Look-alike lizards threaten Critically Endangered Lesser Antillean Iguanas

A tropical island may seem like a haven isolated from the outside world. But for the Lesser Antillean Iguana (Iguana delicatissima), being surrounded by water isn’t always enough to protect it from threats to the species’ survival — like a rival iguana swept in by a hurricane.

 In 1995, Hurricane Luis left a trail of destruction across several Caribbean islands. On Anguilla, in addition to its more visible damage, the storm brought some Green Iguanas (Iguana iguana)

 to the island’s shores from nearby Guadeloupe. Native to Central and South America, this species had been introduced in Guadeloupe and quickly made itself at home in Anguilla as well. But as Green Iguanas took over, they did so at the expense of the Lesser Antillean Iguana, a native species that is now classified as Critically Endangered by the IUCN Red List of Threatened Species.

“Generally when Green Iguanas turn up, the native iguana species have disappeared within 20 years,” says Jenny Daltry, Caribbean Alliance director between Re:wild and Fauna & Flora International. “One of the alliance’s goals is to prevent these extinctions from continuing.”

The Caribbean islands represent less than 1% of the Earth’s land area but have accounted for 10% of the world’s bird extinctions, 38% of the world’s mammal extinctions, and over 65% of the world’s reptile extinctions since European colonization began.

Rising Threats

The Lesser Antillean Iguana was once common across many islands in the Eastern Caribbean. Because they are seed dispersers, these large lizards play an important role in maintaining forest cover across multiple islands.

However, their numbers have declined rapidly in recent years. Many threats have likely contributed to this decline, including deforestation, hunting, disease, and inbreeding depression, which becomes a bigger risk as the population drops. In addition, a fear of reptiles is common among locals.

But in most places, the invasive Green Iguanas pose the most urgent threat to the native Lesser Antillean Iguanas. Not only can they spread disease to the native iguanas and displace them from their habitat, but Green Iguanas can actually breed with Lesser Antillean Iguanas, which results in hybrid animals. The Green Iguanas are also more prone to raiding crops, thus angering farmers and jeopardizing their livelihoods. 

While closely related, replacing one iguana species with another disrupts the islands’ ecological balance. You can’t simply swap species.

“It actually doesn’t work like that, because the native iguanas have very different behaviors,” says Farah Mukhida, executive director of the Anguilla National Trust “The native iguanas don’t cause those types of agricultural problems, and are not a nuisance, whereas the Green Iguanas are. They also have far more offspring than the native iguanas, so their population really can explode and become uncontrollable. It’s always a better balance when you have just  native wildlife.”

In less than two decades, the Green Iguana has decimated Anguilla’s population of Lesser Antillean Iguanas. The only large island where the native species still has a healthy population is Dominica, often called the “nature island of the Caribbean” due to its high forest cover. But invasive iguanas have been spotted here too, meaning there is no time to lose.

“There’s a lot of pressure on Dominica because if the invasive species were to take over Dominica, or if something else were to happen and we lose our native species, that is going to be one of the final nails in the coffin for Lesser Antillean Iguanas across the region,” says Jeanelle Brisbane, founder of WildDominque, a Dominican NGO.

No conservation in isolation

The new Caribbean Alliance — a partnership between Re:wild and Fauna & Flora International — seeks to raise the profile of the Caribbean Islands as one of the most biologically diverse and threatened parts of the world. This collaborative working relationship also aims to expand teamwork between islands to accelerate conservation successes in the region. 

“We’re still acting very much like individual islands,” says Brisbane. “We can’t just manage a species on one island if it exists throughout the region. If one island is suffering, we can’t leave them to suffer. So, when we got a call from Anguilla to assist in managing their Lesser Antillean Iguana population, we were very happy to respond to that call because they’re our sister island, and it’s all for the common good of saving the species. You can’t do it in isolation.”

Reintroduction in Prickly Pear East

 In 2016, the Anguilla National Trust--with assistance from Fauna & Flora International--took emergency action to save the Lesser Antillean Iguana. After rounding up all the native iguanas they could find (only about 23), making sure they were free of disease and conducting genetic testing to make sure none of them were hybrids, the individuals were released on a small privately-owned offshore island called Prickly Pear East. Because the island was well-protected and clear of invasive iguanas, it is a safe place for the native species to breed and revive its population without pressure from the usual threats.

“As a new population, 23 isn’t really enough. Some of those animals are probably closely related, and one worry is if there are not many of them, then there will be inbreeding problems. We could end up with animals becoming very sick and not breeding very well because they’re too closely related,” says Daltry.

This program got a boost after a 2018 meeting became a major turning point for efforts to save the species by bringing together iguana conservationists from across the region. Instead of working independently, the participants soon discovered that they all brought different kinds of expertise to the table. 

“We discovered one island was really good at catching and monitoring the iguanas,” says Daltry. “Another island was really good at controlling the invasive species, another island was really good at public education and awareness.”

The connections forged at the meeting eventually led to Brisbane and WildDominique facilitating the capture and donation of 10 of Dominica’s native iguanas to Anguilla’s Prickly Pear East reintroduction program in 2021 in order to increase the population’s gene pool. This took lots of planning and paperwork; when the Anguilla team came to help capture the new iguanas, Brisbane’s iguana team took them up and down the Dominican coast looking for the best individuals to transfer to the new habitat, considering factors such as size, gender balance, overall health and genetic diversity.

In return, Anguilla has been assisting Dominica with their efforts to combat the invasive Green Iguanas, which are starting to appear more frequently on Dominica. Brisbane herself saw her first invasive iguana on the island shortly after the 2018 meeting, where she had learned just how much the species had devastated neighboring islands.

Although exact iguana numbers are tricky to assess on highly vegetated islands, the Lesser Antillean Iguana population on Prickly Pear East appears to be growing steadily, with large numbers of juveniles seen on recent surveys. Eventually, the Anguilla National Trust hopes to expand the reintroduction program to other islands, and eventually back to the main island itself. Without the addition of the Dominican iguanas, it’s unlikely this project would have been as successful.  

The collaboration between Dominica and Anguilla is just the beginning. In fact, each island home to Lesser Antillean Iguanas is starting to strategize and work together to save the species across the Caribbean. With dedicated support from local champions from both the Anguilla National Trust and WildDominque, there’s growing hope that these unique reptiles will beat the odds and retain their vital place in the forests of the Caribbean.