Why are my cats fighting, staring aggressively with puffed tails?

This sounds like a typical play behavior. In general watch for signs that one cat is trying to avoid the other cat. Watch for the cats hissing at each other. Watch for any signs of intentional bites or scratches that leave marks. If the cats are willingly interacting and you don’t notice any hiding or avoidance behaviors, this is likely consensual play. You may also look into reading a few books about cat behavior as it is not only informative but also fun! I hope this helps.

If only pets could talk! Cats can be very reactive and can also get frustrated easily. It’s possible they saw another cat out the window and are reacting. You may try to separate them for a few hours. Keep the environment calm and check on them frequently to make sure they are not agitated. You want want to close the blinds to block out any views of the other cat. If the behavior continues, have them examined by the veterinarian. I hope this helps and please feel free to post any additional questions.

Cats, like people , especially siblings, do get into tiffs at times and fur flies.....this is quite normal and nothing to worry about. I have 5 cats and one or another fights here and there and the next day you see them lying next to each other. Unless one mobs the other constantly, the occasional tiff is nothing to worry about

Yes, it all sounds very normal! I would continue to supervise their interactions for a few more weeks, but it sounds like they are getting used to each other. Unless they start fighting a lot, I wouldn't recommend trying to distract either of them while interacting since it could cause them to be annoyed with you or cause one of them to get hurt while being distracted.

While it's fine that they growl and hiss at each other, as they are letting this new cat know they don't appreciate his presence on their territory, you don't want it to escalate into aggression and one of your cats get injured. I would keep an eye on their interactions as best you can, and step in if it appears that anyone is going to get aggressive.

It may be due to illness or injury. It can also be redirected (or displaced) aggression. This is when one cat is unable to directly respond to a perceived threat and "vents" on whoever is closest. This is usually an owner or another pet. Never handle or grab your cat if she is displaying aggressive tendencies. This can lead to a serious bite or scratch. Schedule an exam with your vet to rule out medical causes. If they are indoor cats, provide a ' cool down' period by separating them. Keep stray or strange cats away from windows or doors and out of your yard. Control what your cat sees by closing doors or drawing the blinds. Consider using pheromone products to decrease anxiety/stress level in the house. Search www.pet360.com for pheromone products.

It sounds like Oreo and Bliss get annoyed with each other at times. Just like humans, cats can become annoyed with their companion's company, and react with aggression. I have four cats, and while they typically get along really well with each other, occasionally they have spats where they get grumpy with each other. It's normal cat behavior, and not something to worry about :-)