[header] How to introduce new pets [title] Research the realistic compatibility of your new pet being housed with your old pets, preferably before you select your new pet. [step] In addition to predator/prey relationships, some animals can be very territorial and aggressive towards members of their own species. Learn what you can beforehand and you'll have a better idea of how much peaceful interaction you can expect your animals to have. 
[title] Consider the personality of your current pet or pets. [step] Think about how your pet acts around you and around other animals.