Tuesday, November 14, 2006

Hot Times For Male Tuataras

Less than one degree Celsius is all that stands between the tuatara—New Zealand's "living fossil" reptile—and extinction, scientists say.

From National Geographic News:

The sex of tuatara—the sole surviving species of an ancient family of reptiles dating back 200 million years—is determined by the incubation temperature of its eggs. As the mercury climbs, so does the proportion of male hatchlings.

The mechanism is so delicate that a flagging population on remote North Brother Island in Cook Strait is already running short of breeding females. Nicky Nelson, a senior lecturer at Victoria University in Wellington, New Zealand, says experiments show that 21.7 degrees could be the pivotal temperature.

"At 22 degrees Celsius, we got 100 percent males. At 21 degrees Celsius, we got three males out of 80 eggs," Nelson said.

Intensifying the problem is the slow reproduction rate of the reptiles. On average, female tuatara mate once every four years, and eggs take between 11 and 16 months to hatch.

Tuatara have endured climatic chaos before, Nelson says—they even survived the meteor strike many believe wiped out the dinosaurs. But the reptiles were far more abundant back then, bestowing them with enough genetic diversity to see them through the global catastrophe, Nelson says. Now, with their numbers already decimated [decimate actually means to decrease by 10%--PBlog], the species may face a much faster rate of warming.

So scientists are gathering eggs and raising them in artificial incubators.
"We can dial in whichever sex we like," Nelson said.

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.