Bringing a new puppy home can be overwhelming for everyone, including your other pets who were already there! The best way to ensure a smooth introduction is to make it slow, deliberate, and supervised. You don’t want either the new puppy, or your other pets, to be stressed by the experience.
Introducing to a resident dog
As long as your resident dog has no problems with leash-reactivity (becoming anxious or aggressive when meeting new dogs on a lead), then having them on a lead is useful initially so you have a little more physical control over the introduction and can gauge how your adult dog will react to a new puppy. The best timing is a little while after the resident dog has had a good walk or play session, to tire them out a little. The best space to do this introduction would be in your garden or a large room with plenty of space.
If your older dog ever gets reactive or frustrated on a lead, then you should skip step 1 and allow the dogs to meet in an open space, off lead. Make sure this is a controlled environment and you can get hold of either dog immediately if they become distressed.
Hold the puppy in your arms or on a lead at a short distance away. Have someone walk the other dog past the puppy, allowing them a friendly sniff if they want to.
If this walk-by goes well, allow the dogs off their leads to interact freely with each other, for just a few minutes. Then separate the dogs and try another intro session a few hours later. Keep these sessions short, so you are minimising the chances of either dog becoming frustrated.
During the off-lead meet & greet, place furniture or props of varying heights around the area. Having a high location available (eg. a bench or chair) allows adult dogs the option to jump up and escape the puppy for a few seconds if they need a bit of time out. This means the older dog does not have to resort to snapping or snarling at the pup to get their point across, and the scenario will be more relaxed even if the puppy becomes overexcited. Similarly, having a low location available (eg. under a chair/bench or in a small play tunnel), allows the puppy the option to duck into a space away from the larger dog, if they feel nervous.
For the rest of the day, either keep the dogs separate or very closely supervised if they are together. Gradually over a few days, if the older dog shows no sign of distress or aggression about the new puppy’s presence, they can spend more time together.
For the first few weeks, make sure you are removing toys or chews from any shared space so the dogs cannot fight over resources, and always feed them separately. These things can be slowly re-introduced once the dogs have established a good relationship.
Introducing to a resident cat
Cats can be sensitive souls, and the social dynamics of the house are very important to them. Introducing a new puppy can be stressful for a cat, so it is best done in careful stages.
Keep your puppy and cat separate for the first few days. Use doors and baby gates to keep them in different rooms. Allow your cat to walk through rooms where the puppy has been so they get used to their scent.
After a couple of days, once the cat is used to the concept of someone else being around, allow them to see each other. This could be with the puppy calmly on your lap whilst the cat walks through the room, or by allowing the animals to look at each other through a glass door or baby gate.
If the cat shows no sign of distress at the puppy’s presence, you could let them sniff each other. Only do this with a calm puppy, in your arms or on a lead so they can’t jump on the cat with excitement. Do not force this interaction; allow the cat to come to you and the puppy, or to maintain a safe distance from you both, if they prefer. Some cats will be confident and cuddly around dogs, others will never want to have close contact with them, which is fine.
Once both animals have become used to each other, it is safe to allow them both access to the same spaces. Always supervise these interactions in the early weeks. It is always a good idea to provide the cat with easily accessible, elevated escape locations where the dog can’t reach them in a chase, eg. a cat tree, elevated shelf or ledge.
Consider using the pheromone spray or plug-in ‘Feliway’ to help keep your cat relaxed despite their newly acquired sibling.
Introducing to other pets
If you have birds, rodents, rabbits etc. in the house, it is safest to keep these animals completely separate from your dog, especially at first. Always remember that some breeds of dog have been bred to chase, grab or shake small animals, and that even a friendly puppy will sometimes not know their strength when over-excited. For the safety of your other pets, it is best to allow your dog to see and sniff them, initially from a distance, then gradually closer. Always do this through a closed enclosure to protect the other pets and stop the interaction if your dog becomes over-excited or aggressive. Your aim is just to get your puppy used to the presence of these other animals. Over time you may discover that your puppy might not have a strong prey drive, and may be friendly or disinterested by these other pets, in which case they may be fine coming in close contact when supervised by you.