[hinkley]

Elephant matriarchs remember old watering holes that the herd has not visited in decades, and in extreme cases, watering holes that none of the other living members have ever seen.

In drought years these backups may end up getting the herd through the worst of it.

And it turns out that for elephants, water availability is one of the biggest limitations on reproduction. Provide a population with an artificial water source and it will explode in short order.