Why does my male cat 9 months old attacks female 13 year both fixed?

1. Redirection of aggression: Sometimes, cats may redirect aggression towards another cat if they are feeling stressed or anxious about something else in their environment. This could be due to changes in the household, such as a new person or pet, or it could be a response to outdoor stressors, such as unfamiliar cats or loud noises.

2. Territorial behavior: Male cats may display territorial behavior towards other cats, even if they are fixed. This is because male cats naturally have a larger territory than females and may feel threatened if another cat is perceived to be encroaching on their territory.

3. Dominance: Some male cats may display dominant behavior towards other cats, trying to establish their authority. This can be especially true if the younger male cat feels threatened by the older female cat's status in the household.

4. Playful aggression: Kittens and young cats often engage in playful aggression, which can sometimes be mistaken for actual aggression. While playful aggression is usually harmless, it can still be stressful for the older female cat.

5. Underlying medical issues: In some cases, aggression can be a sign of an underlying medical condition, such as pain or discomfort. If your cats' behavior changes suddenly, it's always best to have them checked by a veterinarian to rule out any potential health issues.

To address this issue, you can try the following:

1. Redirect the attention of the younger male cat when he shows aggression towards the older female cat. This could involve offering him a toy or treat to distract him or redirecting him to a different activity.

2. Create separate spaces for the cats. This could involve providing them with separate litter boxes, food bowls, and sleeping areas. This can help to reduce territorial conflicts and give the older female cat a safe place to retreat to.

3. Encourage positive interactions. Try to encourage positive interactions between the cats by providing them with opportunities to play and interact together. This could involve using interactive toys or treats to encourage them to play together.

4. Discourage negative interactions. If the younger male cat does show aggression towards the older female cat, be sure to discourage this behavior by firmly saying "no" or by clapping your hands. You can also try to physically separate the cats if necessary.

5. Consult a veterinarian or animal behaviorist. If the aggression persists, it may be helpful to consult with a veterinarian or animal behaviorist to get further advice and guidance on how to manage the situation.