Dogs and cats can get along famously, despite the natural sources of friction that exist between a solitary animal like your domestic cat and a pack animal like Ruff. At any rate, your successful and hassle-free introduction sets your pets off on the right paw.
When a dog joins your household, your cats will benefit from having a space they can get to that is out of the dog’s reach. If you haven’t already done so, clear a shelf or make some room at a suitable elevated position so the cats can escape from the attention of the dog. Similarly, each room should have an unobstructed escape route for the cats, so they can get away from the dog. A cat who feels trapped is more likely to become aggressive toward a dog.
Before you introduce the dog to the cats, take the pup for a long walk and play some stimulating games with him. This will help him get rid of excess energy, making it more likely that he'll act calmly when faced with the cats. Feed the cats prior to their introduction to the dog. Well-fed cats are more relaxed than hungry cats.
The First Introduction
Cats and dogs don’t speak the same lingo, so a defensive gesture from your cat, such as rolling onto her back, may be misinterpreted by the dog as being a submissive gesture. For this reason, it pays to leash your pup on the first introduction so you can physically restrain him if necessary. It's also recommended to allow a cat and dog to "meet" for the first time through a closed door. This allows the two to investigate each other's scents before seeing each other face-to-face. Keep the first meeting brief and reward the pup for calm, passive behavior while he is at a good distance from the cat. During this event, you let the cat make decisions. Let the cat come to the dog on the cat's time.
When to Retreat
If either cat or dog becomes distressed, aggressive or anxious, end the introduction by calmly walking the dog out of the room. It’s important to remember that the cats are the resident animals and the dog is entering their territory. Cats are much less tolerant of new animals invading their space than dogs are, so look out for signs of stress in your cat during and after the introduction. Also, be prepared for your dog to chase if the cat darts away from the dog. Sometimes this sudden movement by a cat can trigger an otherwise calm dog's prey drive. A dog-cat chase will only increase tension between the two pets.
Some basic obedience training for your pup will help massively. After the initial introduction, teach your pup the sit, stay and recall commands. Use brief, frequent training sessions away from the cats to do this. Once he's mastered these commands, it won't be necessary to leash him when he interacts with the cats.