From vibrations alone, acacia ants can tell nibbles from the wind

Date:  February 15, 2019

Source:  Cell Press

Acacia trees are a prominent feature of the East African savannah. They're also a classic example of the long-standing and complex relationships between plants and insects, in this case acacia ants. The acacias provide food in the form of nectar and accommodation in hollow thorns for the ants. In return, the ants defend the acacias against nibbling elephants, giraffes, or other animals that would eat them.

Now, researchers reporting in the journal Current Biology on February 14 find that the ants are tipped off to the presence of herbivores by vibrations that run throughout the trees when an animal gets too close or begins to chew. As a result, the insects begin patrolling the acacia's branches more actively. Remarkably, the researchers show, the ants don't react when the trees' movements are caused only by the wind.

"The vibrations that occur when a mammal plucks a leaf are so powerful that they spread across the whole tree and are perceived by the ants," says Felix Hager of Ruhr University Bochum, Germany. "As a result, the ants are alerted within a fraction of a second and promptly orient toward the attacker."

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