Introducing a New Pet to the One You Already Have

Introductions fail for one reason more often than any other: speed. The new animal is in the living room within an hour of arriving, because everyone wants to know whether they will be friends. Both animals remember that first meeting, and a bad one can cost two months.

Start on neutral ground. For two dogs, do not meet in your home, your garden or your street — your resident dog owns all of it. Meet in a quiet park or unfamiliar street, one handler per dog, loose leads, never nose to nose. Walk them parallel, three to five metres apart, in the same direction, for ten to fifteen minutes, and close the distance only as both dogs stop staring and start sniffing the ground. Sniffing the grass is not rudeness; it is a calming signal. If they greet, allow three seconds, then call both away and keep walking. Then walk home together and go through the front door side by side.

Cats do not do introductions in an afternoon. Set the new cat up in a closed room with everything it needs and keep the door shut for the first several days. Swap scent: rub a soft cloth on one cat's cheeks and leave it under the other's bowl. Then feed both cats on either side of the closed door, moving the bowls closer over a week or two. Only after that swap their territories for an hour a day, and only after that use a barrier they can see through — a screen door, or two stacked baby gates. Expect two to eight weeks, sometimes longer, and expect to go backwards when it goes wrong. A cat that hisses through a gate is doing the introduction correctly.

Then manage the resources, because that is where the real fights happen. For the first two to four weeks, feed in separate rooms behind a closed door and pick the bowls up afterwards. Remove high-value chews and toys entirely. Provide more beds than animals, in different rooms. Look hard at your doorways and the top of your stairs: narrow places where one animal can be trapped or blocked cause more conflict than food does. With cats, never leave only one route to the litter tray, and give each cat a tray plus one spare. And be honest that you are a resource: many first fights happen at your feet when you come home. Greet the resident animal first, every time, and never stroke one while the other is elbowed out of the way.

Do not leave them alone together until you have had two clean, boring weeks with nothing to report. A gate or a crate is not a failure; it is what makes the friendship possible.

Slow down when you see a hard stare held for more than three seconds, a stiff body with a closed mouth, raised hackles combined with stillness, one animal blocking a doorway, or growling that gets faster rather than louder. Slow down harder if a resident cat stops using the litter tray, hides for more than two days, or if either animal starts skipping meals.

Get professional help — a qualified behaviourist, and your vet first if there is any injury — when a fight has had to be broken up physically, when one animal cannot be walked past the other without exploding, or when a cat has refused food for a full 24 hours, which is not something to wait out. Repeating a failed introduction more forcefully does not work; you need someone to watch your animals and rebuild the plan.