Why Are My Cats Fighting All of a Sudden?

Stephanie Dube Dwilson

If your cats start hissing and clawing out of nowhere when they used to be friends, you might find yourself wondering, "Why are my cats fighting all of a sudden?" What was once a happy friendship has now turned into bullying and flying fur. Whether they're fighting because they smell differently or got spooked, your cats probably won't stay enemies for long. Here are some reasons why your cats don't get along anymore, as well as steps to help ease them into a friendship again.

One Cat Smells Different

If one of your cats suddenly smells differently, the other cat may react pretty violently at first. This can happen if you took one of your cats to a vet or a groomer, for example.1 Cats identify each other through smell and voice, not just by sight. A weird, unfamiliar smell signals an intruder, not a friend.

Eventually, the two cats will remember each other, but it can be pretty disturbing to watch best friends fight until they figure it out. Some people schedule vet visits at the same time to avoid this.

If you can't take them to appointments together, try rubbing the returning cat with a blanket your cats sleep on before reintroducing him to the home. Another option is to lightly rub your hands with a pleasant scent, like smelly treats or water from canned tuna, and then gently pet your kitty. The distracting but pleasant scent might overpower the vet's scent.

Fear Takes Over

Sometimes cats get scared, and this causes them to misdirect their "fight or flight" response at the wrong target. This might happen if two cats are sleeping peacefully next to each other, then hear a loud noise. Both cats get scared, jump, and puff up into defensive postures. They see each other puffed up and fear the other is attacking. This could lead to unease and fighting until they figure out they're still friends.

They're Insecure about Territories

Sometimes sudden outbursts are caused by unease about territories in the home.2 Cats are naturally territorial, but friendly cats have learned to share their space peacefully. If you recently moved to a new home, they may need to work those issues out again.

Changes in your own life can also trigger territory insecurity and stress in your cats. If you recently got married, had a baby, or even changed your work schedule significantly, your cats might be feeling a little shaken up and insecure. They could easily take that stress out on each other. When a significant change takes place, try to stick to your cats' routine as much as you can, including mealtime and bedtime. Spend extra time playing with them, so they don't feel jealous. Be patient; it might take a little time to adjust.

Your cat's territorial protection instinct can also be triggered if stray cats are outside and your cats can see or smell them. In those cases, it might be good to close the shades when feral cats are roaming, or even set up motion-activated sprinklers to encourage feral cats to visit a different yard.

Medical Issues Are at Play

If your cats aren't fixed, then sudden fighting might be caused by puberty. If they're spayed or neutered, it could be a different medical issue. Cats tend to hide health problems, but they might become withdrawn or aggressive if they're not feeling well. If the behavior persists, it may be time to take them to the vet for a checkup.

You Can Help Them

One easy and effective solution is to set up Comfort Zone Calming Diffusers in different rooms where your cats hang out. This drug-free solution mimics a cat's pheromones and helps communicate the environment is safe and secure. You might also want to try the Comfort Zone Calming Collar, especially if your cats go outdoors. This collar with the BreakAway safety feature helps keep the calming pheromones with your cats whether they're resting in the home or on the go.

You could also try adding cat trees, condos, and window perches around the house to give your kitties more territory to call their own. Tall spaces can also increase confidence and help cut down on fear-based fighting.

If the new behavior is intense, you may need to reintroduce your cats to each other. The process could take a few weeks. Start out by keeping them in separate rooms, and swap blankets and other items with their scents. Feed them on either side of a closed door. When they can eat calmly, try a closed gate where they can see each other. Then graduate to supervised visits with treats.

When cats that used to be good buddies suddenly start fighting, it's generally temporary. But sometimes they need a little help from you. A nudge in the right direction can help them remember why they love each other all over again.

1. Animal Planet. "5 Tips to Stop Cats from Fighting." animalplanet.com, http://www.animalplanet.com/pets/5-tips-to-stop-cats-from-fighting/.

2. Humane Society. "How to Help a Frightened Cat." humanesociety.org, https://www.humanesociety.org/resources/how-help-frightened-cat.