Dr. Kirk Langstrom, a zoologist who specialized in the study of chiropterology, developed an extract intended to give humans a bat's sonar sense. He tested the formula on himself because he was becoming deaf. The extract worked, but it had a horrible side effect: it transformed him into a hideous man-sized bat.[3] The serum also took away his intelligence, so he went on a mad rampage until Batman found a way to reverse the effects.