When do domestic cats reach maturity? I have to say that I normally rely on reference books for this sort of question together with my personal observations. My reference books are letting me down and therefore I have make up my own mind as to when domestic cats stop growing.
I would like initially to work backwards from humans. Both humans and domestic cats are mammals. They have a similar physiology. Might it be reasonable to argue that both humans and domestic cats stop growing had a similar point in their lifespan? If that is a reasonable suggestion, human males stop growing at about 20% of their lifespan.
The mean lifespan of a domestic cat is probably about 15 years. I know a lot of people will say that’s too short and I also know that a lot of domestic cats live to up to 20 years old. But let’s take 15 years of the average domestic cat lifespan. 20% of 15 makes 3. Therefore on this calculation you could say that domestic cats stop growing at the age of 3.
Observing my cat I think he reached maturity at somewhere near 2 years of age and perhaps a bit older. It is very hard to decide precisely because although a domestic cat observably reaches a terminal size they may keep on developing such as building muscle which you might not notice.
For example, wild tigers are still developing muscle at the age of 5. And some purebred cats such as the Maine Coon are said to reach maturity at about the age of 4. I can’t see a logical reason as to why Maine Coons should take longer to reach maturity than a standard domestic cat. Perhaps it is to do with their size which may be a reasonable argument.
Some people say that domestic cats reach maturity at about 12 months of age. If you refer to the domestic cat’s wild ancestor, the North African wildcat, which is always a good idea because you can find answers there, they become independent and about 1 year of age. But being independent does not mean they have matured. It means that they are able to survive as sub-adults. But the information points to full adulthood not long after perhaps at around 18 months.
I’m going to conclude that domestic cats stop growing at about 18 months of age to 3 years of age. There may be a variation between individuals and between the genders. This is a very imprecise answer but it is the best I can provide at this stage. I would love somebody to provide me with an accurate answer in a comment, please.
Postscript: for the sake of completeness, I have failed to find a scientific study on this topic. We need some science and as I said at the beginning the best books I have don’t help me with accurate data.