Hungry Elephants Are No Match for Fearless Ants

Talk about your David and Goliath story: ant colonies have found a way to ward elephants away from their turf with painful, precise attacks.

African farmers have an unusually large and bulky pest problem: elephants. These enormous creatures trample over fences, ignore loud noise-deterrents, and nonchalantly feast on a wide array of crops, from tomatoes to potatoes.

But where humans, fences, and noise have failed ants might be able to save the day, according to a new study.

Researchers Todd Palmer at the University of Florida and Jacob Goheen at the University of Wyoming observed the eating patterns of elephants on Kenyan savannas and stumbled upon an incredible anomaly: the lumbering mammals plowed through everything that they encountered, save for one type of tree (Acacia drepanolobium) that was covered in ants.

To determine whether it was the tree or the ants that was driving the pachyderms away, Palmer and Goheen set up a series of "cafeteria trials." The researchers offered elephants four branches: two branches from the enigmatic "ant-plant" - one with ants and one without - and two branches from the elephant's favorite tree (Acacia mellifera), again one with ants and one without.

"We found that the elephants like to eat the ant-plants just as much as they like to eat their favorite tree species, and that when either tree species had ants on them, the elephants avoided those trees like a kid avoids broccoli," Palmer explained to Discovery News.

So, why the strong aversion to ants? Turns out elephants are not the tough guys their heft and tusks would have us think they are.

Though elephants sport resilient, leathery exteriors, the skin on the inside of the animals' trunks is extremely sensitive and tender. When an elephant grabs a branch from an ant-filled tree, the colony attacks. Tiny warriors swarm into the elephant's trunk and bite the brute the where it hurts.

All it takes is one sniff of the ants to send a herd running. By going for the elephants' "achilles heel," these ants have effectively warded off the nefarious super-eaters from damaging entire savanna ecosystems.

The scientists compared the change in tree density of the ant-plants and other trees at Lewa Wildlife Conservancy in central Kenya between 2003 and 2008. The vegetation lacking ant defenders notably declined, while protected trees suffered no significant changes in population.

"These tiny ants are actually major ecosystem players, capable of regulating woody plant biomass accumulation in a savanna, and stabilizing the tree population against catastrophic damage by elephants," Palmer said.

If ants can successfully protect an entire population of trees, there is hope that they can be used to prevent elephants from feeding on crops, too.

"There has been a lot of interest in the field of conservation about how to minimize the conflict that elephants have with people," Palmer explained. In a few severe cases, angry farmers have killed elephants and agitated elephants have trampled people to death.

Image: Zahra Hirji