The world's oldest surviving reptiles, turtles are also ecologically invaluable critters. That's why the English-born Pritchard's work to save them from extinction — and soup — is as serious as it is offbeat. Like alligators and other large burrowing animals, turtles are "eco-system architects," says Pritchard. "A turtle's burrow has got an incredible variety of things living in it."

Pritchard has done his most important and innovative work along the Atlantic coast in Guyana, the South American country that is home to four of the world's eight known sea turtle species: the leatherback, green, hawksbill and the olive ridley. By the 1960s, overhunting by local Arawak Indians — themselves an endangered group — had ravaged the turtle population. But Pritchard helped save both turtles and tribe: He has lobbied Guyana and private sources for grants that have weaned the Arawaks off turtle meat and into chicken farming. And he hires Arawaks at his study camp to tag turtles for research and to police nesting grounds against poachers. The killing has largely stopped, he says, because turtle protection is now "a family discipline thing" among Arawaks "rather than an outsider laying down the law." Along the way, Pritchard's own scholarship has benefitted from centuries' worth of tribal turtle knowledge.

It wasn't the turtles' "slight smiles" that first attracted Pritchard. Because his Australian father was an anatomy professor in Belfast, Pritchard grew up fascinated by bones — and found that few animals have a more elegantly designed skeleton than a turtle. Around his Oviedo home and the nearby Chelonia institute (Chelonia is Latin for tortoise, a land turtle), he likes to show off skeletons from 264 of the 290 known turtle species, which complement his collection of preserved turtle specimens, considered the world's best. Among them is the skeleton of a rare Lonesome George tortoise he found in the Galapagos Islands in 1972.

Unabashedly old-fashioned, Pritchard eschews the Internet and even has an assistant read his e-mail. Some colleagues frown on his unacademic pursuits; but they concede that Pritchard, author of the Encyclopedia of Turtles, is perhaps the world's foremost expert. He has helped point out, for example, that female turtles make many nests, meaning that killing even a few can have geometric consequences: "In Florida, we get 20 or 30 leatherback nests a year," he says. "But those nests might be laid by only two or three turtles." Says Russell Mittermeier, president of Conservation International in Washington, D.C., "Peter's an icon — a link between the hard-core turtle scientists and the conservationist community."

Pritchard's conservation goals today include coming up with the first reliable count of the number of female sea turtles still alive in the world. And then, of course, there's the unusual. The Guyana government is negotiating with a Frisco, Texas firm to build a commercial space port to launch communications satellites near Pritchard's primitive Arawak camp. He, in turn, is urging the company to show its good intentions toward the local ecosytem by creating a wildlife sanctuary beside the launching pad. That might widen the turtles' smiles.