Tuatara once ranged throughout New Zealand before rats, cats, and stoats—introduced by human colonizers—wiped them out.
Now the reptiles are limited to remote, mostly small islands around the top of New Zealand's South Island and off the eastern coast of the country's North Island (map of New Zealand).
"On North Brother, most nesting is in very shallow soil, and there's already a male bias in the population," Nelson said. "There's probably no way to naturally resurrect that."
So scientists are gathering eggs from North Brother and from nearby Takapourewa, or Stephens Island, and raising them in artificial incubators.
"We can dial in whichever sex we like," Nelson said.
Another captive population is being reared in California's San Diego Zoo.
Hatchlings are reared in captivity before being introduced to other islands as part of an effort by New Zealand's Department of Conservation to reintroduce the tuatara to its former haunts.
But Alison Cree, a senior lecturer at the University of Otago in Dunedin, New Zealand, says rising temperatures are not the only threat climate change poses to tuatara.
"There are the potential impacts of rising sea levels, coastal erosion, and habitat loss in general," Cree said.
Researchers plan to release tuatara in a sanctuary protected by a specially designed predator-proof fence at Orokonui, near Dunedin. The site is well south of the tuatara's current distribution, and Cree hopes it will buy time for the species as northern New Zealand warms in the coming decades.
"Eight populations of northern tuatara live on islands of 5 hectares [12 acres] or smaller, often with only two or three hectares [5 or 7 acres] of suitable habitat," she said. "The higher the sea level, the smaller that will get. We're already concerned about the long term future of those populations—there are so few animals there already."
Saving the tuatara is a matter of pride among New Zealand's indigenous groups. The animals are revered by the Maori as a taonga, or treasure.
Glenice Paine, the Te Atiawa Maori tribe's resource management officer, says something irreplaceable will be lost if tuatara can no longer survive in the wild. The archaic reptile is a living link with the ancestors of her people.
Paine says her people were initially reluctant to allow some to leave the country for the San Diego Zoo.
"But when you consider climate change, if anything catastrophic was to happen here... it's sort of like an insurance policy," Paine said.
"In the Maori worldview we believe that everything is connected, so that tuatara are part of our whakapapa—our genealogy," Paine added.
"We are kaitiaki—guardians—of those tuatara, so we have an obligation from our ancestors to ensure their well-being, to make sure they're protected. To lose them would be like losing part of ourselves."
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