Like most female mammals, cats go through physical cycles that prepare their bodies for fertilization and birth. In humans, this cycle is called "menstruation." In felines, it is called "estrus."
When female cats are experiencing estrus they are said to be "in heat" and are hormonally receptive to both intercourse and reproduction. Cats can go into heat in late kittenhood, making it necessary to spay them if a pregnancy, and the responsibility of raising and finding good homes for kittens, is unwanted.
Heat Cycles in Cats
Cats are polyestrous, which means heat cycles happen periodically during their fertile years. These cycles may start as early as four-months-old and will continue until a cat is either bred or spayed. Heat cycles in cats can last several days, up to two weeks, and repeat themselves every two to three weeks. It's easy to see, then, how a female cat almost always seems to be in heat. Many veterinarians practice early spay and neuter for this reason.
When your cat is in heat, it's a noticeable event. And while it's hard to prove that heat cycles aren't painful, the calling (or loud howling) she exhibits make her seem uncomfortable. However, a female cat's howling has a purpose—to attract the attention of a potential suitor. Recognizing this fact eases your worry about something being wrong, or "off," with your pet.
Timing Is Everything
With the arrival of spring, a female cat in her sexual prime will begin a heat cycle. The longer days, filled with warmth and sunlight, trigger your queen's body to come into season. This heat cycle usually lasts between a week and ten days. Then, if a pregnancy isn't achieved, she may go back into heat a few weeks later and continue this pattern until she becomes pregnant. If she mates during this time and becomes pregnant, she will go back into heat approximately eight weeks after the kittens are born, or just after they wean. But if your cat mates and doesn't get pregnant, a false pregnancy may ensue where she exhibits the signs of pregnancy briefly, before going back into estrus four to six weeks later.
What Is "Heat" Like for Cats
While it's logical to assume that a cat in heat will have the same physical symptoms as a woman having her period, the reality is very different. First, cats do not shed the lining of their uterus. So contrary to popular belief, heat should not involve vaginal bleeding. If your female cat is bleeding, contact your vet. Since human females shed the lining of their uterus every month, cramping, bloating, and related symptoms can be present. Cats do not experience cramps or other physical symptoms, despite their howling and need for attention during this time. Instead, a surge of hormones will make your cat extraordinarily eager to mate. She may rub against you, pace back and forth, and assume a mating position if you pet or stroke her. You may notice your cat loses her appetite during this period, as well, or she may lick her genitals often and mark her territory by spraying. She may also attempt to run out the door, escaping to find a mate. This is all normal behavior during heat.
How to Manage a Cat in Heat
A cat in heat is incredibly difficult to live with. And because your cat's behavior is absolutely normal, don't try to search for a "cure." Yes, it is possible to use vet-prescribed synthetic progesterone injections to ward off heat and save both your cat and yourself from its symptoms. But frankly, spaying is a better choice and a more permanent option.
If you do intend to breed her and just need to get through these cycles, provide your cat with toys or pillows that she can shred while she's in heat, and play with her often. Make her a nest with a warm heating pad for privacy and offer her catnip to calm her down. If things seem to escalate and she becomes troublesome, stress-relieving herbs, made especially for pets and found at your local health food store, might work as a last resort.