When I was at the Phoenix zoo some years ago I walked up next to a large enclosure that had a beautiful panther - a black leopard - inside. He was called Eldridge, I think, (after Eldridge Cleaver, of the Black Panthers, I guess) and had been the mascot of a combat brigade in Viet Nam. Eldridge must have been lonely, because when I walked up to the enclosure he rubbed his face and shoulders against the cage and purred, or rather rumbled, like nothing so much as a giant, friendly house cat. I wanted to scratch him behind the ears, but contented myself with telling him how handsome he was - all cats like flattery, and he was no exception. (And yes, I know he couldn't understand English, but I think he recognized my approval and good intentions toward him.)