Initially, when a cat or kitten is newly adopted to a home, it is more likely to be wary or quite during the first few days of its stay. Some cats would even spend their first few days hiding. This is because they are trying to get used to their owner and the new environment where they find themselves.
Sometimes when members of the household try to press their attentions on the newcomer, a few cats would become defensive and can begin to swipe or even hiss at them. This is not a hard-and-fast rule; as a temporal effect, early wariness is a normal thing.
Instead of having a fearful kitten around, most cat owners would prefer to have a friendly lap cat that is happy and agile. To this end, most owners would not worry themselves if their cats are feral being tamed. Before being released as working cats, some of these felines were initially feral that were made accustomed to their new environment.
When a cat perceives it is under a threat – especially that from which it is difficult to escape – an uncommon behavior can be displayed. This weird behavior is known as defensive aggression. This type of aggression is commonly recognized by the cat’s typical body postures that come along with it. Some of these reactions include hissing and spitting, crouching, standing up of hair (piloerection) and crouching.
These are common signals that they display whenever there is a further approach from another animal or person. It is only when the defensively aggressive cat is approached that it will attack. Although these felines may not have the intention of fighting but if the threat continues to come any closer, they will do so in self-defense.
Like the cat in the video, it is not far from being a defensively aggressive cat. Its action towards the stranger bear who came visiting the home uninvited explains it all. Cats are have this instincts of being distrustful to anyone who is not part of the family. This cat here had taken time to observe the movement of the curious bear through the glass. Even when it tried to manipulate the door handle, the cat waited patiently for its next action and without any further ado, it launched its defensive attack when the bear advanced further.