My cat Shadow is always swiping or hissing at my cat Marley

by Anonymous

I have two cats, Marley (female) who is about 4 years old. Then I have Shadow (male) who is about 9 and a half years old. I’ve had them both all their lives, and they are okay in the summertime. But in the winter and fall, Shadow is aggressive with Marley. When he walks by her or when she walks by him, he hisses and tries to swipe at her. Any advice on what to do? Is this normal?