“This is heaven for them,” says Young, who works in iguana conservation for the Virgin Islands National Parks Trust.
The 10-mile-long island has a population of less than 300 and is known for its extensive coral reefs, sandy beaches, and flock of flamingos.
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For millions of years, the iguana – up to five feet long and 15 pounds – was the largest vertebrate on this landscape. Despite the ferocity of adults, the iguana has been brought to its scaly knees by unlikely predators – feral cats that prey on juveniles.
Unlike the green surplus iguana, which is native to Central and South America and is widely introduced elsewhere, there are very few Anegada rock iguanas. By the 1990s, the pre-settlement population of about 10,000 iguanas had fallen to about 200. A simple conservation strategy has doubled the population since then. But recent setbacks show the limits of action.
Iguanas are particularly at risk when they emerge from eggs buried in sandy nests. Kelly Bradley, a conservation biologist at the Fort Worth Zoo who has worked with this iguana since 2001, estimates that up to half of the juveniles are taken up in the first week by native snakes and birds — Puerto Rican runners and American birds.
This is normal, these animals have evolved together for thousands of years. What upset the balance are non-native feral cats that are effective predators. They eat iguanas like popcorn, and very few iguanas survive to adulthood.
The cats probably arrived with colonial settlers in the 18th century and spread across the island. They have no natural predators, and as their numbers have grown, the iguana population has fallen to a critical threshold that requires human intervention.
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Near the bluff, Young hammers a few yards into the thorny brush, mopping the ground. He soon found a horseshoe-shaped scratch in the sandy soil. It doesn’t look like much, but it’s an old nest, where the iguana laid its eggs in the last year.
Each summer, he and Bradley painstakingly search for new nests dug by iguanas – tunnels that lead into deep chambers where they lay their eggs. It can take days to find a single nest.
When they find a nest, they put up large steel collars to hunt the emerging young, over 40 in a good year. They bring them to a “scoop” facility, which is cages where they are raised for several years until they are old enough to defend themselves against cats. Then they are released back into the wild.
The limits of human intervention
The program released 274 iguanas. Bradley tracked dozens of radios and more than 80 percent of them survived in the first two years after his release. But as long as cats remain plentiful in the Anegada, Bradley says the iguana will be a “conservation-dependent species” — one whose survival depends on human intervention. Recent events show the limits of such interference.
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In 2017, Hurricane Irma hit the city of Anegada before baiting season. The team did not catch any events that year. Then, while the island was still recovering from the hurricane, the British Virgin Islands were closed during the pandemic. Both events have limited Bradley’s fieldwork in recent years, and she and Young have collected fewer iguanas.
Walking between cages at the starting facility, Young says there have been as many as 64 captive iguanas in past years, but there are now 48. The facility is a project of the Virgin Islands National Parks Foundation, and features educational panels about iguanas and the island’s flora and fauna. When four American tourists arrive, Young shows them nearby.
One of the occasional visitors, who usually arrives barefoot with a small group of buddies, Young says, is Richard Branson. The billionaire owns nearby Necker Island, one of several smaller islands with populations from Anegada iguanas. There are now more iguanas on those islands than there are on the Anegada itself, but because they are all descended from just eight animals taken from the Anegada in the 1980s, they lack genetic diversity, so their conservation value is limited, Bradley says.
When most people think of iguanas, they only think of the green iguana, says Tandora Grant, a conservation program specialist with the San Diego Zoo Wildlife Alliance and the Iguana Specialist Group. iguana iguana. Its abundance obscures the scarcity of its cousins. As a family, iguanas are among the most endangered animals in the world, says Grant.
“There are 45 different species of iguanas, and only one is the type of pest that has been carried all over the place,” says Grant.
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There are 10 species of iguana in the genus Cyclura, all of which are endemic to the West Indies (another species became extinct sometime in the 20th century), and molecular analysis indicates that they all descended from the rocky iguana of Anegada. When sea levels fell during the glaciers, Grant says, the Anegada iguanas spread to other parts of the Caribbean. When the sea rose again, those iguanas became isolated on the islands and evolved into a distinctly different looking species.
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Other cyclora species in Jamaica and Grand Cayman also have starter programs to help them survive predation. This population is increasing, as is the population of Anegada. But Grant says that without the software, everything would fall apart again.
“We have to keep doing that until all the threats are really and truly mitigated, which is why it depends on conservation,” Grant says. “If we can get the money together, and the political will, to eliminate all the cats in Anegada, we can go home.”
“A head start isn’t a solution, it’s just a band-aid,” Bradley says. “We doubled the population in Anegada, and that sounds great, but it’s not enough. The reason for rejection has not been removed or addressed.”
The rock iguanas are still considered endangered by the International Union for Conservation of Nature (IUCN) and are listed on the Red List of Threatened Species.
Cassander Tetley O’Neill, director of the National Parks Trust of the Virgin Islands, says the ongoing spay and neuter project aims to reduce Anegada cat populations. She doesn’t envision a more ambitious cat control program right now, but says iguana conservation is a long-term priority for the agency.
“The state of preservation by the IUCN says it all,” said Tetley O’Neill. “They are extremely vulnerable and need protection for generations to come.”