The so-called heat of a female cat is seasonally polyoestric. Several oestrus phases occur consecutively and are limited to certain seasons. With the onset of sexual maturity (puberty), the first signs of the heat begin. This varies from cat to cat and also from breed to breed, on average however between 7 and 10 months and depends on the light conditions and the weight (with approx. 2.5 kg). This means that at least 12 hours of sunlight a day must be present over a period of 24 hours in order to maintain a heat. Accordingly, there is no rutting season between September and January. Pure domestic cats that may be exposed to artificial light may show signs of heat throughout the year. How a typical cycle works, is explained afterwards.
The phases of the cycle
The so-called proestrus, is the first phase of the heat and lasts on average 1 to 2 days. Due to the prolonged exposure to light in spring and the resulting release of the follicle stimulating hormone, egg maturation in the follicles is stimulated and the oestrogen level increases. It is important to mention that the female is not yet ready for mating in this part of the cycle, but she is very interesting for mating males. The behaviour shows that the cat begins to lift up its rear end, rub its head and body more against objects or persons and its upright tail waggles restlessly from left to right. Loud meowing and possible marking of objects are further signs.
In the actual heat, the oestrus, the female cat is now ready to mate, the phase lasts about 3 to 16 days. During this time the oestrogen level reaches its peak and the she is ready to get prgnant from this time on. Up to 12 eggs are formed.
The heat ends only after ovulation. In order for this to occur, a mating is usually necessary (induced ovulation/provoked ovulation). If the female cat is covered by different males, the puppies from the litter can have different fathers. Thats amazing, isn`t it?
If no copulation has taken place during this time, the so-called interestrus follows, which is initiated immediately after the oestrus phase and lasts between 3 and 14 days. In this phase, the follicles recede and the oestrogen level drops. If the oestrus cycles merge into each other and thus the interestrus is skipped, you can speak of continuous heat. In this case, the oestrogen level hardly drops and the female cat shows continuous signs of a heat.
In the intermediate heat, the di-oestrus, the uterus allows the fertilized egg to implant itself and the signs of a boldness disappear. Regardless of whether the female cat has become pregnant or not, the corpus luteum in the ovaries produces the hormone progesterone. The progesterone level is now highest. The degradation of these corpus luteum hormones can take up to 12 weeks (luteolysis). The sinking progesterone level can now lead to an increased release of the hormone prolactin, which boosts the milk production of the female cat. This can have the consequence that it can come with some females to a false pregnancy.
The last phase is called the resting phase (anestrus), in which the female does not show any signs of heat and lasts on average 45 to 160 days. The phase again depends on the light influences and usually takes place in the autumn and winter months when the daylight exposure does not exceed eight hours.
Like all female mammals, female cats have a sexual cycle. With the sexually mature, they become heat for the first time and can become pregnant. The heat is divided into four phases and may vary in duration and frequency from breed to breed.