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Researchers from the U.S. Geological Survey, Taronga Conservation Society Australia, The National Trust of Fiji and NatureFiji-MareqetiViti have discovered a new species of banded iguana.

Illustration of Fijian Gau iguanas.
Illustration of Fijian iguanas.(Credit: Cindy Hitchcock, USGS Western Ecological Research Center. Public Domain)

The new species of lizard, Brachylophus gau, is one of only four living species of South Pacific iguana, and is restricted to the island of Gau, Republic of Fiji. The scientists describe this new addition in an article released with the journal Zootaxa.

The first known recording of iguanas on Gau Island dates back to an expedition in the mid-19th century. In 1854, the survey ship HMS Herald carried Scottish naturalist John MacGillivray to the Fiji islands, where he chronicled his encounters with native wildlife in his journal.

Authors of the article in Zootaxa compared copies of MacGillivray’s journal entries with their own observations. They collected live iguanas, preserved specimens, and compared photographic evidence with specimens at the University of the South Pacific Herpetology Collection, Suva, Fiji and the British Museum of Natural History, London.

The Gau iguana is noticeably different from its peers in physical appearance. It has unique color patterning, including green throats on both males and females, whereas males of other iguana species never have solid green throats. Additionally, it is the smallest known of the species in Fiji, being 13 percent smaller than the next largest species, and 40 percent smaller than the largest species.

Currently, Pacific iguanas face threats from habitat loss and invasive species such as mongoose, feral cats, rats and goats. Gau Island, Fiji’s fifth largest island with an area of about 130 square kilometers, is about half forest, and half a mix of grasslands, plantations and forests regrown following timber harvests. The Zootaxa study indicated that Gau iguanas mostly inhabit the island’s large inland forests, which remain relatively intact. Gau’s coastal forests were more degraded than those found at mid-elevations and hosted smaller numbers of these iguanas.

“These types of discoveries continue to surprise us in Fiji, where we are showing a much richer reptile fauna than was previously known to exist,” said Robert Fisher, research biologist with the USGS and lead author of the study.

“As the national statutory authority for conservation, the National Trust of Fiji has the responsibility for understanding the biodiversity and ensuring its persistence for future generations,” said Jone Niukula, conservation officer with the National Trust of Fiji, “these iguanas are some of the most amazing species within our country and knowing how many species exist is a priority for us.”

Photo of a female Gau iguana
(Credit: Mark Fraser. Public domain.)

“We still don’t know exactly how many species of iguana there might finally be on Fiji’s 300 islands,” said Peter Harlow, terrestrial biologist with Taronga Conservation Society Australia. ”Many islands are still to be surveyed.  On my first trip to Fiji there was just a single known species, and today we have four species.”

Dick Watling, NatureFiji-MareqetiViti, stated “I knew that Gau Island contained many biodiversity secrets in my 35 years of working out there, and am gratified to see this unexpected one resolved.”

With further study, researchers can establish a more comprehensive understanding of the iguana’s range, and identify priority areas for conservation. Future directions include continuing the NatureFiji-MareqetiViti collaborations with local communities to conserve both the Gau iguana and Gau forest habitats that are key to maintaining the critical species endemic to this island.