Iguanas’ 8,000 km Voyage: A Remarkable Ocean Crossing

Why in the News ?

A new study reveals that Fijian iguanas likely traveled nearly 8,000 km from the Americas to Fiji on floating vegetation, making it the longest-known ocean crossing by a non-human vertebrate, solving a long-standing evolutionary mystery.

Iguanas’ 8,000 km Voyage: A Remarkable Ocean Crossing

About the Evolutionary Mystery:

  • Fiji and Tonga have native iguanas, despite all other species being found in the Americas.
  • Scientists have debated how these iguanas arrived in the South Pacific.
  • A new study suggests they crossed nearly 8,000 km on floating vegetation.
  • This would be the longest-known ocean crossing by a non-human vertebrate.

Genetic Evidence & Timeline

  • Researchers analyzed genetic samples from 14 iguana species.
  • Fijian iguanas’ closest relatives are desert iguanas from North America.
  • The species split about 30-34 million years ago, coinciding with Fiji’s formation.
  • Cold climate during that time made a land migration to Fiji impossible.
  • The estimated 3-4 month ocean crossing aligns with iguana hibernation periods.
  • Traveling on vegetation would have provided food for the herbivorous iguanas.
  • The study reinforces that long-distance dispersal played a key role in species evolution.

The Rafting Hypothesis:

  • “Rafting” refers to animals traveling across oceans on uprooted trees or plant debris.
  • Small creatures, especially invertebrates, are known to travel this way.
  • Among vertebrates, lizards and snakes can survive longer journeys due to slower metabolism.
  • In 1995, scientists observed iguanas rafting over 300 km between Caribbean islands.
  • Some researchers previously believed Fijian iguanas came from an extinct lineage that migrated via land routes.