Return of the tuatara: a relict from the age of dinosaurs gets a human assist - reptile conservation effort - Cover Story

Science News,  Nov 8, 1997  by Christine Mlot

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They're cold, they're old, they're slow. Tuatara, spiny cousins of lizards, are among the coldest of the cold-blooded reptiles, living on brisk, wind-whipped islands off the mainland of New Zealand. They take years to develop and hatch but then make the most of that effort. Growing to almost 2 feet long, tuatara live at least the biblical threescore and ten years, and probably a century or more.

Tuatara are also a zoological rarity, the lone members of the order Sphenodontida. The rest of the order probably went extinct with the dinosaurs, leaving only the tuatara to carry on. Their Maori name means "spiny back"; it could easily stand for "staying power."

Tuatara are now gaining some new ground. In the last decade, researchers in New Zealand studying the animal's unusual reproduction set up an incubation program for eggs collected from the wild. Two years ago this month, a cohort of the nursery-hatched tuatara was sent to recolonize an island that the animals once inhabited.

Although it will be years before known whether the colonists have established a lasting population, the tuatara seem to be thriving. "The indications so far are very good," says zoologist Charles H. Daugherty of Victoria University of Wellington in New Zealand.

The repopulation experiment is one small step for tuatara, one giant leap for Reptilia. Many reptiles today are threatened with extinction--21 species have gone the way of the dinosaurs in the last 400 years--but they attract little of the public concern bestowed on furry or feathered animals.

While restorations of bird and mammal populations are relatively common, efforts to conserve reptiles have tagged. The attempt to reestablish tuatara may provide insights into restocking other reptile populations on islands or in other ecosystems where they've been eliminated, says Daugherty, who described the project at last summer's meeting of the Society for Conservation Biology in Victoria, British Columbia.

There's a certain symmetry in the human-assisted return of the tuatara, since mammals probably played a part in their near demise. Tuatara and other sphenodontids were once more common than lizards and were found all over the world.

They had their heyday, along with dinosaurs and other reptiles, beginning about 220 million years ago. By the time the Mesozoic era was winding down, about 65 million years ago, only four groups of the once-dominant reptiles survived: snakes and lizards, the most diverse with thousands of species; turtles and tortoises, with a couple hundred species; about 2 dozen alligator and crocodile species; and tuatara.

Their abundance in the fossil record stops short just before mammals began to flourish. Explains Daugherty, "When the dinosaurs went extinct, it appears that most of the sphenodontids did as well. There are no fossils more recent than 80 million years ago anywhere. But because apparently there were a few tuatara that gained safety on this little raft of New Zealand, they hung on."

When New Zealand rafted away from the other landmasses about 80 million years ago, it carried no mammals that threatened tuatara. So the reptiles persisted unperturbed, adapting to the cool, seaside habitat with little physical change from their dinosaur-era ancestors.

About 1,000 years ago, Polynesians arrived in New Zealand, bringing with them rats and dogs, which took to preying on tuatara. The tuatara populations dwindled further with the arrival of Europeans, including collectors avid for the reptilian throwback. By the middle of the last century, tuatara were extinct on the New Zealand mainland.

Only on the roughest, most inaccessible islets have tuatara survived, about 55,000 in all. Tuatara, have been protected since 1895--one of the first reptiles to obtain that legal status. Still, 10 of the 40 populations reported at the time have disappeared in the past century, and four more are on the brink.

Tuatara share their island sanctuaries with flocks of shearwaters and petrels. The reptiles spend their days in burrows left by the nesting seabirds, thus avoiding the hawks that fly by the island as well. At night, the tuatara come out to feed on the abundant beetles and other creatures that live amid the scrub.

Life is laid-back, even when these reptiles hunt. "Tuatara are sit-and-wait predators," says Daugherty "They sit in front of their burrow all night, in a sort of advertising display [to ward off] other tuatara, and hoping a food item will wander by" They aren't fussy about what they eat: skinks, worms, giant weta crickets, even young tuatara or birds--anything that moves.

Their sangfroid suits the island's average 50 [degrees] F temperature, which can plunge nearly to freezing. Researchers consider tuatara to be an extraordinarily modified version of the basic heat-seeking reptile. "If you take them up to the normal temperature for most reptiles, they'll die," says herpetologist Louis J. Guillette Jr. of the University of Florida in Gainesville.