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A Cat's Menstrual (Heat) Cycle

Source: PetWave, Updated on July 16, 2015

Reproductive Maturity

Female cats, appropriately known as “queens,” vary quite a bit in the age at which they first reach reproductive maturity. Some may have their first heat cycle as early as 5 or 6 months of age, especially the Siamese and related short-haired Asian breeds. Other breeds, including the longer-haired varieties such as the Persians and Himalayans, are typically not sexually mature until they reach 10 to 12 months of age, or even older. The full estrous cycle (of which the “heat” is one phase) may last as little as 4 days, or as long as 30 days, with the average being about 6 days, give or take a few. In a typical cat, puberty occurs at around 8 to 9 months of age. Longhaired cats usually start their cycle later than their shorthaired cousins.

Estrus Cycle

There are four distinct phases of a cat’s estrus cycle. There is a great deal of individual variation in the length of each of these phases, which makes it difficult to determine exactly when a queen is ready to conceive. The four stages of the cat’s estrus cycle are: proestrus, estrus, interestrus and anestrus. They are, in a nutshell:

Stage 1

Proesterus: This is the first stage of “being in heat.” Proesterus lasts about 1 to 2 days. The queen’s vulva may be slightly swollen and moist during this phase. She also may have an increased appetite and be a bit restless. Males are interested in her, but she is not interested in them.

Stage 2

Estrus: This is the second stage of a queen’s heat cycle. This is the period when sexual reproduction occurs, and is what breeders refer to as “being in heat.” Estrus lasts about 4 to 10 days, and is the time when a planned breeding should take place. The queen will be obviously “different” during this time. She will be exaggeratedly affectionate, rubbing up against any people in her household. She will also become quite vocal.

Stage 3

Interestrus: The third stage of estrus lasts one to two weeks. During this stage, the queen will refuse to mate with the tom and will reject him aggressively if he attempts to breed her. If a female was not successfully bred during estrus, she may remain in interestrus for a week or two and then start a new cycle. If she was bred, which induced ovulation but she didn’t conceive, she may have a pseudopregnancy (false pregnancy), which can last for about two months and can fool even the most experienced of breeders.

Stage 4

Anestrus: The fourth stage of the estrus cycle is basically a time when the female’s reproductive system gets to rest. Her owners get to rest a bit, too.

Female cats are seasonally polyestrous. This means that they will have repeated heat cycles, during which they can become pregnant, throughout the course of a season or seasons, unless they are bred and become pregnant. These cycles are influenced by daylight, environmental temperatures and the presence of other cats. When there are at least 12 hours of daylight, and other conditions are optimal, the queen’s hormones are triggered and she goes into her heat cycle. Most cats in North America breed between March and September. Cats in the Southern hemisphere cycle from October to March.

Special Notes

The number of days that a female feline is “in heat” varies quite a bit. This is the phase of the reproductive cycle when the queen is receptive to the tom cat. If the queen is not bred when she is physically receptive to the male, her heat phase may last as little as 2 days. However, it may last as long as 19 days. In the early Spring, some females never completely come out of heat. Instead, their hormone levels and the associated signs of heat just wax and wane. Female cats are induced ovulators. This means that the physical act of mating causes them to ovulate. After a few breedings, their heat cycles will shorten in length, as eggs are released from the ovaries in response to a hormone surge triggered by being bred. Four breedings will induce ovulation in most queens. One breeding will produce ovulation in about fifty percent of intact female cats. Ovulation occurs 24 to 72 hours after the mating “event.” Signs of heat may be minimal, or in some females so pronounced that an owner may think that their kitty is ill. Typically, a queen in heat will cry, roll over, and in response to petting along her spine drop her forequarters and elevate her rear with the tail raised and held to the side. She may also be very interested in going outdoors (especially if a tom cat comes calling), and may show increased affection for her human companions.

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