Humping another dog is usually a dominance thing and guaranteed to piss the other dog off. Humping a human arm or leg . . I'm not sure.
That said, my little maltese, Casper (RIP) had a stuffed bunny that he humped ALL THE TIME but he never humped another dog or anyones arm or leg. So, in his case, I don't know. Perhaps he had sexual feelings toward the bunny?
I never had a problem with it since he limited all his humping activities to that one Bunny.
It did, however, drive my mother crazy, so I let it continue indefinitely.
It went on until the well meaning kennel that I boarded him at (of course I took his bunny) washed the bunny. After that, he never touched it again. And he never found another friend like that either.
Poor Casper.
