why has my 13yr old cat become aggresive?

my 13 year old cat does not seem to recognize my 11 yr old cat although they have lived together for 10 yrs.she is now extremely aggressive towards her and doesn't want her in the house.this has not happened before to this extent.she is happy enough when she is on her own.im not sure wat could have changed?

Answer by Kate
Hi
Most cat aggression is caused by fear as you know. This change in behavior towards another cat is a common problem and is known as trauma aggression. basically something has frightened your cat, now it may have had nothing at all to do with your other cat but the fear has been transferred or blamed on them. this is common.

the initial fear could have been caused by absolutely anything, from a strange smell, loud noise or getting their tail caught somewhere, it doesn't really matter what the cause was.

What is need is a period of time where the two cats can rebuild there confidence in each other in a safe environment. For this i recommend that you go through a period of introduction training again described on this page

https://www.our-happy-cat.com/introducing-cats.html

it does take a little time and effort but is helpful to the cats and should allow them to be friends again

best wishes Kate

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