How ants persuaded lions to eat buffalo

“The ant and the zebra” sounds like the title of one of Aesop’s fables. Like all good fables, this one has a moral, which is that tinkering with nature has unpredictable consequences. Unlike the Greek originals, though, which were allegories, this fable is real.

The story plays out in Laikipia county, Kenya, not far from the mountain which gave that country its name. The characters include big-headed ants (an invasive species of obscure origin), the native acacia ants these interlopers have gradually been replacing, the whistling-thorn trees in which both sorts of ants live, a cast of elephants, lions, zebras and buffalo, and Douglas Kamaru, a Kenyan biologist who currently has a berth at the University of Wyoming. As Mr Kamaru and his colleagues report this week in Science, the ant invasion has triggered a convoluted chain of consequences which has helped zebras at the expense of buffalo—thus neatly illustrating a phenomenon called “trophic cascade”.