Heat Cycles in Cats

Heat Cycles in Cats
The fertile period of a female animal's reproductive cycle (the mating period) is called estrus, commonly referred to as "heat" or being "in season". The female will not mate with a male except during this period. The average female cat (queen) reaches sexual maturity at about 6 months of age. The female cat has 2-4 estrous periods every year, each lasting 15-22 days. If she is bred, estrus seldom lasts more than 4 days.

If successful mating does not occur, estrus may last for 7-10 days and recur at 15- to 21-day intervals. Estrus in cats most often occurs during the seasons of spring and fall. During these seasons, an unmated female cat may come in and out of heat continuously until she is bred.

Female cats reared indoors in the absence of a tomcat (uncastrated male cat) may not come into heat until later. Cats have an estrous period 1-6 weeks after giving birth, so a female may be nursing one litter while pregnant with another.

The period of time that she is out of heat, can vary depending on geographic and environmental factors, such as temperature and the number of daylight hours.

Mating Behavior in Queens (female cats)

Beginning at puberty, estrus in queens normally occurs about every 3 weeks between January and November. Each estrual period lasts about 1 week, with about 2 weeks between the end of one cycle and the beginning of the next. During estrus, the queen becomes increasingly restless, and may eat and sleep less. Housecats in heat may try to escape.

Since there is usually no obvious vaginal discharge or swelling of the genitals during estrus in cats, as is seen in dogs, behavioral changes are the only obvious signs that your cat is in estrus.

A cat in estrus carries her tail to one side, keeps her hindquarters elevated, exhibits "treading" movements of the hind legs, and seems unusually affectionate. She spends a good deal of time rolling on the floor and seems much more restless than usual. The cat's voice seems more piercing than usual and she may "call" for 1-2 days before she accepts the male.

The queen may vocalize excessively, sometimes crying in a loud and plaintive tone. She may roll on her back, becoming more docile and solicitous of petting or attention. She may groom herself more, frequently licking her vulva. During peak estrual behavior, the queen presents her hindquarters, elevating her hips by leaning on her forepaws with tail quivering. This behavior becomes more and more insistent. The estrual queen may display this behavior toward her owners, who may at first find it amusing. After several sleepless nights, however, they may be less entertained.

Estrus is a stressful and exhausting experience for the queen, who may eat and sleep less despite heightened levels of activity. Weight loss is not unusual during heat. Because the queen cycles so frequently, she may not have adequate time to regain lost weight before the next cycle begins. Changes in temperament, ranging from lethargy to irritability, may be observed in queens between heat cycles.

Queens advertise their reproductive status by chemical signs in urine and vaginal secretions. The scent attracts tomcats across many barriers, leading them to your home even if the queen is indoors. Immediately after mating, the queen may briefly show aggression toward the tomcat. This behavior is normal.

Unless purebred queens are intended for breeding, females should be spayed before heat cycles begin. Rather than allowing your cat to roam outdoors and possibly be injured or become pregnant, keep your cat indoors at least until it is spayed, and preferably also after it is spayed.

The signs of heat are different in cats as compared to dogs. Cats have minimal vaginal bleeding, usually not even enough to be detected. Their behavior is the most notable sign. Cats become very affectionate. They rub against their owners and furniture and constantly want attention. They roll on the floor. When stroked over the back, they will raise their rear quarters into the air, and tread with the back legs. They also become very vocal.

Until she mates or is spayed, these estrus cycles will repeat as often as every two or three weeks, causing distress to both the queen and her human companions. During these cycles, Queenie's entire focus will be on escaping the house to mate, or to mate with a male companion, if you are careless enough to have whole males in the same household. She will be single-minded in her need to mate, will loudly vocalize (call), and lurk near doors, just waiting for the chance to meet up with one of the noisy feline Romeos who will cluster near your house, fighting for the privilege of impregnating your queen.

What Happens During Estrus?

Estrus is described as the period of receptivity to mating, and is linked with the production of estrodial (a type of estrogen) produced by ovarian follicles. It is not to be confused with minstruation in human females, and you will rarely, if ever, see any signs of blood, although occasional mucous discharge may be evident.

