THEY’RE BACK! Galápagos land iguanas became locally extinct on Santiago Island nearly 200 years ago. Conservationists have brought them home.

JUERGEN RITTERBACH/F1 ONLINE IMAGES/MEDIA BAKERY

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Operation Iguana

A rare lizard returns to an island in the Galápagos—nearly two centuries after it disappeared

AS YOU READ, THINK ABOUT what might cause an animal to disappear from a particular habitat.

Paula Castaño carefully climbs over the rocky shoreline of Santiago Island, a speck of land in the Pacific Ocean. She carries a bright-yellow crate filled with precious cargo in her arms. When Castaño reaches a small rise just beyond the beach, she kneels among the dried grass and dirt and takes off the crate’s lid. With a gentle prod, three large lizards scamper from the box and dash off into the underbrush. They’re the first land iguanas to set foot on this island since the 1800s.

“To see how they run into freedom right away was a very unique experience,” says Castaño, a veterinarian with the environmental group Island Conservation. “There are not really words to describe the feeling, knowing that this species went locally extinct from the island around 200 years ago.”

Paula Castaño carefully climbs over the rocky shoreline. She’s on Santiago Island, a speck of land in the Pacific Ocean. She carries a bright-yellow crate in her arms. It’s filled with important cargo. When Castaño reaches a small rise just past the beach, she kneels in the dried grass and dirt. Then she takes off the crate’s lid. With a soft prod, three large lizards run from the box and into the underbrush. They’re the first land iguanas on this island since the 1800s.

 “To see how they run into freedom right away was a very unique experience,” says Castaño. She’s a veterinarian with the environmental group Island Conservation. “There are not really words to describe the feeling, knowing that this species went locally extinct from the island around 200 years ago.”

ISLAND CONSERVATION

SET FREE: Castaño and workers with Galápagos National Park release iguanas on Santiago Island.

Land iguanas once thrived on Santiago—one of 19 small volcanic islands that make up the Galápagos archipelago (see Where in the World: Galápagos). When the famed naturalist Charles Darwin visited Santiago in 1835, the island was crawling with the 1 meter (3 foot)-long lizards. There were so many, in fact, that Darwin had trouble finding a clear patch of ground on which to pitch his tent. Soon after Darwin’s visit, though, the iguanas on Santiago disappeared. Today, fewer than 10,000 of the animals remain, scattered on other islands in the Galápagos.

Workers with Galápagos National Park, along with scientists like Castaño, have relocated more than 2,000 iguanas from other parts of the Galápagos to Santiago. It is the largest iguana repopulation effort in history. And it’s a big step toward restoring the biodiversity, or variety of life, that the Galápagos had before humans first arrived.

Land iguanas used to thrive on Santiago. It’s one of 19 small volcanic islands in the Galápagos archipelago (see Where in the World: Galápagos). The famous naturalist Charles Darwin visited Santiago in 1835. Then, the island was full of the 1 meter (3 foot)-long lizards. Darwin needed a place to pitch his tent. He had trouble finding a clear patch of ground because lizards were everywhere. But the iguanas on Santiago disappeared soon after Darwin’s visit. Today, fewer than 10,000 of them remain. They’re scattered on other islands in the Galápagos.

Galápagos National Park workers and scientists like Castaño are bringing the lizards back to Santiago. They’ve moved more than 2,000 iguanas from other parts of the Galápagos to Santiago. It is the largest effort ever to restore iguanas. And it’s a big step toward renewing the islands’ biodiversity. Its variety of life was much greater before humans first arrived.

NATURAL WONDER

The Galápagos Islands are part of Ecuador, a country along the west coast of South America. The islands are about 900 kilometers (560 miles) away from mainland Ecuador. The Galápagos formed millions of years ago when a series of underwater volcanoes erupted (see How the Galápagos Formed). The largest of the islands, called Isabela, is about the size of Rhode Island. One of the smallest, called Darwin, has an area of just one square kilometer.

The Galápagos is home to a rich array of unusual wildlife—much of which is endemic to the islands. These species don’t exist anywhere else on Earth. Some species in the Galápagos are even isolated to a particular island. There are three species of land iguana found only on the Galápagos. One is bright pink and lives near the rim of a volcano on Isabela. The Galápagos is also home to marine iguanas that swim in the sea and eat algae growing on underwater rocks.

The Galápagos Islands are part of Ecuador. This country lies along the west coast of South America. The islands are found about 900 kilometers (560 miles) away from the mainland. Millions of years ago, a string of underwater volcanoes erupted. That’s when these islands formed (see How the Galápagos Formed). Isabela is the largest of the islands. It’s about the size of Rhode Island. One of the smallest is called Darwin. It has an area of just one square kilometer.

The Galápagos is home to a rich collection of unusual animals. Many species are endemic to the islands. They don’t exist anywhere else on Earth. Some species in the Galápagos live on just one island. Three species of land iguana are found only on the Galápagos. One is bright pink. It lives near the rim of a volcano on Isabela. The Galápagos is also home to marine iguanas. They swim in the sea and eat algae growing on underwater rocks.

