[TONY:] When I first arrived, there were a few other scientists there. And they had established some form of ballpark figure for the number of animals. [airplane engine noise] [NARRATOR:] The first aerial survey of the park tallied an incredible total of almost 400,000 large mammals.
And curiously, the numbers of certain species were increasing dramatically. [TONY:] The very first surveys of the buffalo in 1961 counted about 15,000 animals in the park. The next time they did that in 1965, they counted 35,000.
For a large mammal, they just don't do that sort of thing! [TONY (from footage):] The idea is to follow the herd around. .
. [TONY:] And so I became involved in counting the buffalo from that moment on, year after year, which required doing a lot of flying. Once a year, we had to fly across the whole of the Serengeti and count every single animal that we saw.
[music plays] Of course these herds are quite big, so we had to take photographs, and then I counted the animals off the photographs. [music plays] [NARRATOR:] Tony's counts revealed that buffalo weren't the only ones increasing. Wildebeest populations were skyrocketing too.
Tony's PhD project was to figure out why. [music plays] He learned that a virus called rinderpest had killed 95% of East Africa's cattle when it first arrived in 1890, and it had periodically decimated Africa's cattle populations ever since. [TONY:] It turns out that wild animals that were closely related to cattle, like buffalo and wildebeest, they also suffer from this disease.
[NARRATOR:] Tony discovered that a new vaccine to eradicate rinderpest from cattle had also eliminated the virus from the Serengeti's wildlife. The disappearance of rinderpest precisely matched the time when buffalo and wildebeest populations began to explode. This boom was an opportunity for Tony to learn what regulates these animals' numbers, and the entire Serengeti ecosystem.
