Examination of pathologies in a series of felid skulls from a museum collection spanning the past century revealed distinctively malformed external occipital protuberances in zoo specimens of Panthera tigris, a condition that was not present in the skulls of wild-caught individuals. Myological studies and comparative dissections together support a conclusion that the condition most likely arose from heightened rotation of the head and neck in the lateral plane, combined with reduced jaw activities during the lives of the affected individuals. Historical records in turn indicate that such activities were possibly consequences of the nonnatural diets and increased grooming behaviors fostered in captive environments. Zoo Biol 17:135–142, 1998. © 1998 Wiley-Liss, Inc.