This Fence Made of Bees Keeps out Elephants

Elephants can be beautiful and majestic, but they're also a nuisance when they trample crops. That's a problem in eastern Africa. Zoologist Lucy King developed a novel solution.
Elephants are afraid of bees because stings inside their trunks are very painful. When they hear bees, they run away. So King invented this fence that consists of a long string of wire with beehives every 10 meters. When elephants hit the wire, they rile up the bees, who leave their hives to swarm and attack. The sound of the bees drives away the intruding elephants. Edible Geography describes what is sometimes called the "honey fence":

A pilot honey fence in 2009 proved successful, deterring all but one bull elephant, and The Elephant and Bees Project has since spread to sites across Africa. Neville Sheldrick of the David Sheldrick Wildlife Trust told Africa Geographic that nearby farmers are sure the fence is working: “When I visit they proudly walk me around showing me the footprints of elephants that have walked up to and along the fence in several locations before turning back towards the park.”
By encircling a village with a cordon of hives, the village’s crops are protected, the elephants steered away from potential conflict, and, adds Carr-Hartley, “the farmers are able to garner some revenue from the harvesting of honey.” The result of truly delightful example of interspecies landscape engineering, jars of “Eleephant-friendly” honey are for sale at The Elephant and Bees Research Centre in Tsavo, Kenya.