Up, up, up into the turret we go, David Quammen leading the way. It's a cupola really, a small dome-like structure where he retreats for conversation or meditation, coffee or martinis, atop his cozy stucco and shingle home on an eighth of an acre near downtown Bozeman, Mont. The book-lined room where he writes is on the ground floor, laptop at the ready, a photograph of William Faulkner nearby. Unless traveling to far-flung, wild places, he is there early each day, breaking for breakfast and then disappearing again until late afternoon. Discipline drives him and has made possible, in many of his 10 books to date, lengthy and thoughtful accounts of the complicated forces of the natural world.

Quammen, whose foreboding 1996 nonfiction work from Scribner, The Song of the Dodo: Island Biogeography in an Age of Extinctions, won him great acclaim, cringes at the label of "nature writer." He prefers—cautiously—the more elusive term "landscape writer," since the latter, in his view, incorporates material about the human politics that increasingly impinge on the natural world. His latest volume has the provoking title Monster of God: The Man-Eating Predator in the Jungles of History and the Mind (a starred review in PW) and will be out in September from Norton.

In it, he lays out a warning that is at once philosophical and humorous, passionate and scholarly. Watch out, he laments in some 400 pages with an additional 38 pages of source notes and bibliography: kill off the man-eaters and mankind will suffer the consequences, too. "Great and terrible flesh-eating beasts have always shared landscape with humans," he writes in the introductory chapter. "They were part of the ecological matrix within which Homo sapiens evolved. They were part of the psychological context in which our sense of identity as a species arose. They were part of the spiritual systems that we invented for coping." Doomsday lies ahead. "The foreseeable outcome is that in the year 2150, when human population peaks at around 11 billion, alpha predators will have ceased to exist—except behind chain-link fencing, high-strength glass, and steel bars," he notes. "I think every day about the question of how to persuade people that we should be concerned about tiny species of beetle in the Amazon and parasitic worms in the swamps of Borneo."

This sounds like missionary material, but if he has a mission, he says, it is to entertain—"to beguile as large an audience as possible" in his role as "intermediary between the sciences of ecology and evolutionary biology and the reader who just likes good writing and stories." He doesn't like preaching to the converted. "I want to write for people who don't care beans about the natural world and persuade them somehow." The people, in fact, who would "gag at the thought of nature writing."

How to do so is the tricky part, given his own finely tuned mentality drawn instinctively to subtlety and detailed sourcing. Being a good storyteller saves him, because he certainly doesn't tackle lightweight themes. "Everything I write, whether it is a book or essay or whatever," he says, "is some variant of landscape and how landscape shapes human history."

Connectivity is a constant theme in this and his other writing. His latest book was intended to be what he calls "a sort of palate-cleansing project, after the long complicated effort that went into Dodo," in which he showed how insularity is necessary for new species to develop, but is also a leading factor for extinction. Research into the Asiatic lion in western India led to looking at other large predators and their relations with humans—bears, crocodiles, tigers—resulting in four years of work and travel for Monster, which is also a companion piece to Dodo, he says, "in the sense that it continues my exploration of the interplay among human history, ecological science, and the condition of landscape and biological diversity on earth."

A Cincinnati native, Quammen, 55, recalls being drawn in childhood both to the natural world and to writing. He moved to Montana in 1973 to write and to fish. Montana, of course, is something of a writers' haven—cheaper by far than Manhattan's West Side—as well as a sporting people's playground. His CV, quixotically headlined "tedious but reliable facts about David Quammen," states that he was "educated by Jesuit priests and Southern novelists."

At the top of a list of 11 awards and fellowships is a Rhodes, given him in 1970. He spent his time at Oxford's Merton College doing a thesis on William Faulkner under the supervision of critic and Joyce and Wilde biographer Richard Ellmann, breaking near the end to drop his pencil and head home to campaign for presidential candidate George McGovern in the primaries the day Richard Nixon blockaded Haiphong harbor. He returned later to finish and get a degree. "I went to the wrong Oxford to study—not Oxford, Miss.," he jokes.

Faulkner had a hold on him because of what he calls the Mississippi writer's "obsession with the land," plus "his fascination with questions of epistemology: what people can know and how they can know it; the dark side of human nature and how hard it is to penetrate that with mere knowledge, let alone understanding."

Quammen has a relaxed manner, exhibiting a mix of earnestness, graciousness and sly humor in a tall athletic frame. Outwardly sensitive and even introverted, he eagerly engages in rambunctious outdoor activities such as online skating, skiing, kayaking and ice hockey, declaring a free day whenever a foot of fresh snow falls on city streets. He clearly is proud of choosing an urban tree-lined plot for his base. "I really believe if you love the landscape, live in town and let the elks have the foothills."

Just 24 hours before late morning coffee with PW, he had returned from a two-week honeymoon in Scotland with his second wife, Betsy, a conservation activist. Scotland, like Montana, is great fishing country. The couple hiked instead. A former fishing guide, he admits the temptation was there, but lately he has given up even the catch-release mode. He feels sorry for the fish. Doubtless, few Rhodes scholars turn into fishing guides—which isn't to put down the guide profession, or Oxford, for that matter. Writers often have eclectic backgrounds, but Quammen has unusual credentials that he has put to use in some unusual ways.

