Don't be alarmed; it's normal for cats to hiss at something new or something they don't understand. Hissing is a distance-increasing behavior. Simply put, it's a warning saying, “Please back off, and do not come any closer.”
Don't interfere in their interaction unless necessary—Some hissing and growling are normal and will stop as the older cat gets used to the kitten. Step in and separate the cats only when the situation escalates.
Your cat does not want to give up any of your affection or attention to this newcomer. They may hiss to show that they are not welcome. When bringing a new kitten into the home, it must be done carefully and gradually. Patience is key here, but with time a full introduction can be smoothly accomplished.
Quick Overview. Older cats hissing at a new kitten in the household is totally normal behavior. Cats usually stop hissing at a new kitten with time and a careful, gradual introduction. Giving your cat plenty of space, time, and positive reinforcement to get used to a new kitten will make for a smoother transition.
Jealousy over the presence of another cat is very common. All cats have different personalities, and some will be made insecure and display jealousy more easily than others. It is important to watch your cat and observe their cues and triggers.
Introducing too quickly with little preparation will often lead to cats feeling threatened and scared, which increases the chance of aggressive behaviour being shown. Once cats feel this way about each other, it can be extremely difficult to change their minds.
When you introduce them to each other in the same room, a bit of growling and hissing is to be expected. Although the two cats may be used to each other's scent; your first cat will still feel a bit awkward with your new cat being in his territory.
Cats are predators, and kittens are prey, so it's natural for an adult cat to want to kill a kitten. However, some cats are more likely to kill kittens than others. The first factor that affects a cat's propensity to kill kittens is whether the adult cat has been socialized with kittens from an early age.
Age and temperament are the most important factors. Adult cats will usually accept a new kitten much more easily than they will accept a new adult cat. Cats are territorial, and your cat may resent an adult feline intruder.
The introduction must be gradual. Following the initial introduction, it can take a very long time for a relationship to grow. It takes most cats eight to 12 months to develop a friendship with a new cat. Although some cats certainly become close friends, others never do.
Fortunately, neutered and spayed cats are much more likely to get on well together than intact adult cats. Generally, female cats tend to be more accepting of new cats into their home. They are more likely to accept another female cat than a male cat.
Each day, have the cats switch rooms so that they both experience some variation and get access to each other's scents. You may need an assistant to do this safely. After several days, if both of your cats appear relaxed, crack the door open one inch. If they remain calm, open the door a bit more, then a bit more.
Signs of conflict between cats can be open or silent. Signs of open conflict are easy to recognize; the cats may stalk each other, hiss, and turn sideways with legs straight and hair standing on end up to make themselves look larger. If neither backs down, the displays may increase to swatting, wrestling, and biting.
Hissing Is a Form of Communication
For cats, a hiss or even a growl is part of their communication style. You might think it's the same as physically punching someone—an act of anger. But often, it's more of a warning and a way of saying, "Hey, I'm feeling uncomfortable and vulnerable, so give me some space."
If one or both of the cats are intent on chasing and can't be redirected into another activity, it's time to take a step back. Work your way back through the introduction steps, really focusing on building a relationship through food and mutual play at the door of the new cat or kitten's acclimation room.
Even in the absence of physical aggression, introductions can provoke anxiety that leads to inappropriate elimination, decreased appetite, or other signs of stress in one or both cats. Fortunately, you can increase the likelihood of a successful introduction by introducing two adult cats slowly and gradually.
Remember, the worst thing you can do for any kind of in-person/no barriers introduction, is to bring both cats into a shared space without giving them something to do. In that ill-advised scenario, the other cat becomes their “something to do,” and you'll likely find that the “staredown” soon turns into a “throwdown.”
You can test this by following a simple 3 second rule: If you pause after 3 seconds of stroking your cat, do they try to reinitiate contact (i.e. rub against you)? If not, your cat has probably had enough for now!
When bringing a new cat home to meet your resident cat, it's never a good idea to just throw them into a room together. That can be scary for both of them! Go slow and introduce them. For both animals this can be a stressful time.
All cats are individuals, and some tolerate new feline presences better than others. This process can vary from a few days to several months. It is best to follow your cat: check their body language and try and interpret if they feel comfortable or not. Only progress to the next stage when both seem relaxed and ready.
It can take a few weeks for pets to adjust to a new environment (and new animals), but with patience, your older cat will (hopefully) accept your new kitten. As pet parents, we can help our furry friends live their best lives.
The transition to adulthood ordinarily occurs from 1 to 2 years old. At this time, and possibly after neutering, a cat may retain a lot of energy but should be notably calmer with it reaching full maturity at 2. From 3 to 10 years old, a cat is relatively calm but remains active.