An island in the Galápagos reintroduced iguanas after nearly 200 years of extinction

A species of iguana that went extinct nearly 200 years ago on one of the Galápagos Islands appears to be making a comeback, with some help from a team of conservationists.

The last person to spot a Galápagos land iguana on Santiago Island in Ecuador was Charles Darwin in 1835. When an expedition team from California arrived in 1906, the iguanas were nowhere to be found.

And though this kind of iguana can still be found on the other Galápagos Islands, it's believed to have been extinct on Santiago for the past 187 years — until now.

A team of scientists and park rangers discovered new lizards of various ages while walking the island in late July, which suggests the species has been successfully reintroduced. And according to Jorge Carrión, director of conservation of the Galápagos Conservancy, the ecosystem is thriving as a result.

The evidence is in the details, he explained. Seeing lizards of different ages and coming across unmarked specimens means the iguanas are breeding in their natural environment.

Before joining the Galápagos Conservancy, Carrión worked for the Galápagos National Park Directorate, the caretakers of the islands' ecosystems and resources. The GNPD is also the authority spearheading the iguana reintroduction project, with funding and assistance coming from the Conservancy.

He said the collaborative has released more than 3,000 land iguanas on the island since January 2019.

Conservationists decided to reintroduce the land iguana after carefully considering how a return of the species would affect the ecosystem. These lizards are what's known as an engineering species, like the Galápagos giant tortoise, in that they play a critical role in maintaining a healthy balance in an ecosystem.

As the primary herbivores on the Galápagos Islands, the land iguanas and tortoises spread seeds across the landscape and help model the plant communities, Carrión explained. Their movement patterns also create open spaces used by other animals.

"This kind of species are critical for ecosystem in general," Carrión said. "In this case it was the justification for the reintroduction of land iguanas, to [return] the natural dynamic to Santiago Island. When engineer species are not present, many imbalances occur in the ecosystem."

What caused the iguanas' extinction?

It's believed that the Galápagos land iguanas were wiped out by invasive species, including feral pigs, cats, goats and donkeys. These unwelcomed animals were introduced to some of the islands, including Santiago, by whalers and other mariners. They wreaked havoc on the ecosystem, devouring plants other species relied on, and some even ate the iguanas.

That is why scientists had to rid the island of non-native animals before the iguanas could be reintroduced. This was accomplished over a nine-year period through the Galápagos Conservancy's Project Isabela, which was completed in 2006.

Carrión said he and his colleagues believe they have learned an important lesson through the reintroduction of the land iguanas: if you remove the source of the ecological disturbance (the invasive species in this case), the ecosystem can recover and return to its natural dynamic.

The Galápagos Conservancy and the National Park Directorate are also working together to reintroduce the giant tortoise on another island. The native tortoise has been extinct on Floreana Island since the 1800s, according to the Galápagos Conservancy, and reintroduction and breeding efforts began in 2017.

The ecosystems found on the Galápagos Islands are home to some of the most fascinating plants and animals in the world. The islands were made famous largely due to Darwin and his 1835 expedition, according to the Conservancy, which led to his theory of evolution by natural selection.

Copyright 2022 NPR. To see more, visit https://www.npr.org.