Tomcats can’t, it seems, tell the difference between females who have been spayed and those that have not been spayed. This information comes from Dr. John Bradshaw in his book Cat Sense It is based upon his admittedly “casual observations”. He writes that “tomcats seem unable to distinguish between neutered females that form the large majority in many towns and cities, and a few, mostly young, females that are still reproductively intact”.
He writes that roaming tomcats still visited his home on a yearly basis in late winter to check out his two females. This occurred even 10 years after they had been spayed. His two females had produced one and three litters respectively.
He believes that spayed females are difficult to distinguish, from a tomcat’s standpoint, from intact females between seasons. They can’t tell the difference from the way they behave and the possibly can’t even tell the difference by their odour to which tomcats are very sensitive.
As a consequence, tomcats are at a massive disadvantage nowadays. They are surrounded by spayed females. Even feral cats are often spayed and neutered under TNR programs. There has been a big push to sterilise all domestic and stray cats in developed countries particularly America and the UK. There’s been great success in this objective. Bradshaw says that they face a “needle-in-a-haystack problem”. Only a few of the females that they interact with will ever be able to sire their kittens.
They therefore have to roam as widely as possible. They strain their senses to pick up the sound of the female yowl and the distinctive odour of a female who is coming into season.
The urban, unsterilised (unneutered) tomcat is unlikely, therefore, to locate reproductive females to defend in his harem. Where there are tomcats it appears that they roam around like their wildcat ancestors hoping to bump into a young female who has not been spayed.
Some owners delay the spraying of their female cats in order to allow them to have a litter. They believe that it improves the character of the animal. This is a misapprehension. And sometimes domestic cat owners are unaware that their female cats can be sexually active and come into season when they are as young as six months old. Bradshaw puts down to modern day nutrition which is superior to days gone by and which enables females to mature more quickly than before.