Why is my cat suddenly needy, aggressive, biting, and hissing?

A sudden change in behavior from the normal can be a sign of illness in a cat. Given that Ava is acting very differently from the way she was before, I'd take her into a vet today for a health check. Best of luck.

Thanks for using Petco Pet Education Center, formerly Petcoach. By far the most common cause of biting in cats is anxiety. Has anything in her life changed recently? New person or pet in the house? New routine? Did you move? Painters or construction in or around your home? And sometimes we can never identify a cause. If she is an indoor cat, it is unlikely to be infectious in nature. Try the following which are all shown to reduce anxiety in cats. If these do not help, talk to your vet about prescription behavior modification medications that can help.

 -Feliway- calming cat pheromone- comes in many forms from pet stores or online. 

- Adding a litter box. Studies show that the ideal number of litter boxes for a home is #of cats +1 . This is regardless of how clean you keep his current litter box.

 - making sure she has plenty of “high space”. The safest (and therefore least anxiety-inducing) place for a cat is UP. If you don’t already, get a cat tree or put up a shelf or two that she can go perch on. Best wishes to you and Mitzi!

Sudden behavioral changes can sometimes indicate pain or an underlying illness, so if this came on suddenly a vet visit is always a good first step to rule out any health problems. If your kitty is in good health, looking for something that may have triggered it such as a new object, new people, possession over toys etc may help you understand what caused it. Stress can make cats act uncomfortable or unpredictable, so removing the stressors or making it so your cat has a place to escape and relax may help him feel better. Pheromone diffusers/collars can also be useful in dealing with stress and aggression, and placing one on your cat or plugged into the area where he is being territorial may help him calm down.

It's possible the stress of your being gone caused the behavior change. I would give Hippy a few days to rest, relax, and make sure she can get to her food, litter, places to hide, etc without being bothered and see if that helps. Sometimes, pain or underlying illness can also cause a cat to suddenly lash out and hiss or swat at other cats, so if the behavior continues or you see visible signs of illness, a vet visit to rule out health issues is best.

Thank you for contacting Petco Pet Education Center, formerly Petcoach with your question about Brett. She is a beautiful girl! I'm wondering if the move has caused this change in behavior. Moving is very stressful for a cat, and that can lead to aggression. I'd try using Feliway diffusers around the home. These release calming pheromones that can help relax her. I'd pair that with a Sentry calming collar. This will release calming pheromones when in contact with her skin. If this doesn't help, then I'd have her seen by a vet for a health check. I hope this helps!

I'm sorry you are facing this frustrating problem. I would recommend that you take the one who is suddenly being "grumpy" to the vet. Sometimes if they are painful or not feeling well, they will become more irritable. You can try temporarily separating them again, or separating them for at least part of the day so that the "victim" has a "safe zone" or some time where he or she feels safe. But the sudden onset of the change in behavior does concern me that something may be going on with the one who is acting more aggressive. Best of luck, thank you for asking Petco Pet Education Center, formerly Petcoach.

Since it sounds like this is a recent behavior change for Zora, I would be very suspicious that she may have an underlying medical problem causing her aggressive behavior. There are a number of common problems in older cats that can cause behavior changes like this, including hyperthyroidism, chronic kidney disease, or even pain from arthritis. I would recommend taking Zora to the vet for an exam when you are able to - he/she can do blood work if needed to check for these issues. If a problem is found, it's likely that it can be treated with medication to make her more comfortable and hopefully improve her mood as well :)