Before purchasing a second animal, do your research to find compatible pets. For example, if you have a Jack Russel, you want to avoid buying cats or smaller animals because Jack Russels are hunters and may attack the new pet. Understand the Behavior Before you can address the behavioral problems, you need to understand the motivation behind them. For example, is your dog afraid of the new pet, or does it appear angered by it? Fear and anger may present similarly through barking, growling, or hissing, but they are two distinct emotions. Provide Individual Space The best way to introduce animals to each other is by providing time and space. Whenever possible, set up a quarantine room for your new arrival. Use Positive Reinforcement When you introduce your pets, you want to praise positive behavior. For example, when your new pet is behind a spare room door and your existing pet shows interest, happiness, or excitement, give them affection. Desensitize and Socialize When the new pet is ready, you can remove the gate and let them roam the house. It is best to lock your other animals up and give the new pet a few minutes to explore independently. Once it has had time to adjust to the extra space, let your other pets out, one at a time. You can consult a trainer or other pet professional if all else fails. Remember, the key to successful introductions is control and pace. Control the spaces and keep the process slow.