When an old African elephant matriarch hears a lion roar out on the savanna, she listens to discern whether it's a male or female. Why does she care? Because male lions are more likely to attack. (See: "Older Elephants Know the Best Anti-Lion Moves.")

Not many predators can take down an elephant, so it's useful for the massive mammals to know when it's worth their effort to run away. "We know that African elephants have very sophisticated discrimination abilities," says Lucy Bates, a research fellow at the University of St. Andrews in the U.K. They also respond to the buzz of disturbed African honeybees, and can smell the difference between human friends and foes.

Conservationists hope to use