Why does cats raise their fur when they are scared?
There are several different reasons why a cat fluffs up his
tail.
When a cat is in a confrontation situation, he will fluff up his
tail - and the fur on his entire body also. What he is in fact
doing is trying to make himself look "bigger" in front of his
opponent.
If a cat's tail is lowered but fluffed up and he is adopting a
crouched kind of position, this generally indicates that he is
frightened of his opponent and does not want to enter into any kind
of confrontation.
Sometimes when a cat is in a playful mood he will fluff up his
tail, but in this instance you will notice the tail is in an
upright position and he generally will not give the appearance of
being frightened.