ISLAND CONSERVATION

CHECKUP: Castaño gives a vaccine to an iguana before it’s transferred to Santiago.

Giant tortoises also call the islands home. They can live for a hundred years and weigh as much as a horse. Sea lions and fur seals rest on the islands’ beaches, while huge whale sharks and playful dolphins swim in the surrounding crystal-clear waters. Plus, dozens of species of birds, including albatross, hawks, frigate birds, and finches, live and nest on the islands.

There was once an even greater amount of biodiversity in the Galápagos. But some of the islands’ species have become extinct. And a number of those that remain are critically endangered. People are to blame for much of the loss.

Giant tortoises also call the islands home. They can live for a hundred years and weigh as much as a horse. Sea lions and fur seals rest on the islands’ beaches. Crystal-clear waters surround the islands. Huge whale sharks and playful dolphins swim there. Plus, dozens of species of birds live and nest on the islands. They include albatross, hawks, frigate birds, and finches.

The Galápagos used to have even greater biodiversity. But some of the islands’ species have gone extinct. And some of those that remain are critically endangered. People are to blame for much of the loss.

ISLAND CONSERVATION

HOME SWEET HOME: The iguanas were released in habitats in which they were most likely to thrive.

UNINTENDED CONSEQUENCES

The unique plants and animals that populate the Galápagos Islands have long attracted visitors, including Darwin. He was the first person to make an in-depth survey of the species there. His observations of the variation among similar species living in different habitats on the islands helped him come up with his theory of natural selection. It states that organisms best adapted to their environment tend to survive and produce more offspring.

While Darwin’s stay in the Galápagos would have a huge impact on science, he and other visitors had a devastating effect on the islands. “Ships that visited the Galápagos often introduced new animals to the islands, such as rats, donkeys, pigs, and goats,” says Luis Ortiz-Catedral. He’s an ecologist—a scientist who studies how organisms interact with their environment—at Massey University in New Zealand. He helped officials at Galápagos National Park relocate iguanas to Santiago.

The unique plants and animals of the Galápagos Islands have long attracted visitors. One was Darwin. He was the first person to closely study the species there. He saw differences among similar species living in different habitats on the islands. That helped him form his theory of natural selection. It states that living things best adapted to their environment tend to survive and produce more offspring.

Darwin’s stay in the Galápagos would have a huge effect on science. But he and other visitors caused serious problems on the islands. “Ships that visited the Galápagos often introduced new animals to the islands, such as rats, donkeys, pigs, and goats,” says Luis Ortiz-Catedral. He’s an ecologist at Massey University in New Zealand. He studies how organisms interact with their environment. And he helped officials at Galápagos National Park move iguanas to Santiago.

Sometimes the introduction of new animals to the Galápagos was accidental. But other times, sailors left pigs, goats, and donkeys behind on purpose. The sailors planned to use them for food or for transport around the islands the next time they returned. Once the ships departed, the animals thrived and reproduced. They became invasive species that out-competed native animals—particularly the Galápagos land iguanas on Santiago. Rats developed a taste for the lizards’ eggs. And pigs, goats, and donkeys ate the plants that made up most of the iguanas’ diet. It didn’t take long for the iguanas to become extinct on the island.

The story of the iguanas on Santiago is common on other islands around the world. Although islands make up just 5 percent of land on Earth, they’re home to 75 percent of all bird, amphibian, mammal, and reptile extinctions. That’s in part because these isolated populations are often small and vulnerable. Even tiny changes to their ecosystem—the system of interactions between living and nonliving things—can have big effects.

Sometimes people brought new animals to the Galápagos by accident. But other times, sailors left pigs, goats, and donkeys behind on purpose. The sailors planned to return and to use them for food or for transport around the islands. After the ships left, the animals thrived and reproduced. They became invasive species that pushed out native animals. The Galápagos land iguanas on Santiago were hit hard. Rats liked to eat the lizards’ eggs. And pigs, goats, and donkeys ate the plants that the iguanas needed for food. Before long, the iguanas became extinct on the island.  

The story of the iguanas on Santiago happens on other islands around the world too. Islands make up just 5 percent of land on Earth. But 75 percent of all bird, amphibian, mammal, and reptile extinctions happen on islands. That’s partly because these remote populations are often small and delicate. They can be extremely affected by tiny changes to their ecosystem. That’s the system of interactions between living and nonliving things.

TUI DE ROY/MINDEN PICTURES

Marine iguanas feed on algae that cling to underwater rocks.

TURNING BACK TIME

Today, nearly all of the Galápagos is protected as a national park. Starting in 1997, the park began working to eradicate, or get rid of, most of the invasive species on Santiago. By 2006, the island was free of the pigs, goats, and donkeys that had contributed to wiping out land iguanas. But the island still struggled. Without iguanas, the island’s delicate ecosystem was off balance.

“Iguanas are great ecological engineers,” says Ortiz-Catedral. By eating only certain plants, the iguanas allow other trees, shrubs, and herbs to thrive on the island. This vegetation then provides shelter and food for other animals. The plants’ roots can also help prevent erosion by keeping soil from washing or blowing away.

