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A common question that we receive at the clinic is "How often do cats go into heat?" The short of the answer is usually every 2 weeks during the longer light days, or the mating season, which typically begins late January and to February and early spring. In this article, I'll review the details of the female cat's heat cycle, and hopefully answer your questions along the way.
A heat or estrus cycle in animals is made up of different stages. They include proestrus, estrus, diestrus and anestrus. During the longer days, cats go through these stages very quickly, often within 2-3 weeks.
What is interesting about female cats is that they have a polyestrous cycle and are considered "long-day" breeders. This means their estrous or heat cycle is stimulated by light, so the more and longer duration of light they are exposed to, the quicker or more rapidly they will go into heat.
Additionally, cats are induced ovulators. The act of mating will cause the release of eggs from the ovary, and during the breeding season, they cycle repeatedly until pregnancy or pseudopregnancy occurs.
As we have discussed, the breeding season in cats is related to the length of daylight throughout the year.
In the northern hemisphere, female cats will start their reproductive cycle mid to late winter, which coincides with the lengthening of daylight hours. The peak season for a cat's heat cycle is around February to April, but it can continue all summer, depending on the cat's location and the degree of daylight.
As a general rule, 12-14 hours of exposure to daylight will stimulate the reproductive cycle in female cats.
Generally speaking, the first heat cycle in cats occurs around 6-7 months of age; however, I have seen it happen as early as 4 months of age and as late as 12 months of age.
During the estrous cycle, cats have the "estrus" or heat period, which can last anywhere from 4 to 14 days. During this period, she will be very vocal and attract attention from intact male cats.
If the female cat, or queen, doesn't breed while she is in heat, she will go into diestrus, which is the phase after estrus or heat. Provided that there are long daylight hours, she will quickly go back into heat and start the cycle again. Her entire cycle can repeat every 2-3 weeks.
Mating will result in the release of eggs from the ovary, which often results in pregnancy. If the queen ovulates and the eggs are not fertilized, then she can enter pseudopregnancy for 40-50 days. Pseudopregnancy can closely resemble pregnancy, with the difference being that there are no kittens.
Cats in heat commonly reveal the following signs:
If you notice that your cat is showing signs of heat and you do not wish to breed her, it is best to keep her indoors and away from male cats. Depending on her perseverance, she may attempt to escape when doors or windows are opened.
If you have an intact, non-spayed cat that is not a breeding queen, I strongly advise considering spaying. Spaying reduces many risks, both behavioural and medical, such as mammary and ovarian cancer, as well as life-threatening uterine infections (pyometra).
A cat will be pregnant for around 64-66 days. As she nears the end of her term, you will notice signs of labor, and it is important to recognize this so that you can prepare for queening.
If you are unsure if your cat is pregnant or would like to know how many kittens are present, an X-ray can be done after 40 days. This timing aligns with when the kittens' skeletons start to calcify and are visible on X-rays.
Ultrasound is another good option and can be performed early that X-rays, around 10-15 days.
