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 elephants' keen senses to reduce conflicts that arise when elephants munch on humans' crops. Until now, researchers have focused on African elephants, but the first study with Asian elephants shows them to be equally adept at sensing threats.
So, what's new? A study published in Biology Letters today suggests that wild Asian elephants (Elephas maximus) can tell the growls of various big cats apart and know which pose more danger to them.
Co-author Vivek Thuppil, an animal behaviorist at the University of California, Davis, heard about a farmer in southern India who played a recording of a tiger growl to scare elephants off his property. Thuppil and his colleagues wanted to test the strategy. Using video cameras camouflaged with elephant dung, they documented Asian elephants' reactions to pre-recorded tiger and leopard growls along village farm roads in southern India at night—prime raiding time.
When the elephants heard the tiger growls, they crept silently away. Leopard growls elicited a very different reaction—stomping, circling, and trumpet calls—although the elephants did eventually retreat. "You don't want to get involved with anything that has claws and teeth," says Thuppil. "So, they eventually decided to choose the safe option, which was interesting."
Watch elephants run from a leopard growl.
What does this mean? A leopard probably couldn't do much damage to an elephant, while tigers sometimes eat elephant calves and could seriously injure adults. "It would pay for the elephants to recognize when a tiger is nearby so they can retreat, without wasting time by running away for every big-cat growl they hear," says Bates, who was not affiliated with the study.
Unique guttural pulse patterns in each animal's growl may help Asian elephants differentiate between the two feline species. Elephants growl too, and have evolved to recognize growls from different individuals in their herd based on small acoustic differences. That capacity might translate to helping them distinguish between tiger and leopard growls, says Thuppil.
Why is this important? In India, more than 200 people die in elephant attacks annually, while humans kill at least that many elephants each year. Since deaths on both sides are often related to crop raiding, new methods of keeping the peace between humans and elephants are in high demand.
"This study adds to our growing knowledge of how elephants perceive the world, and it is exciting because it could have implications for the struggle to reduce human-elephant conflict," says Bates.
What's next? Broadcasting tiger growls over speakers could be an easy way to trick elephants into steering clear of Indian villages. But that conservation strategy might stop working if elephants get used to hearing the sounds. "Something like this would need to be more fine-tuned," says Thuppil. One way to do that is to simulate a moving threat by playing a sound in different places; that's the UC Davis team's next research project.