George Schaller, whose "The Serengeti Lion" won the National Book Award, is almost as hard to classify as some of the rare, exotic animals he makes such extraordinary efforts to study: Scholar, conservationist, poet, adventurer, philosopher; he is all of these and when he goes trekking in the mountains of Asia or the plains or Seregeti he constitutes, by himself, an expedition.

Usually, in the liner medium of print, he fills these roles one at a time, but sometimes they coalesce, and then his book is at its best. For exmple, when he is admiring the mountain-climbing virtuosity of the tahr (an evolutionary link between goat and antelope) in the Himalayas:

"They balanced readily along ledges only a few inches wide, and at times would leap with precision onto small tussocks growing on a sheer cliff a few feet below. Tahr are well adapted to such rocky realms. Their hoof pads are soft and surrounded by a horny rim, providing good traction. When confronted with a sloping cliff, a tahr may rock back and forth, then suddenly propel itself upward with a series of leaps, using its broad, furry chest pad and the callus on each knee instead of hooves to fleetingly grip the surface. These animals also have on another advantage over man -- they lack fear."

Schaller, who is director of conservation for the New York Zoological Society, was not in the mountains to write poetry about goats or work out his definition of fear ("an anticipation of future feelings based on past events"), but to observe the mating ritual of the tahr. "My days in the field were long," he reports, "five hours of hiking to and from tahr cliffs plus indeterminable hours of chilly waiting for tahr to appear or do something besides eat and sleep." But the trouble was rapid; one rather revolting detail of mating behavior showed the tahr acting more like goats than antelopes and thus added to scientific knowledge.

This rather obscure species of mountain goat is only a small part of Schaller's interests in his account of several expeditions to various parts of the Himalayas throughout their whole length, "From Afghanistan in the west to China in the southeast. . . one gigantic arc for nearly 2,000 miles . . . a frozen barrier between the Indian subcontinent and the Tibetan plateau." He went there repeatedly on one trip by Peter Matthiessen, who wrote "The Snow Leopard" about it) "to study the world's greatest variety of sheep and goats," to find "areas tht would make good national parks or reserves," buy above all he was drawn by "the snow leopard, a rare and elusive creature which lured me on, only seldom permitting a glimpse."

One of his encounters with a snow leopard, only 150 feet away, is described early in the book: "Her smoky-gray coat sprinkled with black rosettes perfectly complemented the rocks and snowy wastes, and her pale eyes conveyed an image of immense solitude. As we watched each other the clouds descended once more, entombing us and bringing more snow. Perhaps sensing that I meant her no harm, she sat up. Though snow soon capped her head and shoulders, she remained silent and still, seemingly impervious to the elements." In a long moment of mutual attention, he reached the rare state of contemplation where one "almost seems to become what one beholds."

But such mystic moments are rare. Much of the book deals with arduous climbing, landscapes succumbing to human waste and carelessness even in the most remote and inaccessible parts of the world, villagers who lie, cheat and steal, porters who turn back with their work half-done, and weather as harsh as that of Siberia. The instants of exaltation are rare, brief, and hardwon; some of the herds that Schaller stalks grow smaller each year, and he knows that some of the species he studies are near extinction. Still, he travels and writes, partly in the hope of saving a few species with his pen.

The naturalist's work takes him from the sublime to the mundane, from mystic union with a predator to the analysis of its droppings; by learning what a leopard or a wolf has eaten, the scientist can detrmine what other species live in the area. On his final visit to Nepal, Schaller spends five weeks searching for the snow leopard and is rewarded only with one momentary glimpse of a leopard bounding away on his last day in the field. No matter; the leopard has left evidence behind. Schaller tracks it down, he reports, and then, "Full of delight, as if on a treasure hunt, I hurry along the trail collecting feces, old and fresh, and taking notes."

Despite his ability to delight in what could give joy only to a pure scientist (or perhaps a pure poet), Schaller makes his book as much an elegy as a celebration, filled with "lonely thoughts born of windswept mountain passes."

But a large part of the problem is that the mountains are not lonely enough. Again and again, he sounds variations on the same wrning: "Although Nepal's midlands wre once covered with forests, over half of the land has been cleared in the past 20 years to provide more space to grow food and to produce lumber. . . Once man has destroyed what the mountains have offered, the forest and the soil, there is no reprieve."