"To load a bomb aboard a bat, technicians attached the case to the loose skin on the bat's chest by a surgical clip and a piece of string. Groups of 180 were released from a cardboard container that opened automatically in midair at about 1,000 feet, after which, says the CWS history, "bats were supposed to fly into hiding in dwelling and other structures, gnaw through the string, and leave the bombs behind."
In May 1943, about 3,500 bats were collected at Carlsbad Caverns, flown to Muroc Lake, Calif., and placed in refrigerators to force them to hibernate. On May 21, 1943, five drops with bats outfitted with dummy bombs were made from a B-25 flying at 5,000 feet. The tests were not successful; most of the bats, not fully recovered from hibernation, did not fly and died on impact."