Well no, not while they're being raped they don't. It's a very traumatic experience. Their silence shouldn't necessarily be interpreted as willingness.
Now you are making me think back (35 years) to the days when Jane and I used to wear our leather shorts rock climbing. Those were the days....
My first orgasm happened when I was climbing a tree as a 12 year old. I didn't know what was happening to me, but it really felt good.