Introducing Cats: The Slow Way Is the Only Way

The most common mistake is speed. Two cats pushed nose to nose on day one can hold a grudge for years, because a cat's first impression is territorial and scent-based, not social. Plan in weeks: two to six is typical, some take three months. That is not lost time; it is the cheapest thing you will ever do for a peaceful house.

Set up a base camp before the new cat arrives: a room with a door that closes, holding a litter box, food, water, a scratching post, a high perch and a hiding place. The newcomer lives there, with no sight of the resident cat for three to seven days, while he settles enough to eat, use the box and come out from under the bed.

Swap scent first. Rub a clean sock gently on one cat's cheeks and chin and leave it in the other cat's space; do the same in reverse, and swap bedding daily. Then site-swap: shut the resident in another room and let the newcomer explore the house for half an hour. Each cat learns the other exists, and where it has been, without a body to defend against.

Next, feed them on either side of the closed door. Two bowls, both far enough back that each cat eats calmly; at every meal, move each bowl a hand's width closer. If either one stops eating, stares at the door, hisses or leaves the food, you have gone too fast: return to the last distance where both ate happily and hold it three or four meals. Repeat until both eat right against the door.

Only then visual access, and only through a barrier: a door wedged open a few centimetres, a tall baby gate, a mesh screen. Keep the first sessions to five minutes. Feed or play with both cats while they can see each other, and stop while both are still relaxed — always end on a good moment, and never let a session run until it goes wrong.

Physical access comes last: a short supervised session in a large room with two exits and high perches, with a wand toy in the air so nobody has to stare at anybody. Two or three minutes, then separate.

Failure is quiet before it is loud: a hard, unblinking stare; ears flattened sideways; a low growl; one cat parked in the doorway, or between the other and the food or the box; a cat who stops eating, hides all day or urinates outside the box. A swat with the claws in, or a chase that stops, is ordinary; screaming, flying fur, or a cat too frightened to come out means you skipped a step. Back up one full stage, hold it four or five days, and come forward more slowly.

Remove the reasons to compete: one litter box per cat plus one, food stations in separate rooms, plenty of vertical space and hiding places. Most household cat aggression is an argument about resources.

A resident dog is a different job. Train him before the cat is in the room: a solid sit, a reliable leave it, a settle on a mat. Then keep him on a lead, far enough away that he can look at the cat and then look back at you for a treat — you pay him for turning away, not for staring. Keep sessions short. The cat needs high shelves and a room with a gate she can pass and he cannot. Never let him chase her, not once, not playfully: one chase teaches a game that takes months to unteach.