Question from Kelsey,

I have 4 cats in my home, 3 females and 1 male.  Buddy, my male, is generally a very gentle, loving cat, and sort of took my baby cat, Valentine, who is 10 months old, under his wing when she came to live with us; she pretty much shadows  him everywhere he goes.  Recently, Valentine escaped the house and was gone for about three days.  She has since returned home safely, albeit a little timid and dusty, but none the worse for wear.  However, Buddy acts like he’s never seen her and is very hostile.  I thought at first it was because she didn’t smell right to him, but he doesn’t show any signs of lightening up on her.  He hisses and bats at her, growls if she walks by, and won’t let her look out the back door with him and Ceci like they’ve always done together.  She’s confused by his behavior and sticks close to my side so Mama can protect her.  Is there anything I can do, or is this something that will resolve over time?  And if it’s a time thing, about how long will that be?  Thank you!

Answer from Amy:

Cat aggression can be enigmatic. There are numerous reasons why cats become aggressive. It can stem from stress, illness or various uncertainties. When a cat’s behavior shifts south, it can affect other cats, animals and humans in the same household.

There are several possibilities to your cat’s aggression. However, let’s first look at a few common types of aggressive behaviors in cats:

Territorial Aggression:

Cats become territorial when sharing a house with other cats. Each cat demands for a personal space or sanctuary where they can attain their domain. However, in a crowded area, trespassing another cat’s territory is inevitable which can be irritating to the cat and causing the cat to act aggressively. Spraying is the most common form of territorial marking among cats. Even neutered or spayed cats can spray or leave their mark to show other cats this is their personal area.

Unfamiliar Scent Caused Aggression:

It is true that when you bring in a new kitten or cat, the established cat can become aggressive, unease and stressed. The change of behavior is usually accompanied by spraying, growling, hissing, chasing or/and swatting. The reason of doing so is to establish the cat’s social status in the family. In a cat colony, there is a clear hierarchy structure where the alpha cat is usually the most confident cat in the crowd who likes to stand tall and centered. The submissive cats are usually found along the perimeter of the colony, timid and constantly watch out for their safety.

In order to solve territorial issues in the house, a very effective way is to