
I can't tell you why (I have a bitch that does it), but years ago I had a Toy Poodle bitch that was spayed. Our draught excluder was called Horace (a snake), and Cindy used to bend him in half and get him between her legs. She would hump like fury, and when he fell out of the right position, she would get mad with him, and shake him like mad! ;-)