For one thing, he has almost no science in his background apart from some graduate courses in zoology. The cliché about a talented writer having a journalist's eye and a novelist's pen is true in his case. He became known to a large reading public as a journalist and essayist while employed by Outside magazine for 14 years, writing the "Natural Acts" column between 1981 and 1995, but he was already a published novelist when he won the Rhodes. And he wrote his early novels—some of them still unpublished—in longhand.

His first novel, To Walk the Line, about blacks and whites on Chicago's West Side, was published in 1970 while he was a senior at Yale studying under Robert Penn Warren, who sent him to his agent. William F. Buckley Jr., mentor of a conservative classmate, read it, liked it and passed the manuscript along to Knopf editor Sophie Wilkins (the translator of Robert Musil and Thomas Mann) whom Quammen remembers with great fondness. She took him under her wing, inviting him down to her New York apartment to go over the manuscript line by line.

Such precociousness didn't necessarily predict an easy run. He paid his dues—13 years elapsed between the first and second book. He tried living in Berkeley, but found that didn't agree. Needing to get away from what he calls "ivy-covered walls," he had begun learning to fly fish on the Tongue River in Wyoming. Remembering the words of a friend who had described Missoula as a beautiful place where "three rivers converge and you can see snow on the mountains in early September," he drove there with $300 in his pocket on September 12, 1973, checked into a rooming house downtown and started another novel while working as a waiter and bartender. Such talents as Thomas McGuane and Bill Hjortsberg had already been attracted to Paradise Valley south of Bozeman. (Montana writers fit no pattern and are a far-flung group by necessity in a state where people often drive 50 miles for dinner.) By coincidence, one of McGuane's sons, a custom knife maker, is the Quammens' neighbor; the muffled sound of a metal lathe can be heard faintly through the windows of the turret.

One of Quammen's first moves in Missoula was to pay a visit to poet Richard Hugo, then the head of creative writing at the University of Montana, to inquire about jobs for writing teachers. "He explained to me in so many words that a Rhodes and a quarter will get you a phone call in Missoula." Bartending was a better option anyway since he could write on the side. He had tried university teaching earlier, at the behest of his Jesuit mentor back in Cincinnati, and realized it was a lot of work that, done well, takes away the energy needed for writing.

If he had as great a biology teacher as he had a Jesuit high school English teacher, he says now, the direction of his life might have been different. He wasn't attracted to nonfiction or realized the possibilities of the essay form until he started reading what he calls "the artful nonfiction" about the natural world by John McPhee, Loren Eiseley and some Stephen Jay Gould, then Edward Abbey—particularly Desert Solitaire—and Annie Dillard's Pilgrim at Tinker Creek; he got to know many of them later as friends. When writer Bill Kittredge read Quammen's short fiction piece about a boy and his father on a disastrous hunting trip—developed out of a novel he had written about the death of Faulkner—things started to click again. The story was printed in TriQuarterly magazine in an issue on Western writers that Kittredge edited. (The story and two other equally long ones were published in paperback form by Graywolf Press in 1988 under the title Blood Line.) Meanwhile, Quammen had quit the bartending racket in frustration and accepted the offer from an entrepreneurial engineer in Butte to help ghostwrite a book on American technology for $1,000 a month. It involved reading a lot about the history of the Manhattan Project and out of it came a spy novel, The Zolta Configuration (Doubleday, 1983). A second spy novel, The Soul of Viktor Tronko, was published by the same house in 1987.

Meanwhile, a New York Times Book Review editor invited him to contribute work, and then came Outside's offer from an editor who had read the TriQuarterly issue. The topic of his first essay for Outside was on what, if anything, are the redeeming merits of mosquitoes. Other magazine commissions followed. The research for a column about the extinction of bird species on Guam led him to the subject of island biogeography, "a subject I didn't even know existed"—which way down the line, with the help of a Guggenheim Fellowship, became Song of the Dodo.

Throughout, his literary agent has been semiretired Los Angeles—based Renee Golden, whom he met through a serendipitous encounter (and a mutual friend) in Montana. Golden took his first spy novel with three chapters and an outline to Doubleday. He has been equally fortunate, he says, in staying through many years and his four latest books with editor Maria Guarnaschelli, originally at Scribner and now at Norton. She bought the idea for Dodo when she was at William Morrow; when she left for Scribner, the house bought it away from Morrow.

Coming next, and way behind deadline, is a book on Charles Darwin and evolution for the new series on scientific discoveries being championed by James Atlas at Norton. He also owes a book to National Geographic Press about the 2,000-mile walk he took two years ago across the Congo Basin. Quammen was accompanied by Mike Fay, an American ecologist and conservationist, in order to write a three-article series for National Geographic. The walk slowed down delivery of Predator by a year since he finds he never can work on more than one book at a time and tries not to divide his working life into units smaller than one week.

Quammen's reading habits show equal care and precision. His morning coffee book of late has been one about Darwin and barnacles—he describes the evolutionist as "a very gentle and admirable fellow." The afternoon cocktail hour has been reserved for Nature's Metropolis by environmental historian William Cronon, about the making of Chicago and—what else?—the interrelationship of the urban and natural world. The choices neatly reflect Quammen's two worlds—mutually dependent and always in motion, if not at war.