Once thought extinct, the azure-tailed skink is rediscovered on Hāmākua sea cliffs

“Lost treasure lizards”: Professor Emeritus of Biology Bill Mautz has authored an article about finding colonies of a long-lost Hawai‘i skink on the sea cliffs of Hāmākua.

Bill Mautz with inset of skink
An archived photo of Bill Mautz with inset image of azure-tailed skink on Hawai‘i Island. (Skink photo by Gary L. Miller).

By Susan Enright

Despite retiring from teaching in 2019, Bill Mautz, professor emeritus of biology at the University of Hawai‘i at Hilo, continues his work investigating a Hawai‘i lizard once thought to be extinct. His findings about the azure-tailed skink are published in the December 2021 issue of Herpetological Review.

Mautz’s research interests are in animal physiological ecology and environmental toxicology. Before his retirement from UH Hilo in 2019, he combined his research in physiology and ecology in projects with undergraduate students studying biology and graduate students in the tropical conservation biology and environmental science master of arts program.

Mautz was also monitoring the island night lizard in California as a private consultant to the U.S. Navy. His work on xantusiid lizards and island biology was part of a long-term demographic study of the federally listed threatened island night lizard on San Clemente Island, California.

Now he has authored an article about finding colonies of the Hawai‘i skink on the sea cliffs of Hāmākua. In “The Azure-tailed Skink, Emoia impar, Remains Extant on Hawai‘i Island, USA,” Mautz reports “that a sea-cliff-top population of E. impar is present at Ninole, Hawai‘i Island, based initially on a photograph taken on 8 January 2017.”


Lizard with blue tail and orange stripes down head and back.
An azure-tailed skink (Emoia impar) on a pandanus leaf in Nīnole, Hawai‘i. (Gary L. Miller)

The once common Hawaiian populations of azure-tailed skinks drastically declined in the islands during the past 100 years. Researchers documented reduction of populations on all the major Hawaiian Islands, and in the 1960s, the last single specimen catalogued was from Kaua‘i. Researchers believed the species was likely extinct in the Hawaiian Archipelago. Fast forward to 2000 when the reptile was rediscovered on Mokapu islet off Molokai. And now Mautz has confirmed there are colonies of the lizard on Hawai‘i Island.

“I first became aware of this lizard on Hawai‘i Island in 2017 when Aaron Mickelson, a former student in UH Hilo’s tropical conservation biology and environmental science graduate program, sent me a photograph taken by Gary Miller and asked me if I knew what this lizard was,” says Mautz about the image taken near Nīnole of an azure-tailed skink, easy for the biologist to identify with its distinctive blue tail and stripes. “I said I know what it is, but it is not supposed to be here anymore.”

Mautz notes that the little brown skinks common in Hilo backyards are a different species called the delicate skink. They may have a slate-colored tail but it is not a true blue. “The azure-tailed skink also has a stripe over the top of its head,” he says.

Once he saw the photo, Mautz joined Miller for a hike to the lizard population, which is confined to a small grove of pandanus trees at the top edge of the ocean cliffs near Nīnole on the Hāmākua Coast. Mautz explains that cliff-edge populations of rare wildlife restricted there by ecological pressures like habitat destruction and invasive predators and competitors are vulnerable to local extinction.


A group of skinks bask in the sun in pandanus leaf litter.
Seven azure-tailed skinks (Emoia impar), once thought to be extinct, bask in the sun in pandanus leaf litter, Nīnole, Hawai‘i. (Gary L. Miller)

In addition to habitat destruction, says Mautz, the disappearance of azure-tailed skinks across the Hawaiian Archipelago over the past 100 years could be due to feral cats, rats, mongoose, and invasive species of ants.

“The other difficulty for cliff edge populations of wildlife on Hawaiʻi Island is that residential property development is rapidly proceeding on the Hāmākua Coast,” Mautz notes. “Newer developers favor ocean views over small farms and set landscaped houses close to the edge of the sea cliffs.”

Mautz says that it is not known if the azure-tailed skinks are restricted to pandanus tree groves and if there are other populations of the lizards elsewhere on the island.

“There is a rumored sighting of a blue-tailed skink in pandanus forest in the Kohala Mountains,” he says. “I have been searching the fragmented cliff-top pandanus groves on the Hāmākua Coast and Kohala Mountains for more lost treasure lizards, so far without luck.”


By Susan Enright, a public information specialist for the Office of the Chancellor and editor of UH Hilo Stories. She received her bachelor of arts in English and certificate in women’s studies from UH Hilo.