Why does this happen?
This is fairly common and is termed Non-Recognition Aggression, cats rely on scent to recognize each other. Her visit to the hospital has changed her scent to the point where her brother can no longer recognize. A few theories behind it are:
- The cat expressed his/her anal glands or is emitting pheromones associated with stress.
- The cat took home scents of other animals who were previously at the clinic
What to do?
It is a good idea to keep them separated in the meantime for each others protection. A few things that can help:
- Giving blankets with each others scent to opposite cats (i.e brothers blanket goes with sister and vice-versa)
- Feliway Friends
After 24 hours try to gradually re-introduce them, either by opening the door a crack for them to sniff or to have a gate in between. It does self-resolve after some time you just need to make sure the conflict is over before putting them in the same room.
How can I prevent this?
Next time, if possible, bring both cats to the hospital - they won't lose sight of each other.
After their sterilization surgies. It took the female cat, one week to get back to normal. She was so mad at her brother. IT's hard and annoying, but remain calm and let them be. They will come to terms.
Don't call them "BAD" or shout at them. Let them be
– Hani Gotc Aug 23 '21 at 08:55