cat suddenly attacks sibling

4 cat household and everyone getting along suddenly 1 cat out of the blue attacks her sister. This went on during the night and I had to separate them. any advice

RESPONSE:

Since this sounds like an unusual, 1 time event, don't worry about it and don't intervene. Just let them work it out on their own. Cats often start this kind of activity because they are bored. Play with them before bed so they will be tired if the behavior continues otherwise, don't worry about it. It's normal.

Donna - House Full Cats Mom