This behavior is a show of outright dominance over your cat. It is your alpha dog trying to display to your cat that they are in charge. It is an interesting habit and very common in young dogs and smaller breeds and can display itself in a variety of different dogs and situations. How does it start and what can you really do about it? Although we can influence this behavior, people struggle with it every day. Some of these frustrations we can do something about so let's walk through the root of the behavior and what our potential solutions are.
The Root of the Behavior
Well, your dog may likely believe this to be a game. A game played between your dog and your cat, and unbeknownst to your cat, your cat likely told your dog that this is a game. Dogs communicate through body language and actions, and whilst cats do the same thing, they may not always get the same message across. If when your dog sits on your cat, your cat swipes at him and chases your dog around, then your dog has likely learned that reaction and believes it to be a game. Therefore each time your dog sits on your cat he believes to be initiating a game, and each time your cat reacts like that they are, without knowing, reinforcing that principle to your dog. After many repetitions of this cycle, the behavior becomes very ingrained. As time goes on it will become harder and harder to adjust this behavior as your dog will simply not know what they are doing to upset you. Does your dog have a particular spot they always sit? Is it when they are going to this spot that they sit on your cat? In cases like this, your dog is simply asserting his dominance in the household and your cat will likely learn that they cannot sit in that particular spot. Often, early on, this behavior will cause some contention but will eventually subside as the natural relationship between your cat and dog form and they both learn how they should behave if they do not want to upset the other. Finally, your dog may like to sit on something warm. Your cat is a rather large heated pillow with a soft outer layer and comfortable head. It may have nothing to do with your cat really, but just them seeking a warm spot to sit. Once they sit on your cat, your cat will likely run and move, leaving the spot that they have warmed free for your dog to take.
Encouraging the Behavior
Depending on what is causing the behavior there a quite a few things you can do to keep that dog butt off your cats head. Creating a separate area that your dog can call home is going to make a big difference. Although many people use the kennel for this area the only important bits are the dog bed and some things the dog enjoys. Lay out their favorite blanket, a stuffed animal they like and some toys around that they enjoy. Canines are denning creatures and those behaviors will take over. They will choose the area they consider their home to sit over the area your cat has made warm. Creating an area for your cat specifically may help, especially if this area is removed from the reach of your dog. This way the dog simply cannot sit on them even if they wanted to. Try setting a dark blanket or small pillow on the back of your couch, once your cat gets used to sitting in this area your dog will no longer be able to bother them. If, however, they do this because of how your cat reacts and they consider it a game, it may be a bit harder to break this behavior. A trainer or behavioral specialist may be your best bet as they will be able to discern what is causing them to act this way and what you can do to correct this behavior.
Other Solutions and Considerations
Poor kitty, getting sat on all the time. All they were hoping for was a nice spot to lay their head and your dog has to come and ruin it for them. The good news is, as your dog gets older, this will likely stop as time goes on. If it does not, then a few best practices around the home will make a marked difference in your pup's behavior. Make sure both your cat and dog have designated spots in the home to lay, this will ensure they are not fighting over the same space and over time will eliminate most the contention.
Regardless of why your dog is sitting on your cat, but if it does not change with time alone then you should be able to fix this pretty easily. Dogs and cats are renowned for having an issue getting along, but once they have their separate areas and a separation of belongings this will get way easier to deal with.