1. Confine your new pet to one room for up to a week. Provide the cat with its very own toys, bed, litter box and bowls of food and water in that room (bathrooms are ideal because there are no hiding places). Choose a space that is not the location of the “old” cat’s litter box or feeding place.
2. Every day for the first week try rubbing a little baby powder, your favorite cologne, or even your gamey gym socks on both cats/dogs so when they sniff each other they both find the smell familiar. “Aha! I know you… you smell like me!” Let them sleep on your worn clothing (with your scent).
3. Take a piece of string and tie a ball of aluminum foil (or similar toy) on each end. Put one end in the new cat’s room and the other out in the hall. When your new cat pulls, the existing cat will play with it and visa versa. This puts them nose to nose under door.
4. Mid-week, carefully move the new cat to another room to explore for a brief visit. Let the existing cat(s)/dogs into the new cat’s lair. Let them sniff, eat, drink and use the litter box. Then move the new cat back into its lair, replace the string toy, and close the door.
5. On the seventh day, open the door and let the cats/dogs find one another. Expect some hissing and posturing – it’ll pass with your calm support.
