Pigs have previously been trained to find truffles and narcotics, and now, also mines. In Israel, of all places.
The Wonderful Pig of Knowledge writes about Giva Zin and his sapper pigs. He has also linked to an article about Zin by Jeanette Townsend at MAIC, and the London Imperial War Museum's exhibition Animals at War.
Other animals used by armies around the world throughout history are, for instance, horses, camels, donkeys, mules and elephants (cavalry and transport); pigeons (messengers); dogs (messengers and a variety of life-saving missions); rats (detecting mines); dolphins and sea lions (detecting mines and other objects under water).