But that's not the whole story. Foley, a graduate student in Ecology and Evolutionary Biology now doing field work in Tanzania's Tarangire National Park, studies the long-term effects of poaching on elephant society.
Male elephants leave the family group early and return to the female groups only to breed.
The matriarch makes decisions for the group about where to go to get food and water and how long to stay there. The old females are a repository for information about habitat. They remember, for example, where they can go to find water during a drought. What poachers want is the biggest tusks, Foley points out. By the time they get down to males in their 20s, the tusks aren't much bigger than the older females, so the poachers start targeting the oldest females.