On Kenya's savanna, good fences make bad neighbors. Protecting acacia trees there from giraffes and other browsers sets off a chain reaction that ruins the partnership between trees and their bodyguard ants, says Todd Palmer of the University of Florida in Gainesville.
He first noticed something odd about the protected trees when walking among whistling-thorn acacias cordoned off since 1995. With hole-riddled thorns, the wind whines through these acacias, which are "spindly, knobby trees" at best, Palmer says. Those behind fences looked even worse.
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