dogs of both sexes, fixed or not will hump. This is a show of dominance. Your female dog is letting your smaller male dog know that she is the boss. The leader of their pack.

It is a display of dominance.

She's trying to say "I'm the boss of you!"

As correctly shared by several others here....Dogs, "fixed" or not, males and females WILL, on occasion, hump. Since you say that this seems to happen when they are fighting...it is most likely a show of Dominance. Your Female wants everything to be PERFECTLY CLEAR to the Male that she IS, in fact, the BOSS OF HIM! On occasion, I've seen humping take place during what was clearly a rowdy play session as well, even with spayed and neutered bitches and dogs. More like a mutual agreement of "I'll hump you, then you hump me and oh we're having such fun today...la, la, la, la, la!" Even between two dogs or two bitches no overt signs of stress or dominance, just an evident game of "Slap and Tickle!" If your dogs are having actual fights...then there are two problems.....(Of course, it is possible one of them could be injured...and that's never good!) But...one would be that both dogs are Beta's. Neither one is a TRUE ALPHA...since True Alpha's do not usually start or participate in FIGHTS...they rule with benevolence! The second problem, and far worse...is that neither of the fighters BELIEVES THAT YOU...ARE THE HEAD ALPHA in their world! Bata dogs will sometimes get into a scuffle or think of doing so...because both want to move up the old ladder towards being a leader of the pack. However, in a healthy canine relationship...our dogs come to understand and believe that WE are the true leaders in the home, even if one of them is an actual Alpha temperament. They defer to OUR wisdom not due to any FEAR issues...but because they have learned through our training them, that WE almost always have the very BEST (high value rewards) IDEAS! You may want to start working with these two, before one of them gets accidentally hurt during one of their fights. Good basic training on all of the most common commands should help them to realize that YOU are the real Alpha and that they need to respond quickly to your commands and not even THINK about fighting! The Come, Sit, Stay, Lay down, Back up, Get up, Get off, Leave it, Drop it, Give it to me, No Bark! Should give them something to learn and do rather than piss each other off...AND will give you some excellent behaviors to use on them, when they are about to make a poor choice as to their behaviors! Using +R, Positive Reinforcement training methods, will keep it fun, and exciting, utilizing not only their physical energy but stretching their minds a bit too! (Instant Enrichment! Fun!) Fun, Praise and Treats are the key to success, along with daily practice times! No more than 30 minutes per dog, as long as they are over 12 to 14 months of age....shorter for younger dogs/puppies! Always remember to use HIGH VALUE treats, you are out to impress them with a good reason to want to learn! AND...if you are not smiling....your dog probably isn't having fun either! Happy Tails!

Dominance