confused

Question
do dogs mate for fun even when bitch is not in heat?

Answer
No, they do not, and, actually, they cannot as they can only penetrate the bitch when she is in season and "prime" (near ovulation).

Mounting is one way dogs use to show dominance over another dog (or, in some instances, people around them); it is only sexual if the bitch is actually in season. (And bitches will often show mounting behavior, too.)

They will also mount bitches if the bitch should have some sort of infection, ie. a bladder infection, which is probably due to similar odors, possibly due to blood in the urine.