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It has survived ice ages, volcanic eruptions and the intrusion of humans on its South Pacific island home, but New Zealand's last survivor of the dinosaur age may become extinct because of global warming.
Mounted with spiny scales from head to tail and covered with rough, grey skin
that disguises it among the trees, the tuatara is one of the world's oldest living creatures.
But the lizard-like reptile is facing increasing risk of extinction from global warming because of its dependence on the temperature which determines the sex of unborn young.
"They've certainly survived the climate changes in the past but most of them [past climate changes] have been at a slower rate," said Jennifer Moore, a Victoria University researcher investigating the tuatara's sexual behaviour.
"So you wouldn't expect these guys to be able to adapt to a climate that's changing so rapidly."
The sex of a tuatara depends on the temperature of the soil where the eggs are laid. A cooler temperature produces females and a warmer soil temperature results in male offspring.
The tuatara is the only survivor of its species of reptile that flourished during the age of the dinosaurs, some 200 million years ago.
It can grow up to 50cm and weigh up to 1kg and like its reptile relative, the turtle, the slow-moving tuatara can live more than 100 years, feeding mainly on insects.
But scientists say its long life span as well as its four-year breeding cycle - relatively slow for a reptile - will make the adaptation process more difficult.
Already male tuatara on Stephens Island, a tiny predator-free island in the Marlborough Sounds, outnumber females by 1.7 times, said Ms Moore.
Much of New Zealand's unique wildlife has come under threat since the arrival of humans.
Some indigenous species, such as the giant moa, became extinct because of overhunting and the introduction of predators, such as rats, dogs and weasels.
But New Zealand is known as a leader in wildlife conservation, saving the likes of the Chatham Islands black robin from extinction. In 1980 there were just five black robins, now there are about 250.
Peter Gaze, a senior conservation officer at the Department of Conservation, says global warming has become a new challenge for many of New Zealand's wildlife.
"I think the impact of temperature change is widespread and diverse," he said.
Rare species such as the rock wren - ancient, tailless birds found only in the South Island mountain ranges - could become extinct if the warmer climate allows predators such as rats to live at higher altitudes.
The United Nations Intergovernmental Panel on Climate Change, the world's top authority on global warming, predicted in a report in February that global temperatures would rise by 1.8C to 4C this century.
It also warned that between 20 to 30 per cent of plant and animal species face an increased risk of extinction if the rise in the average global temperature exceeds 1.5 to 2.5C.
The tuatara, once found throughout New Zealand, is now limited to around 30 isolated islands.
Alarmed by the rapid decrease, New Zealand has put it on its endangered species list and has bolstered its numbers through artificial breeding and returning them to uninhabited islands cleared of predators.
Scientists say the tuatara population has recovered to around 50,000 to 60,000, but the little dinosaurs may find themselves giving birth only in laboratories if temperatures keep climbing.
"The easiest way for the tuatara to survive would be for nesting female tuatara to change their behaviour and modify the areas where they nest, such as laying eggs deeper in the soil," Ms Moore said.
"There is a possibility they will be able to adapt but I think the problem is that temperatures may rise so quickly they won't have time."
- REUTERS