Today, nearly all of the Galápagos is protected as a national park. In 1997, the park started working to eradicate, or get rid of, most of the invasive species on Santiago. Pigs, goats, and donkeys had helped wipe out land iguanas. By 2006, the island was free of these animals. But the island still struggled. Without iguanas, its delicate ecosystem was off balance.

“Iguanas are great ecological engineers,” says Ortiz-Catedral. The iguanas eat only certain plants. This allows other trees, shrubs, and herbs to thrive on the island. Then these plants provide shelter and food for other animals. The plants’ roots can also help prevent erosion. They keep soil from washing or blowing away.

Although land iguanas became extinct on Santiago, they survived elsewhere in the Galápagos. One of those places was a small island called North Seymour. Because there were fewer invasive species on that island, the iguana population grew to several thousand.

Ortiz-Catedral visited North Seymour in 2017. He realized the thriving population there presented an opportunity: “We could take thousands of iguanas from North Seymour without making a dent on the viability [chance of survival] of the population.” Because there were no longer competitors on Santiago, the lizards could be reintroduced there and have a shot at flourishing. With a lot of planning and hard work, officials at Galápagos National Park and researchers could help restore Santiago.

Land iguanas were extinct on Santiago, but they survived in other parts of the Galápagos. One of those places was a small island called North Seymour. Fewer invasive species lived on that island, so the iguana population grew to several thousand.

Ortiz-Catedral visited North Seymour in 2017. He saw the large population there and recognized an opportunity. “We could take thousands of iguanas from North Seymour without making a dent on the viability [chance of survival] of the population.” No invasive species were left on Santiago. That meant the lizards could be moved there and have a chance to thrive. Officials at Galápagos National Park and researchers could help restore Santiago. But it would take a lot of planning and hard work.

AMY TOENSING/NAT GEO IMAGE COLLECTION/NATIONAL GEOGRAPHIC CREATIVE

Giant tortoises are friendly but will withdraw into their shells if threatened.

MISSION ACCOMPLISHED

Before transporting iguanas to Santiago, researchers studied the North Seymour population carefully to determine whether the lizards could be moved without harm. Luckily, iguanas are very hardy animals, says Ortiz-Catedral. “They can survive months without water. When there is nothing else to eat, they can chew through the spiny stems of a cactus,” he says. “Moving them from one island to another is nothing.”

After animal safety, the next biggest concern during the relocation process was accidentally introducing invasive organisms to Santiago. So once the iguanas were captured on North Seymour, they were kept in a secure facility for several weeks. Castaño, the veterinarian, and her colleague Andrea Loyola made sure the animals didn’t have any parasites or diseases that they could spread to Santiago. Workers fed the iguanas a special diet to make sure they didn’t carry any seeds of invasive plants in their stomachs that could be deposited on the island in their droppings.

Researchers didn’t move iguanas to Santiago right away. First, they studied the North Seymour population carefully. They needed to learn whether the lizards could be moved without harm. Luckily, iguanas are very hardy animals, says Ortiz-Catedral. “They can survive months without water. When there is nothing else to eat, they can chew through the spiny stems of a cactus,” he says. “Moving them from one island to another is nothing.”

Animal safety was the biggest concern during the move. The next biggest was bringing invasive species to Santiago by accident. So after the iguanas were captured on North Seymour, they stayed in a secure building for several weeks. Castaño, the veterinarian, and her colleague Andrea Loyola watched the animals. They made sure the iguanas didn’t have any parasites or diseases that they could spread to wildlife on Santiago. Workers fed the iguanas a special diet with no seeds. That way, they didn’t carry any seeds of invasive plants in their stomachs. And their droppings wouldn’t plant these seeds on the island.

SVEN-OLOF LINDBLAD/LINDBLAD EXPEDITIONS VIA ISLAND CONSERVATION

Male frigate birds puff up their throats to attract mates.

Finally, the day came for the iguanas to head to Santiago. In early January, 2019, about 20 people loaded the iguanas into yellow crates and put them on a boat bound for two areas on Santiago. These locations had plentiful vegetation for the animals to eat and loose, sandy soil in which the iguanas could lay their eggs.

Finally, the day came for the iguanas to head to Santiago. In early January 2019, about 20 people loaded the iguanas into yellow crates. They put the crates on a boat headed for two areas on Santiago. These places had plenty of plants for the animals to eat. They also had loose, sandy soil. That’s where the iguanas could lay their eggs.

KEEPING TABS

For the next several years, Ortiz-Catedral and other scientists will keep track of the iguanas through regular trips to Santiago. An initial visit showed that the animals had survived the transfer and remained healthy. In future visits, the researchers will look for nests and other signs of breeding. These are the best indicators that the relocation effort was a success.

For the next several years, Ortiz-Catedral and other scientists will keep track of the iguanas. They’ll make regular trips to Santiago. Their first visit showed that the animals had survived the move and stayed healthy. In future visits, the researchers will look for nests and other signs of breeding. That’s the best way to tell if the move was a success.