Tom Vanderbilt in Smithsonian Magazine:
There would be a rustle of oily black feathers as a raven settled on the window ledge of a once-grand apartment building in some Eastern European capital. The bird would pace across the ledge a few times but quickly depart. In an apartment on the other side of the window, no one would shift his attention from the briefing papers or the chilled vodka set out on a table. Nor would anything seem amiss in the jagged piece of gray slate resting on the ledge, seemingly jetsam from the roof of an old and unloved building. Those in the apartment might be dismayed to learn, however, that the slate had come not from the roof but from a technical laboratory at CIA headquarters in Langley, Virginia. In a small cavity at the slate’s center was an electronic transmitter powerful enough to pick up their conversation. The raven that transported it to the ledge was no random city bird, but a U.S.-trained intelligence asset.
Half a world away from the murk of the cold war, it would be a typical day at the I.Q. Zoo, one of the touristic palaces that dotted the streets of Hot Springs, Arkansas, in the 1960s. With their vacationing parents inca tow, children would squeal as they watched chickens play baseball, macaws ride bicycles, ducks drumming and pigs pawing at pianos. You would find much the same in any number of mom-and-pop theme parks or on television variety shows of the era. But chances are that if an animal had been trained to do something whimsically human, the animal—or the technique—came from Hot Springs.