Ecoscience: The Serengeti: A Natural Ecosystem

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Part II

Paul Ehrlich (Bing Professor of Population Studies and Professor of Biological Sciences, Stanford University) and Anne Ehrlich (Senior Research Associate, Department of Biological Sciences, Stanford) are familiar names to ecologists and environmentalists everywhere. But while most folks are aware of the Ehrlichs' popular writing in the areas of ecology and overpopulation (most of us—for instance—have read Paul's book The Population Bomb), few people have any idea of how deeply the Ehrlichs are involved in ecological research (the type that tends to be published only in technical journals and college texts). That's why we're pleased to present this regular semitechnical column by these wellknown authors/ ecologists/educators.

by Anne and Paul Ehrlich

In our last column we discussed how the large herbivores in the Serengeti ecosystem divide their food resources. Such resource partitioning is not restricted to the herbivores, though: The predators that feed on those herbivores do it, too.

Lions (which weigh 200 to 400 pounds) feed primarily on zebras and wildebeests when those migrating herbivores are within their prides' territories, which can be found in both the plains and the woodlands. The cats' prey among nonmigratory ungulates includes buffalo (which no other predator can kill) and giraffes, as well as warthogs and antelope. Lions stalk their prey mostly at night and sprint to catch their meals. Sometimes they hunt alone, sometimes in small groups.

Another large cat of the Serengeti, the leopard (75 to 130 pounds), is confined to the woodlands and generally takes smaller quarry than the lion does. At the uppermost end of the size scale, the leopard's choice of prey (Thomson's gazelles, topi, and an occasional zebra) overlaps that of the lion, but the spotted cat feeds extensively on smaller antelope such as Kirk's dik-dik (only 15" high at the shoulder), small carnivores, hares, and birds. The leopard is a solitary, nocturnal, stalk-and-sprint predator.

The cheetah is as large and heavy as the leopard, but is much more slender. It hunts in the daytime, taking small antelope and hares. After stalking, it can run down its prey at speeds up to 60 mph. This cat, the classic longdistance sprint predator, may chase its quarry as far as 350 yards, whereas a lion will sprint no more than 50.

Hyenas hunt the plains at night and in the early hours of the morning—in groups of one to three for wildebeests and other antelope, and in packs of four to twenty for the larger zebras. They are pursuit predators; that is, they may harry their prey for up to two miles before finally making the kill.

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