If 100% of the domestic cats in North America were spayed and neutered at all times, within a generation there would be no domestic cats on the continent. They’d only be feral and stray cats. I think that is an interesting thought (note: in practice there would be pedigree cats left as breeders are excluded from spaying and neutering obligations).
The call for much more neutering of domestic cats is sensible because there is still a good proportion of cat owners who don’t sterilise their cats or they spay their female cat after she has had a litter. The pressure should be maintained on increased spaying and neutering.
However, if the ultimate goal is 100% sterilised domestic cats, it is undesirable. If at the same time all cats: domestic, stray and feral were successfully sterilised, there would no cats in North America in a relatively short space of time. There would be an outcry.
What might happen in the future, if people get it right, is that spaying and neutering of cats will reach a level at less than 100% but a point where a supply of domestic cats is maintained such that they are all wanted. But there may be distribution problems.
What if California is extremely effective at spay/neuter programs. Let’s say it becomes obligatory by law and all cats have to be registered. In time, there would be no kittens in California so when cats died of old age there would be no cats to replace them. They’d have to be shipped in from a neighboring state.
In a crude sense, effective mass sterilisation causes a species to become extinct. The biggest problem with the wild cat species such as the Siberian tiger is that they don’t reproduce enough. The tigers have become sterile due to inbreeding. This is the biggest danger to extinction of a species with a very small population (400 or so for the Siberian tiger).
The statements I am making are theoretical because there will always be people who allow their cats to breed. At present this is a major problem in some countries, which is why laws are being introduced to make registration and sterilization obligatory.
However, an eye should be kept on the long term objectives. If it is overdone, it may cause unforeseen consequences.
Another consequence of mass sterilisation of the domestic cat while sterilisation of the feral cat is less effective is that we are left with a greater proportion of feral cats compared to domestic cats.
Also the character of a cat is partly due to his/her genes. If we sterilise all the cats with good genes that make the cat friendly and therefore an excellent companion, we are reducing the pool of the best companion cats .
Once again this is more theoretical than practical. However it is an interesting concept.
Putting it crudely, I have always said that it is about supply and demand. Just like humans, there has to be some reproduction of cats to maintain supply. Some countries such as Germany have an increased population of older people who are unproductive economically. There is not enough breeding of humans!
What conclusion can I draw from these thoughts? Spaying and neutering should be increased but not to near 100%. You could argue that the best cats – whatever that means – should not be sterilized. That would be social engineering and very unwelcome, but theoretically it would be sensible. This is all a long way off and will never come about. At the moment the problem is not too much spaying and neutering but too little.