Wed October 17, 2012
Tough Old Lizard To Face Grave Romantic Troubles, Say Scientists
Originally published on Wed October 17, 2012 10:44 am
First off, this lizard? It's not really a lizard. It's an almost vanished species, a reptile like no other.
Its nearest relatives are ichthyosaurs, pterosaurs, animals that lived during the Mesozoic, before the great dinosaurs. They're all extinct now. This is the only one (of the order Sphenodontia) to make it through the meteorite that crashed to Earth and wiped out the big guys, through ice ages, volcanoes, changes in sea levels, through rat invasions, human invasions, pig invasions. And now, after 230 million years hunting insects in the forest, having lasted this long, this little guy is, oddly, in trouble.
New Zealand biologists worry that soon, these animals may not be able to produce females. Male babies will keep coming. But without females, they can't produce offspring. And thereby hangs a tale.
They are called tuataras, a New Zealand-Maori word for "spiny back." In daytime, they're not the liveliest of animals. When biologist Richard Fortey spotted one, it didn't run away. "In fact," as he watched, "it did not do anything at all for a very long time." So he waited. "I am hoping it would at least lift a leg or something to indicate that it is alive. Instead it just sits there, enduring through geological time."
They're not in a rush. Tuataras can live for a hundred years or more. It takes them 10 to 20 years to reach sexual maturity. When it's time to mate, the male darkens its skin, raises its spiny crests and does a little circle dance around the female with stiffened legs. It has no penis. It rubs where it needs to, if the female allows. A male named "Henry," now resident at the Southland Museum in Invercargill, New Zealand, fathered his first 11 babies at the age of 111. His mate, "Mildred," is in her 70s. When they age, it shows mostly in their teeth, which get dull. That's when they switch to softer foods like worms and slugs.
Tuataras quicken when the sun goes down. They are night hunters, looking for crickets, beetles and, sometimes, each other. Like most reptiles, tuataras are ectothermic. "They can hide in the shade, bask in the sunshine, but they can't generate their own heat," says Harvard entomologist Piotr Naskrecki, who's been crazy for tuataras since he was a boy in Poland. (He remembers that Poland's oldest university in Krakow got one, advertising it as "the closest thing to a living dinosaur the human race would ever have a chance to see." It had a handsome cage. "It was probably the only inhabitant of 1960s communist Poland whose quarters were air-conditioned," he says. "I envisioned a gargantuan monster, perhaps a real-life dragon." But it didn't survive.)
Naskrecki says the special thing about tuataras is they don't need very warm weather to become active. Tuataras' "optimal body temperature is 16 to 21 degrees centigrade, the lowest of any reptile," he writes in his new book. They can stay active all the way down to 7 degrees [what we Fahrenheiters call 44 degrees, brrrrr], which is how they compete. When modern lizards go quiet at night, tuataras are still up and about. They can forage for food, but they can't fight off rats or dogs, so they no longer live on the mainland in New Zealand. They've retreated to little offshore islands, where they are protected by the government, but here's the problem.
It's getting warmer.
Tuataras are very temperature sensitive when it comes to gender. The sex of a hatchling depends on the temperature of the egg. Over 72 degrees (22 C), they are more likely to become males. Under 72, they swing female. The swings are steep, ratios of 80-20, but at the extreme, when it's 64 degrees cool, all hatchlings will be female. When it warms up enough, all hatchlings are males.
If they could spread out, climb to higher elevations, move to warmer spots, they could handle climate change, but these lizards are now locked into very small spaces — "small pimple[s] of land," says Richard Fortey — and they can't adjust. That's why biologists at Victoria University now worry out loud about their future. A climatic model for one of the northern (warmer) islands suggests that by 2085, no females will be able to develop. That's why this week, 222 tuataras were flown down to the colder parts of New Zealand in hopes that one day, they will gestate females. Left to themselves, they may begin to disappear.
"This would be more than unjust," says Richard Fortey. These animals have been around so long, survived so much, that losing them "would be an insult to the virtues of endurance."
Fortey, in a new book, imagines a future scenario, not that far off, where hiding in the thick forest are these fierce, territorial, 100-year-old males, stalking their territories, defending against the other males, waiting for a lady to happen by. They sit there, listening with their primitive ears, their spiny crests tense, waiting ... waiting ... waiting ...
Here's a video of young tuataras being released in a highly protected "ecosanctuary" this week. They're adorable, in a lizardy sort of way. Harvard entomologist Piotr Naskrecki took all the photos for this post; they appear in his new book: "Relics: Travels in Nature's Time Machine," a ravishing collection that describes plants and animals that have hung around the planet for a long, long time, defying the odds. These are our true survivors. Tuataras are there, of course, along with beetles and ferns, cycads, horseshoe crabs, all photographed by Piotr, whose masterful eye is on regular display at his blog (one of my favorites) The Smaller Majority. The science paper about warming and tuataras can be found here. Those same horseshoe crabs (and the tuataras) appear in Richard Fortey's book "Horseshoe Crabs and Velvet Worms: The Story of the Animals and Plants That Time Has Left Behind." Fortey, one of our great living biologists, an expert on trilobites (may they rest in peace), is also celebrating creatures that have a knack for continuing. Both authors try to keep smiling, but it's hard.