Researchers have long wondered how iguanas reached Fiji, a remote island group in the South Pacific. Most iguanas live in the Americas, which are thousands of miles away from Fiji. Early ideas suggested that iguanas may have traveled through Asia or Australia before geological changes moved Fiji farther away. However, recent research suggests that iguanas crossed the ocean by floating on rafts of vegetation. This journey would have been over 5,000 miles (8,000 kilometers)—the longest recorded ocean voyage by a land-dwelling animal.

Genetic studies of 14 iguana species from the Americas, the Caribbean, and Fiji show that Fijian iguanas are closely related to desert iguanas from North America. Their evolutionary split is believed to have occurred about 31 million years ago. This supports the idea that iguanas drifted across the ocean rather than traveling by land. To test this, researchers created a model using genetic data, iguana distribution patterns, and environmental factors. The results showed that the most likely explanation was that iguanas floated to Fiji from North America. Desert iguanas’ ability to survive without much water and to eat plants likely helped them survive the journey. Learning about Fijian iguanas’ origins is important for conservation since native species are endangered, and invasive green iguanas threaten local ecosystems. These findings were published in Proceedings of the National Academy of Sciences.