Tuatara

New Zealand reptile in climate peril

By Kim Griggs
BBC News Online, Wellington, New Zealand


Just a one degree rise in temperature could spell the end for a "living fossil", New Zealand's tuatara, according to a university researcher.

"One degree makes a difference between all female-producing and all male-producing temperatures," says researcher Nicky Nelson, who completed her doctoral study at Victoria University in December 2001.

"The pivotal temperature is between 21 and 22 degrees Celsius," she told BBC News Online.

The tuatara is the last representative of a reptile species that appeared at the same time as the dinosaurs.

UN estimates

For her research, Ms Nelson artificially incubated 320 tuatara eggs at temperatures of 18, 21, and 22 degrees Celsius. At 21 degrees Celsius, she obtained 96% females. At 22 degrees, she obtained all males. At 18 degrees, the offspring were all female.

"It's a very small temperature change that makes a difference to the sex ratio and that's important because if global warming is a reality, they're talking about temperature changes... up to 5 degrees Celsius," says Ms Nelson.

The United Nations' Intergovernmental Panel on Climate Change (IPCC) estimates that globally averaged surface temperatures will rise between 1.4 and 5.8 degrees Celsius by the end of this century.

Ms Nelson also monitored eggs being incubated in nature during her research and found that they survived in temperatures that ranged from 3 degrees and 34 degrees Celsius. However, the eggs' exposure to the extremes of temperature was brief.

Wild population

Female tuatara mate only about every four years and when they do, they lay their soft-shelled eggs nine months later.

The eggs, which the tuatara bury, take 11 to 16 months to hatch. Tuatara only reach their full size at around 25 to 35 years old, and are estimated to live for between 60 to 100 years.

Tuatara (the spiny back gives the reptile its Maori name) number from 50-60,000, says Peter Gaze, leader of the New Zealand Department of Conservation's Tuatara Recovery Group. "In the last decade, we've really turned the tide. Things are just getting better and better."

Mr Gaze says the eradication of predators from islands where the tuatara already existed and from new island homes are allowing the population to flourish.

Also helping boost the wild population has been the successful incubation of the reptiles at Victoria University (some of the tuatara are showcased at the university in a special enclosure where students bustle past on the way to class).

Quick change

Now, about half of New Zealand's tuatara live on Stephens Island off the top of the South Island of New Zealand and the rest are spread over 35 islands off the coast of New Zealand.

"What I want to work on now is how it actually works in nature," says Ms Nelson.

She wonders if tuatara would respond to any rise in temperature by adapting their nesting habits.

"They've been around since the time of the dinosaurs, so they've been through climate change before and survived, whereas dinosaurs didn't, so they must have some mechanisms for coping with it."

"It's whether they can do it fast enough," she says.

I am sure that this was covered when the article was originally printed in 2002. But found it to be very interesting.

It's interesting, sure, but one would think a "living fossil" to be at least a bit resistant to a 1 degree temp change.

There is a biological, evolutionarily-explained reason for them to have temp. controlled sex ratios. Besides, the animals don't lay their eggs on the surface. They dig. They'll just dig deeper.