Ants
In the savannas of Eastern Africa, some ants live in the thorny, hollow bulbs of acacia trees and feed on the trees’ nectar. These ants also act as bodyguards, defending the trees from hungry elephants and giraffes by biting and stinging them. Now, an invasive species known as the bigheaded ant is killing the native ants. The native ants put up a brave fight, streaming out of the acacia trees to meet the invaders, but the invasive species usually wins in a hostile takeover of the trees, says Corinna Riginos, an ecologist at Teton Research Institute. “There are body parts strewn everywhere,” she says. The bigheaded ants, Pheidole megacephala, stay a while in the acacia trees before returning to their nests, preventing native species from recolonizing the trees.