Some years ago, South Africa's game managers had to figure out what to do about the elephant herd at Kruger National Park. The herd was growing well beyond the ability of the park to sustain it. And so they decided to transport some of the herd to a nearby game park. 

A dozen years later, however, several of the young male elephants (now teenagers) that had been transported to the game park began attacking the park's herd of white rhinos, an endangered species. They used their trunks to throw sticks at …