Digging for What, Exactly?

While the rest of the herd wandered on, one elephant hung back, going at the ground like it had personally offended her. The people watching were totally stumped. What was this determined female elephant trying to do? Was she hunting for something valuable buried below? Elephants are famous for digging, especially when they’re trying to uncover hidden water.
With a little effort, they can pull up as much as two gallons, using their trunks to drink and soak up important minerals from the groundwater. But this didn’t look like a normal water run. The hours dragged on and she kept digging, and everyone just stood there, baffled. What could possibly matter so much that she wouldn’t follow her herd? With every fresh scoop of dirt, the mystery only got bigger.