T
he native-to-Hawaii copper striped blue-tailed skink, Emoia impar, is the latest vertebrate species to be declared extinct in the Hawaiian Islands, Robert Fisher, a biologist and research scientist for the U.S. Geological Survey’s Western Ecological Research Center in California, said Tuesday.
Emoia impar was last documented in 1963 along Kauai’s Napali coastline, Fisher said, before noting only three specimen were actually found there after 1940. That, he said, could indicate the skink for the most part disappeared from the Hawaiian Islands even earlier.
“At least through the mid-1960s, (the skink) was still found on the Napali coast, but that was only three records within this tiny stretch of land,” he said. “This was a species that was on every island in Hawaii and then went extinct on all but one of them about 100 years ago.”
The variety of skink is a sleek lizard with smooth, polished scales and a long, sky blue-colored tail. It was once common throughout the Hawaiian Islands’ lower elevations. The species is still found throughout Polynesia and Micronesia, he said.
Confirming the extinction follows about 20 years of field surveys that got under way in 1988, Fisher said. Despite the surveys, which included repeated visits to sites like the Napali coastline where the skink had been previously documented, the animal could not be located.
“We looked for them and couldn’t find any of them,” Fisher said, noting researchers combed Kauai, Oahu, Maui and Hawaii Island. “So, what happened?”
The introduction of the invasive big-headed ant in the early 1900s to Hawaii is likely the primary cause of extinction, Fisher said. Though no definitive data exists, Fisher said it can be concluded the skink, like other native animals, plants and insects, lacked natural defenses to the ant and thus fell victim.
“Ants are well known for causing declines or extinctions of reptiles by various mechanisms, including direct predation of adults or eggs, or indirectly by changing the food available for the reptiles,” according to the study’s findings published this month in the international conservation journal Oryx. “The timing of the introduction of the big-headed ant Pheidole megacephala and its documented effects on endemic invertebrates gives credence to their impact on numerous invertebrate and bird populations.”
He also added the skink may have fallen victim of “cryptic extinction,” which occurs when a species is confused with a similar species making its extinction go unnoticed for decades. In the case of the copper striped blue-tailed skink, it was likely that over the years people confused it with the blue-in-color rainbow skink, Lampropholis delicata, introduced in 1910 from Australia.
“Some people may have seen the bluish color and confused it for the ‘blue-tail,’” he said. “It’s possible then that people thought the (copper striped blue-tailed skink) had became real common.”
While the copper striped blue-tailed skink has now been extirpated from Hawaii, Fisher said he hopes the USGS determination will incite more accurate documentation and studies worldwide. More research, he said, could help halt the species from outright disappearing.
“This is a species widespread around the Pacific and it could be susceptible to the very same things” that happened in Hawaii, Fisher said. “If we continue to accurately document where these species occur then we can focus on those areas, better understand the resource and make sure we are conscious about what’s happening.”