First oestrus/season

Oestrus or coming into season signals the beginning of sexual maturity and means your cat can now become pregnant.

Cats usually have their first oestrus between 4 and 12 months of age. The main determining factors that bring on the first oestrus are day length and body weight

Cats will often come into season for the first time when they have attained 60-70% of their adult body weight.

Some kittens born in summer will come in season late that winter or early spring as the day length increases, and they have attained an adequate weight. Some winter born kittens may not come into season until the following late winter/spring as by the time they have grown sufficiently the day length is shortening. However, there are no rules without exceptions, and some kittens  may actually come in season once they have attained the necessary body weight regardless of the time of year.

Some larger breeds or long haired breeds can tend to be later having their first season.

Reproductive cycle of sexually mature cats

Cats are what is known as seasonally polyoestrous. That means they have a breeding season during which time they will come in season repeatedly. The reproductive period usually spans late winter/early spring until early autumn and once sexually mature they may come in season every 3 weeks or so. (Most reproductive behaviour will occur between February and October)

Female cats when in season will change their behaviour noticeably.

They may become more affectionate and require more attention than usual, they will rub themselves against furniture or their owners, they will roll around on the floor, they often become very vocal and will adopt a position with their abdomen low to the ground with the tail held in the air. 

This strange position accompanied by loud crying can often lead owners to think their cat has injured itself.

Cats may even spray urine onto upright objects in the home.

Spaying/neutering will prevent cats coming in season and prevent pregnancy. Spaying is often best done before a kitten is due to come in season, ask your vet about specific timing.

Cats will mate with any male (including male littermates) at the first season and may become pregnant, with mating only lasting a minute or so. If a cat becomes pregnant after mating she will stop coming into season and these behaviours will cease until her cycle begins again some weeks after the kittens are born.

Unwanted pregnancies due to delayed neutering are a very common problem and it can be difficult to find nice homes for the kittens. Therefore, if you have no intention of breeding from your kitten later, you should speak to your vet to arrange for your kitten to be spayed before she is 4 months old.