The Last of the Wild Things : AFRICAN SILENCES, <i> By Peter Mathiessen (Random House: $21; 225 pp.)</i>

Twenty years ago, Peter Mathiessen observed that of all the African animals the elephant was the most difficult for man to live with, but that its passing--”if this must come”--would be the most tragic of all. At that time, millions of elephants still roamed the bush and the forests of east, central and southern Africa, and the passing of the species seemed unlikely. Today, with its number authoritatively estimated at about 700,000, the African elephant is officially designated a threatened species. To avert the possibility of its extinction, international action was taken last year to outlaw the trade in ivory.

But while that ban has put a virtual stop to the poaching that for so long bloodied the dwindling ranks of Loxodonta Africana (African bush and pygmy elephants), it may not save the creature from extinction. For the biggest threat to the elephant’s survival is not the automatic rifle of the poacher but the panga of the native farmer, whose slash-and-burn techniques destroy the elephant’s habitat.

This seems to be at least implicitly recognized even by the strongest proponents of the ivory ban. Fifteen years ago, Kenya’s elephant population numbered 65,000; today it is fewer than one-third as many. Yet Kenya’s director of wildlife resources, Richard Leakey, who led the successful campaign for an ivory ban, recently conceded that Kenya, with its human population increasing at the rate of almost 4% per annum, can never again support 65,000 elephants, and that “20,000 in some places is too much.”

As Leakey, with a perfectly straight face, recently admitted in Time magazine, “We’re looking at birth control--vaginal rings. I don’t know how they work.” But the stronger likelihood is that Leakey may eventually have to cull Kenya’s elephant herds by rifle fire under political pressure to protect the livelihood of the farmers whose small holdings they damage and destroy.

That kind of paradox is implicit but not directly addressed in “African Silences,” Mathiessen’s latest set of reflections upon the state of the continent’s wildlife. As the author points out, the almost complete absence of wildlife in West Africa is a consequence of human population pressure and the farming techniques that are now consuming vast tracts of East and Central African savannah and forest. In that context, it may prove to be irrelevant whether or not the ban on ivory is renewed at next year’s meeting of the 102-nation Convention on International Trade in Endangered Species.

To the extent that he fails to come to grips with such issues (or to make more than one passing reference to AIDS, the scourge that will wipe out hundreds of thousands of African humans before the end of the century), Mathiessen is not at his justly celebrated best in “African Silences.” Still, it must be said that even on an off day, the author of “The Snow Leopard” and “Killing Mister Watson” is more worth reading than many of his contemporaries at their peak. And although it contains few fresh insights or new information for any reader with even a passing acquaintance with Africa, his “Silences” does include some characteristically fine descriptive passages.

The elephant apart, Mathiessen is particularly good on the even more endangered mountain gorilla, and gives a hilarious account of a confrontation between a band of the latter and a mixed group of white tourists in northeastern Zaire.

“It is a standoff. On one side of this big thicket perhaps 30 large and hairy primates are warning the restless young among them to be quiet, and on the other a like number of large hairless ones are doing the same thing.”

Turning to Homo sapiens, Mathiessen is enchanted by the joyful high spirits of the Pygmy band whom he and some white conservationists accompany on a trek into the vast and unspoiled Ituri Forest. “We’re here in the forest to be happy!” exults a Pygmy elder. “No anger! We’re here to be happy! Anybody who has a bad spirit, keep it in town!” Sadly, the Pygmies’ engaging qualities are not appreciated by their Bantu fellow countrymen, one of whom, a gendarme, confides to Mathiessen and his friends that they have to be “treated like the animals they are.”

The book contains some delicious mysteries. Does an unclassified race of “little people”--not the Pygmies, but some other human strain--hide in the vastness of the Central African rain forest? Rumor, legend and some tantalizing scraps of evidence suggest that, like the Himalayan yeti or the Rocky Mountain bigfoot, such humanoids do exist, but Mathiessen has to concede that the question remains open.

And what about the pygmy elephant, which some naturalists believe to exist as a distinct but elusive animal species? Mathiessen accompanies Dr. David Western of the New York Zoological Society on a search for such a creature, but their conclusion is that the pygmy elephant is really the juvenile version of the forest elephant, which in turn is smaller than the better-known savannah elephant.

Although his emphasis is very much on wildlife, Mathiessen allows himself some passages of reflection on the dashed hopes and sour realities of African independence. In the Ivory Coast, for example, as in many other countries of the new Africa, “a privileged few have acquired enormous wealth. But for the rest things are much the same as they were in the colonial times from which their leaders saved them.”

In the same vein, Mathiessen is particularly, and justifiably, scathing about Zaire’s President-for-Life, Mobutu Sese Seko, who has oppressed and pillaged his people with a zeal and thoroughness that the infamous King Leopold II of the Belgians--founder of the horrendous “Congo Free State”-- might have envied. The corruption and police-state brutalities of the Mobutu regime go hand in hand with a leaden bureaucratic incompetence that has brought a once-thriving economy to the brink of collapse.

Mathiessen is no less censorious of those “inheritors of King Leopold’s bloody legacy” who still live in Zaire and continue to profit from their former colony. Still, as the author observes, while the Belgians also bled Zaire, “at least they knew how to run the country.”