Here's a rather interesting situation sent in by Olivia....
Background: We have an outdoor cat and 2 indoor dogs who go outside
(fenced in back yard) during the day when we are at work or away. They
have access through a dog door into a heated garage with carpeting and
dog beds. The cat spends most of his time in the backyard with the dogs.
He will even arrive at the back door in the morning to greet the dogs
when they are let out. They all seem to get along. The dogs are both
female. One is about 3 years old and 20 lbs. The other is 11mos and 12
lbs. The older dog will often go up on the picnic table (which the puppy
cannot get up onto) and sunbathe.
The other day I came home to find the female dog mounting the cat and very actively humping him (I'm not sure what other word to use here). They were both on top of the picnic table. The puppy was below bouncing around below trying to see what was going on. I have never seen something so weird before in my life. I know some female dogs will mount other dogs out of dominance, but why would she be mounting the cat and more importantly, why would the cat be allowing it? When they noticed me, the dog came running over and the cat laid down on the table to roll around and then proceeded to lick/clean hi crotch. He was obviously not distressed or trying to get away.
What is going on?
The other day I came home to find the female dog mounting the cat and very actively humping him (I'm not sure what other word to use here). They were both on top of the picnic table. The puppy was below bouncing around below trying to see what was going on. I have never seen something so weird before in my life. I know some female dogs will mount other dogs out of dominance, but why would she be mounting the cat and more importantly, why would the cat be allowing it? When they noticed me, the dog came running over and the cat laid down on the table to roll around and then proceeded to lick/clean hi crotch. He was obviously not distressed or trying to get away.
What is going on?
When someone sees a dog "humping" or "mounting" (both appropriate terms) it is usually assumed that the behavior is sexually related. However, we can see this happen in pre-pubertal dogs as well as females. In the former there is no sexual drive yet and in the latter, well, they simply don't do that during sexual intercourse. So why do such antics happen?
Mounting does have an obvious sexual function and is a normal behavior during sexual arousal. In neutered or pre-pubertal males you can see them humping pillows and stuffed animals as a form of masturbation. Even though they don't have the testosterone stimulating the behavior, they do get some physical pleasure from the act.
But sex certainly isn't the only reason for dogs acting this way. As Olivia mentioned, dominance is one potential cause. In humans many sexual behaviors have their origin in a desire to dominate rather than just sexual pleasure. Many animals will mount subordinates in their social group as such a sign of dominance. However, there are also other reasons for dogs to mount, and I don't think Olivia's dog is being dominant.
One of the most common reasons for humping is excitement and over-stimulation. When a dog is playing and has lots of stimulation going on, it will trigger centers in the brain that can lead to mounting behavior. One of my own dogs does this! Inara is a three year-old lab mix, and not particularly dominant. Overall she's pretty calm and laid-back. Yvaine is our very playful 1 1/2 year old lab, whose favorite game is tug-of-war. When they're playing by themselves, I don't see any humping from Inara. But many times when I'm playing tug with Yvaine, Inara will want to join in on the fun and will start to nip or paw at Yvaine. This isn't mean and is just Inara's way of saying "Hey, don't leave me out." Often I'll see her try to mount Yvaine and start humping. I can tell that she's not being dominant and is just wound up because of the play that she isn't a part of. The only way to stop this particular form of behavior is to avoid the excitement, which obviously isn't always possible.
Olivia, my suspicion is that your dog was mounting the cat because of some kind of mental over-stimulation or excitement. Maybe she was playing with the puppy, or the puppy was aggravating her, and the cat just happened to be there. In a spayed female towards a cat there certainly wouldn't be anything sexual. And dogs generally find other ways to be dominant, especially towards cats. Without observing the situation myself or seeing a video I can't say for certain, but I would strongly suspect that this falls in the excitement/stimulation category.
But what about the cat? Why would he tolerate this?
Some cats are very bonded to the dogs in their family and are particularly docile. One of my own cats, Tristan, is such a cat. Many times we have seen the dogs, especially Yvaine, mouthing him and virtually chewing on him like he is a toy. They are gentle and don't do any harm, but they are definitely working him over. Sometimes we've seen him walking around with his fur wet and sticking up in odd directions and know that the dogs have been on him. What is strange is that he tolerates this treatment. He will just lay there letting the dogs chew, though he does have a rather pitiful expression on his face. When they are done or when they look up, he just calmly gets up and walks away. He is definitely the sweetest and most tolerant cat I've ever known.
Here's my reconstruction of what may have happened with Olivia's pets. The dogs were outside, perhaps playing, and maybe the puppy was bothering the older one a bit. She jumped up onto the table as is normal, and there was the cat. The dog was over-stimulated and the cat was in her place, so she started humping him. He knows the dogs well, is a calm cat, and wasn't being hurt, so he just lay there, not really knowing what was going on. After a little bit the dog stops and the cat gets up. As I said, I can't prove this, but from what I know of animal behavior this is a reasonable assumption.
I hope this helps Olivia as well as others that have dogs who do similar things.