It’s a classic David and Goliath story, except there are 90,000 Davids and they all have stings. On the African plains, the whistling-thorn acacia tree protects itself against the mightiest of savannah animals – elephants – by recruiting some of the tiniest – ants.

Elephants are strong enough to bulldoze entire trees and you might think that there can be no defence against such brute strength. But an elephant’s large size and tough hide afford little protection from a mass attack by tiny ants. These defenders can bite and sting the thinnest layers of skin, the eyes, and even the inside of the sensitive trunk. Jacob Goheen and Todd Palmer from Kenya’s Mpala Research Centre have found that