Introducing a new cat to your pets
Cats tend to hold on to their initial impressions for a long time, and it's rarely "love at first sight." Rather than introducing cats suddenly, we recommend slow introductions. That means keeping the cats separate for a period of time that can range from a few hours to a few weeks depending on the cats' needs. You introduce them "one sense at a time," allowing them to become acquainted through sound, smell, sight, and so on. If they ignore each other during the process, count that as a victory. The goal is to keep them calm and thinking "I've got this" throughout. Here is a link providing many more details of how to introduce two cats slowly; the techniques also apply to introducing cats to dogs:
Read: http://www.catbehaviorassociat
If you prefer videos, this one provides a lot of helpful guidance:
Watch: https://www.facebook.com/Colea
