Hi Lisa,
Thanks for your question. I love this type of question as much as I am frustrated by it.
Let me start by saying that I won’t be able to answer this question. There is so little information in the question, but more importantly, your cat requires a physical examination in order to understand why he crouches. My recommendation would be to see your veterinarian and have him or her perform a physical exam paying particular attention to the spine, joints, limbs, jaw, abdominal cavity, oral cavity, and consider imaging like X-rays. This is a list of areas that may be experiencing pain that can cause an animal to crouch as you describe.
The problem with a question like this as well is that this could just be the personality of your cat that is causing the crouching. The most important thing to recognize is how long has it been going on? If the cat crouching developed recently, then it’s more likely to be a medical issue that is causing pain rather than a behavioral issue. I’d recommend you create a video of this behavior to show to your veterinarian. After working with animals so long, there are subtle things that I can pick up on in a video where they’re doing something like this at home but won’t do it in the exam room.
Hopefully, this is a good start for you. Best of luck.
Dr. Clayton Greenway