A remote island at the very northern tip of Australia has been revealed as a tropical refuge for three species new-to-science — a gecko and two frogs — found nowhere else on Earth.
New research from James Cook University (JCU), recently published in Zootaxa, has identified these species on Dauan Island, a boulder-strewn, three-square-kilometre island in the far northern Torres Strait.
Covering an area about the size of a small city centre, the island harbours an extraordinary concentration of unique wildlife shaped by its isolation and rugged terrain at the edge of Australia.
"It's quite difficult to find obviously new species in Australia," said JCU lead researcher Associate Professor Conrad Hoskin.
"So, to find three in one spot, on this tiny little island, is wild."
Assoc Prof Hoskin said Dauan's unusual geology and location explain why these endemic species had remained undiscovered until now.
"A lot of the Torres Strait islands are quite flat and low, but because Dauan Island is actually the northernmost point of the Great Dividing Range, it sticks up out of the sea like a giant traffic cone," he said.
"This peak that makes up most of the island is made of millions of granite boulders, many the size of cars and houses, that are piled on top of each other, offering amazing hiding spaces for animals that needed a cooler, wetter environment to thrive.
"Species from New Guinea and Australia would have been marooned on this tiny island over time, survived and evolved there, while species in less rugged and more exposed places died out.
"And because the island is remote, small, and hard to explore, it's been sitting there doing its own thing, avoiding scientific attention."
Assoc Prof Hoskin identified one gecko and two frog species new-to-science, with all three adapted to life among the boulders.
The Dauan Island Gecko (Nactus simakal), named after the mountain that makes the island (Simakal pad), has a beautiful, banded pattern and long legs.
The small climbing Koeypad Frog Choerophyrne koeypad (koeypad = 'rocky mountain') was identified by its oversized toe pads, high-pitched call and lack of external ear for males, while the larger Gobakula Frog Callulops gobakula (gobakula = 'boulders') has a deep-croaking call and lives in cracks between the boulders.
Further surveys for the species, and for other unique biodiversity, will be led by the Torres Strait Regional Authority Rangers. These surveys will assess population sizes of the gecko and frogs and identify whether these species should be listed as threatened species.
Now known to have the highest number of endemic vertebrates of any island in Queensland, Dauan's unique biodiversity relies on strong biosecurity.
"All three species are restricted to this single island, so their future depends on keeping invasive species out," said Assoc Prof Hoskin.
Councillor of Dauan Island, Torenzo Elisala, said the findings celebrate both science and culture.
"The new discoveries highlight how special our island is," he said.
"Our community has been tucked away in the Guda Maluilgal nation for millennia, sharing the spiritual connection from flora to fauna to that of our ancestors who lived on these lands before us. We are connected to the land, sea and air.
"I want to acknowledge the work of Assoc Prof Conrad Hoskin and the Torres Strait Regional Authority Rangers for continuing to add biodiversity knowledge for the island.
"These discoveries are exciting to learn more about science and add to the tourism potential of the island."
The two new Zootaxa papers are available online here and here.
