is considered much, much less risky. That was going to be our crown jewel."
That doesn't look like it's going to happen. A Chinese company has proposed building a massive shipping hub on the islands. "It's not just Goat Islands they want to develop," Grant says. "There will also be shipping roads that will likely go right through where the iguanas are now. The whole program may be in jeopardy."
Simply moving the iguanas into a captive breeding program or to some other site (assuming one could be found) may not work, even if it becomes necessary. To date, Jamaican iguanas have only bred five times in captivity. Finding an open site that matches the climate of Hellshire Hills may not be possible.
"We'll have to wait to see what the Jamaican government has for ideas," Grant says, to protect the iguanas from both charcoal and the possible shipping facility. "I think the iguanas need a place to live, otherwise it's just a matter of time. We brought them back from extinction, but if there's not the will to keep them that way then it's just going to go right back to the where they were before."
All the same, Grant says she is trying to maintain hope and remains proud of the successes they have had over the years: "Every time I go to Jamaica I feel encouraged. This is a very good model of a program that can work, but it doesn't have a happy ending. Hopefully the book's not written yet."
Photos by Rick Van Veen, courtesy IUCN