Aggression between cats, or one cat bullying another, can be a very complex issue. Cats can form deep bonds with other cats, and there are many cats who prefer to have company. However, cats are also very territorial by nature and issues can develop between cats who share territory, especially indoor territory. Aggressive behaviors can look as overt as yowling, hissing, and fighting; and as subtle as staring or even laying in areas that block another cat from resources such as the food bowl, litterbox, or preferred sleeping areas.
Inter-cat issues most commonly occur when a new cat is introduced to the home, and introduced to the resident cat(s) without proper introduction time. To help prevent this issue, introduce your new cat very gradually. Set your new cat up in a private room with a complete set of its own resources (food, water, litter, scratching post, cat tree, toys). Allow the resident cats to sniff through the closed door for a few days, and switch a few toys or blankets to allow them to acclimate to the scent of the other cat. The next step is to allow them to see each other through a baby gate or at opposite sides of a large room. They should be allowed to see and sniff each other, but not be left loose to escalate to hissing or fighting. The final stage of introduction is to allow them to meet. Reinforce and allow curious or friendly greetings, such as nose touches, rear end sniffing, or playing. Increase distance between the cats if you notice intense staring, hissing, or swatting.
Even when the cats are allowed to interact freely, it is important to have multiple sets of resources throughout your home. Most points of tension occur around food bowls or litterboxes. Make sure you have multiple feeding stations and areas where litterboxes are placed in your home.
It can also help reduce tension between cats to diffuse Feliway throughout your home. This is a synthetic pheromone that helps create harmony and reduce stress in a multiple-cat home.
If aggression suddenly develops between two cats that have previously been living in harmony, please book an appointment with your veterinarian as this may be a sign of health issues.