The legend is that a mouse can freak out elephants, but the truth is that their worst enemy is much smaller: ants. Elephants are scared of ants. That's what Jacob Goheen and Todd Palmer have discovered in Africa's sub-Saharian savannah.
Goheen and Palmer observed that during a really dry year most trees were obliterated by hungry elephant herds. Only a single species of tree stood up untouched: the Acacia drepanolobium, also called the whistling-thorn tree or ant tree.
These acacias are a refuge for ants. They feed them with a sweet substance and, in exchange, the ants will attack the elephants whenever they get near it, invading their trunks and biting them badly. The scientists tested this by feeding the plant to the animals with and without ants, as well as other species with and without ants. The elephants didn't touch any vegetation with ants in them.
After that, they altered ant population in the wild trees. The same trees, with no ants, got badly damaged by elephants. Their conclusion is that ants, the tiniest of animals on the African savannah, trump the largest animal in those fields. [Current Biology]