You can often the tell the sex of a cat from their face. Sometimes, it can more difficult to tell the sex of a cat when you try to check the rear end. For me, this is because the anatomy at the back end of a male cat, after he is neutered, is not hugely different to a female’s when you are only allowed a glimpse. The fur hides stuff too (but see Gunner, Sphynx cat picture). And it is a little tricky to get a cat to keep still long enough to assess the area thoroughly. And why should it be easy? So undignified. Cats don’t like you fiddling around that area and rightly so.
However, neutering not only changes the configuration of the rear end of a cat it can also change the front end (I say). If you see a genuine unneutered, stray, male cat, they have an aura about them that shouts, “male” watch out. They are more jowly around the face (squarer faces with cheeks). And, in any case, you can see his b*lls. Sorry to be rude but they are obvious. The removal of interior of the male cat’s testicles is the sole reason why sexing a cat can be a bit tricky. Sometimes it is obvious, though.
Note: The best book on cat health care says that if neutering a male cat takes place at 6-7 months of age “growth and bone structure are not adversely affected..”. If done at 7 weeks of age the male cat becomes taller and can’t “extrude the penis”. I think it can make the male face look slightly more feminine. I am referring to the jowly, solid appearance of a unfixed cat. This is not a scientific statement.
The other effect that masks the differences between male and female cat faces is that, as for people, there is a wide range of femininity and masculinity in facial appearance. At the far end of the spectrum a male cat screams, “I am male” and, likewise, for a sweet faced female cat who purrs, “I am a girly girl cat”. There are lots of cats who occupy the middle ground where things get less clear cut.
However, all that said, sexing a cat using facial features combined with a glimpse of the rear end should produce a fairly high success rate. The picture shows four cats, two females and two males, almost selected at random, which demonstrates the clear difference between female and male faces.
Note: Obviously it you are a veterinarian and you have a submissive cat on the table allowing you to make a thorough inspection of a cat’s anatomy, you’ll be able to achieve a 100% success rate on sexing a cat. What I am writing out is seeing a cat and making a decision from a fairly casual glance.
A couple of stray cats come to my home. I still feed them. The owner says they are both males – brothers. I think they are brother and sister! I am going on gut feel and facial appearance. Also the female cat has a slightly girly voice. Their rear ends don’t help me much although there is not a vestige of testicles on the cat I say is female. Castration leaves small bumps of fur.