Female cats are induced ovulators, which means that ovulation does not take place without mating or manual stimulation. If the female cat does not mate during estrus, hormonal levels will eventually drop off, and the estrus cycle will cease, until it repeats itself in another two to three weeks.

Queen's Behavior

Cats differ to other mammals, in that they don't routinely ovulate with each heat. To ovulate, they need the stimulus of the penetrating tomcat, and this is called "reflex ovulation". Most cats will experience their first heat before they are a year old. This does vary breed to breed, with Siamese often being early [5 months+] and some of the larger domestic breeds being later [Maine Coon, Norwegian Forest]. All cats, however, will display the same characteristics. They have to let the males know that they are entering estrous, and they do this is a number of ways. These are all under hormonal control, with estrogen being one of the hormones. Their urine contains more estrogen, so they are more likely to spray when in heat, to mark and let the tom know what is happening. Toms can actually tell when the queen is at peak, by the concentration of this hormone in the urine.

The most obvious indicator of impending estrous though, is the call. Queens call loud and long, and the call cannot be misinterpreted for any other reason. Some cats will howl continuously, and if you have never witnessed a cat in heat "calling" before, you may think she is actually in pain. She does this to notify any tomcat in hearing distance that she is available. How often are cats in heat? Even cats are partially under control of daylight hours, because between March and November they may call as often as twice a month, while November to March they may not call at all, or only once or twice.

You will also see her rubbing herself over everything she can, again to leave her scent. She will constantly rub up against you, and everything and anything else she can! Another thing she will do, is walk around with her body in acute lordosis, [see photograph below], which is her position of breeding. Anything that brushes up against her, she will turn so that she presents herself for breeding.

If queens are allowed to continually go through heat cycles, she is at risk for PYOMETRA, which is both serious and can be fatal.

Pyometra is a serious infection of the uterus, in unspayed or whole females. It is an abscess of the uterus, seen in whole queens, and can be open or closed. Rarely, it can also be seen in queens who had a piece of their cervix left after a spay. It occurs in females who are sexually mature, and so can be prevented by spaying them as early as possible.

The queen shows signs of serious illness. The build up of pus in the uterus makes the abdomen look and feel distended and firm to touch. The only difference between the open and closed types is that in the open one, the pus can seep out of the uterus and be seen at the introitus, or vaginal opening. The cat becomes quite toxic because of the toxins released from the accumulated pus. The cat will likely have a high fever, resulting in increased thirst and urination, and occasionally vomiting. They are often lethargic, as movement causes more pain, and are frequently depressed. They also have a decreased appetite. The books don't seem to be in agreement as to which age group of cats is most at risk. The one thing they do agree on, is that it starts as a chronic endometritis, which is a thickening of the uterine wall, resulting in a hormonal imbalance, and is a common cause of feline infertility. It always follows a heat cycle, showing signs 2-8 weeks after the cat comes out of estrus. In some cats, it can be missed if the owner is not aware of the possibility, because occasionally the only sign of problems is lethargy. The combination of a distended abdomen and signs of acute illness following estrus, should be dealt with immediately. Most sources say that cats who have never been bred are in the higher risk group. You should seek veterinarian care immediately.


Previously, the only treatment was to immediately remove the uterus and put the cat on covering antibiotics. If the cat is not part of a breeding program, this is the route I would take, as it saves lives, especially if done before the queen becomes toxic. However, today's vets often take the less drastic measures of giving the queen intravenous [or intramuscular] antibiotics, supportive I.V. fluids and fairly intensive care. More and more queens are recovering, and are able to reproduce providing there is no scarring, which is an unfortunate complication of intra-abdominal infection. So, if the queen is to be bred, and you don't get a satisfactory mating after several tries, it is likely because the infection scarred to fallopian tubes too much. To alleviate any possibility that YOUR cat may suffer with this problem, please spay you cat as soon as possible, preferably before she slips in to her first estrus, or heat.