THE TIMES (London, UK) 02 July 08 After 200 million years, all-male future spells doom for reptiles - Global warming means that all tuataras may end up being born male (Lewis Smith)
The only survivors in the wild of an order of reptiles that scampered with dinosaurs could be wiped out because climate change will turn them all into males.
The gender of tuataras, an ancient type of reptile with three eyes, is determined by the temperatures that the embryos are kept at when in the egg. Global warming means that the reptiles, regarded as living fossils, face the threat of dying out in the wild because of a terminal shortage of females.
Only males will be born in nests where the eggs have been kept at temperatures of 22.25C (72.05F) whereas females are guaranteed only at temperatures lower than 22.1C.
Modelling showing the likely impact of climate change on the last remaining homes of tuataras showed that the last female could hatch by 2085 for at least one of the two surviving species.
Tuataras evolved 225 million years ago. The two remaining species cling on to survival in New Zealand and are regarded as among the oddest reptiles. They have a mysterious third eye at the top of their heads, are able to hold their breath for an hour and, despite their cold-blooded nature, are nocturnal.
Until rats and other mammals - introduced by humans - arrived, the reptiles were widespread in New Zealand but they are now found only on a handful of small islands safe from the mainland.
With climate change, average temperatures are expected to rise by up to 4C (7.2F) by 2085, which would be enough to ensure that all the North Brother Island tuataras, Sphenodon guntheri, are hatched male. The other species, the Cook Strait tuatara, S. punctatus, could follow soon afterwards.
The reptiles have coped with climate change in the past but their range is now so limited, being restricted to a few islands, that they are unable to migrate to cooler areas to protect themselves.
Learning to lay eggs in shadier areas or later in the season when the worst of the heat is over are adaptations that would help them to overcome the threat of extinction. Researchers, however, think it unlikely that the animals will change their behaviour.
The findings are published in the journal Proceedings of the Royal SocietyB. Researchers suggest that the tuataras could be saved in their natural habitat if conservationists provided nest sites with artificial shade once the embryos have started to develop.
“Tuatara are ancient animals. Their ancestors were scurrying around the feet of dinosaurs. It would be a great shame to lose them,” Michael Kearney, of the University of Melbourne, said.
Both surviving species of tuatara are from the sphenodontian family that first appeared more than 200 million years ago. They come in several colours, which often change during their lifetime. They can grow more than 2ft (60cm) and can live for more than 100 years.
Tuataras are distinct from lizards. The differences between them include the lack of a penis in the male tuatara. Along their backs they have a crest of spiky scales. The name tuatara comes from a Maori word that means “peaks on back”. The third eye is covered by scales and pigment and its use is unknown, though scientists suspect that it helps the animals to tell the time.
Tuataras live in burrows, often sharing with birds - and eating occasional chicks. They emerge at night to catch any small animal that comes close enough to bite. Worms, wetas (insects) and millipedes form the bulk of the tuatara's diet.
http://www.timesonline.co.uk/tol/news/environment/article4251775.ece
THE AGE (Melbourne, Australia) 03 July 08 All boys and no girls mean tuatara's future is a short one
Chee Chee Leung)
A Three-Eyed reptile whose ancestors used to scurry under the feet of dinosaurs could die out as global warming turns them all into males.
The sex of tuatara, which look like giant, greenish-brown lizards, depends on the temperature of their nest. When it is above 22 degrees, only males are born, while females are produced at temperatures of about 21 degrees.
Work modelling the impact of climate change on tuatara homes — which face potential warming of up to 4 degrees by the 2080s — shows that males from at least one of the last two remaining species could be doomed to a single-sex life within 80 years, guaranteeing their extinction.
The researchers, from Australia and New Zealand, say human intervention is needed to help these so-called "living fossils", the only survivors of the ancient Sphenodontia reptile family that evolved more than 200 million years ago.
"They are the last representatives of their group and a really important part of the Earth's biological heritage," said University of Melbourne zoologist Dr Michael Kearney. "It would be very sad to lose them."
Tuatara means "spiny back" in Maori. They are distantly related to snakes and lizards, and considered unusual reptiles, as they are nocturnal and do not like the heat.
The animals, which grow to about 80 centimetres long, are only found on New Zealand's offshore islands. The introduction of mammals by humans wiped them out on the mainland. They are thought to live for as long as 100 years.
The remaining 34 populations range in size from 10 to 30,000 animals, some on rocks of just half a hectare.
Researchers say their ability to adapt to warmer temperatures is low, and that moving the animals to cooler climes — or constructing shaded areas around their nests — will provide them with the best chance for survival. The study is published in this week's edition of Proceedings of the Royal Society.
Other animals whose gender is determined by temperature during early development include crocodiles and turtles.
http://www.theage.com.au/national/all-boys-and-no-girls-mean-tuataras-future-is-a-short-one-20080702-30ot.html
