“Yes,” he replied. “But not in the way you might think. Certainly, more prey means more to eat. But what has really helped the lions is the increasing forest cover—which is actually because of the wildebeest.”
To understand how the wildebeest affect the trees and thus the lion population, you must know what was here in the past and what is here now. And that is what Sinclair has learned. Over the years, he has studied everything from the population dynamics of the herd animals and their predators to the effect grasshoppers have on the various types of grasslands. He has traveled to almost every corner of the 5,700-square-mile park, counting birds and acacia trees to assess how the various species of trees affect the number and variety of birds and butterflies. He has collected piles of buffalo bones to analyze the fat in their marrow, and he has counted seedlings and shrubs to measure the density of woodland thickets. When he sees a particular species, he jots its name and location in a pocket-size notebook. He also photographs key areas, such as the forests on certain hillsides or bordering major rivers—a record that shows how the tree cover comes and goes. And for the past two decades, he and Mduma have overseen a biodiversity survey of the park, slowly building up a record of its creatures. “None of this is very high tech,” Sinclair said, “but if you keep at it long enough, you begin to see patterns, and then you can pick out changes in those patterns.”
Sinclair has pushed his base line back to the 1850s, using the accounts of explorers, hunters, slave and ivory traders and colonial administrators who ventured here. At that time, and presumably for thousands of years before, the Serengeti ecosystem encompassed some 13,000 square miles. The cattle-herding Maasai people, like the wildebeest, followed the greening of the grasses. To the Maasai, the plains were so vast they said you could walk your entire life and never reach the end. The grasslands were, in their Maa language, siringet: endless plains.
Today about three-quarters of the original habitat is protected in various reserves, the largest being Serengeti National Park with its adjoining game and conservation areas. Much of the rest has been converted into wheat farms, cattle ranches, villages and towns that hem the Serengeti to the north and west, limiting the movement of the animals. The wildebeest face a more direct human threat too. Poachers kill some 20,000 of them each year, both to eat and to sell in bush meat markets. (Sinclair estimates that wildebeest meat feeds about one million people.) But as the human population grows (at a hefty 4 percent annually in the towns along the Serengeti’s western border), the number of poached wildebeest could double or triple. “If that happens, it will be a huge threat to the migration,” said Sinclair. “It’s simply not sustainable.”
For now, though, the migration endures. The animals move from their southern home at the base of Ngorongoro Crater west into the heart of the Serengeti, then north and east across the Mara River into Kenya and its Maasai Mara National Reserve. In November they travel back, completing a clockwise journey through the plains—a distance of some 300 miles.
Did the migration follow this same route before the arrival of the Europeans in the interior of Africa in the mid-1800s?
“We don’t know,” said Sinclair. “I couldn’t get a fix on the size of the herds, or what migration route they followed. What was clear was that the herds collapsed in the early 1900s. There was a horrific die-off. It was a seminal event for the Serengeti, with many long-range consequences. Let me show you what I mean.”
He turned the key in the ignition, and the wildebeest that had been loping past us stopped abruptly to stare. For a few moments we held back the tide of animals. But then, having decided that we were not some deep-throated predator, they bent their heads toward the earth and pushed on. Sinclair drove past the herds, turned up another track, and headed straight north toward a low-slung range of hills. As we bumped through the dust and heat, he told me the story of the disease that changed the Serengeti.
It’s common these days to worry about epidemics from SARS, the Ebola virus or the bird flu coming in from the wild to kill off humankind. But “civilized” diseases can also wreak havoc in the natural world. In the late 1800s, Europeans unintentionally introduced rinderpest, a viral cattle disease, into East Africa. Although the virus was found in European and Asian cows, cattle in Africa had never been exposed to it, and, throughout the continent, they died. Rinderpest also swept through ungulates closely related to cattle, such as the wildebeest and buffalo.
“There were so many dead animals and so much food to scavenge that it was said the vultures forgot to fly,” said Sinclair. He pulled to a stop below a tree-covered hill. “And when the animals—domestic and wild—died, the people died. There was dreadful starvation among the Maasai.”