About 34 million years ago, iguanas sailed 5,000 miles from western North America and settled in Fiji. It’s not uncommon for iguana species to hop a natural raft and drift to a new island, but according to new research published in Proceedings of the National Academy of Sciences, this may be the “the longest known transoceanic dispersal of any terrestrial vertebrate.”

“We found that the Fiji iguanas are most closely related to the North American desert iguanas, something that hadn’t been figured out before,” said lead study author Simon Scarpetta, a herpetologist, and paleontologist who is a former postdoctoral fellow at University of California Berkeley, in a press release. 

Iguanas and Overwater Dispersal 

Most life that finds its way to newly-formed islands typically comes via overwater dispersal. Organisms such as plants and animals, and even humans, find their way to these new islands and take up residence. On these islands, new ecosystems and species form something that researchers such as Charles Darwin have always found fascinating. 

Different iguana species are found across the globe, and some are endemic to specific regions, like the Galapagos and Fiji. In previous research, scientists believed that the native Fiji iguanas were descendants of a different iguana species that had gone extinct, however, the new study suggests otherwise. 

Read More: Scuba-Diving Lizards Create an Air Bubble Over Their Heads to Swim Underwater

Fiji Iguana Lineage 

According to the study, it would appear that the iguana’s arrival to Fiji coincides with the archipelago’s formation. By studying the genetic divergence of Brachylophus, Fiji’s iguana species, from their closest relative, Dipsosaurus, North American desert iguanas, the research team determined that iguanas made it to Fiji about 30 million years to 34 million years ago. 

“[The] lineage of Fiji iguanas split from their sister lineage relatively recently, much closer to 30 million years ago, either post-dating or at about the same time that there was volcanic activity that could have produced land,” Scarpetta, who is now an assistant professor at University of South Florida in the Department of Environmental Science added in a press release.

Other theories suggest that the iguanas came from other parts of South America or even Australia, but there is no fossil evidence to back this up. It’s possible that a large storm swept the iguanas out to sea and they survived the journey because they could have gone long periods of time without food or water. 

“You could imagine some kind of cyclone knocking over trees where there were a bunch of iguanas and maybe their eggs, and then they caught the ocean currents and rafted over,” Scarpetta said in a press release.

The study authors also note that if it were upturned trees that brought the iguanas to Fiji, the trees may have provided food. 

The Genetic Outliers 

Besides being expert sailors, it turns out that Brachylophus is an outlier among other iguana species. They’re also endangered due to exotic animal poaching, habitat loss, and predation from an invasive rat species. 

To better understand where Brachylophus fits in the iguana family tree, Scarpetta analyzed genome-wide sequence DNA from genes and tissues of over 200 iguanian specimens. From there, he determined that Brachylophus and Dipsosaurus were most closely related. 

“Iguanas and desert iguanas, in particular, are resistant to starvation and dehydration, so my thought process is if there had to be any group of vertebrate or any group of lizard that really could make an 8,000-kilometer (5,000-mile) journey across the Pacific on a mass of vegetation, a desert iguana-like ancestor would be the one,” Scarpetta said in a press release.

Read More: Why Is Darwin Island in the Galapagos Off-Limits to Visitors?

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A graduate of UW-Whitewater, Monica Cull wrote for several organizations, including one that focused on bees and the natural world, before coming to Discover Magazine. Her current work also appears on her travel blog and Common State Magazine. Her love of science came from watching PBS shows as a kid with her mom and spending too much time binging Doctor Who.