The Serengeti, a vast grassland along the northern border of Tanzania, is The Last Place where wild animal herds--wildebeest, elephant, lion, zebra, gazelle--gather as in Pleistocene times, and it is this unique configuration that has made it the center of a long controversy about priorities within its borders. Hayes happened upon this conflict several years ago and, in succeeding trips and after numerous interviews, came to value its complexities. Conservationists have fought for animal rights and the preservation of the last large, natural ecosystem--a resource and a tourist draw; the Masai traditionally held grazing and habitation privileges, and depended on them; commercial interests argued for cropping and culling for animal population control; and President Nyerere, caught up in these claims and political/economic imperatives, favored a modification of socialism to rural African traditions and local (Ujamaa--family) settlements. Moreover, until recently the articulate, powerful exponents of each point of view were white ""expatriates"" who knew they would--and should--be replaced by Tanzanians. Hayes sorts this all out slowly, comparing the expatriates to ""members of a large, talented, difficult family. . . self-absorbed, quarreling. . . and driven nearly to distraction over how to save the property."" He concludes, as the Tanzanians did, that the Serengeti is a unique resource, an irreplaceable national asset to be accommodated and preserved. Hayes repeats himself occasionally but meanders purposefully--he accompanies Grzimek, the most zealous conservationist, to Uganda--and he encourages the expatriates to talk about each other. What emerges are a clear sense of the problem (a section appeared in The New Yorker) and finely etched views of the principals.