As anyone involved in cat rescue knows, domestic cats (as a species) are prolific breeders. In their natural habitat, cats survive 6-8 years and there is a high mortality rate among kittens. Cats have now spread around the world and it is essential that cat owners curtail the breeding abilities of pet cats to avoid overpopulation and cut the huge euthanasia rates among healthy pet cats. In the past it was common practice to destroy all but one of a domestic cat's kittens. In the early days of pedigree cat breeding, most pedigree females were allowed to raise only 2 kittens at a time; additional kittens were fostered by a non-pedigree queen whose own litter would be destroyed.

As individuals, some queens (the term for an unspayed female cat) can have litters so large that they cannot feed them all. Litter sizes vary between 1 and 9 kittens, with the average being 3 - 5 kittens. Some breeds are considered more prolific than others, both in terms of litter size, litter frequency and in starting to breed at an early age. Siamese cats are often said to be "over-sexed" in this respect (the table below seems to bear this out).

Because cats have only 8 teats, feeding such large litters is a problem and the weaker kittens are often pushed aside by stronger kittens and therefore die unless the owner helps to rear them or a foster mother is found. A cat called Percy, reared her 12 surviving kittens by dividing the litter into two halves and placing each half-litter in separate nests in opposite corners of the nursery room. There were thus 2 "sittings" for meals. Provided the mother cat is well nourished, it is possible for her to raise a large litter. Kittens from a large litter are small compared to kittens from an average litter. There simply isn't enough room in the mother's womb for them to reach a normal birth-weight. Provided they survive the crucial first few days and are well fed, they usually make up for this in the first few weeks.

A female cat reaches sexual maturity at around 6 months, though this varies according to breed and seasonal condition. Siamese and Oriental cats are renowned for being precocious and reaching sexual maturity at 5 months old while Persians tend to mature later at 7 months (sometimes not until 11 months). Because cats are genetically programmed to breed in spring and summer when prey is more abundant, a queen who is 6 months old in mid-winter might delay her sexual maturity until spring, 3 months later. Sexual maturity is characterised by the queen calling for a mate, rubbing against things and lying on her belly with her rump in the air and her tail cocked to one side (the mating position) in the hope that a tomcat will turn up and mate with her. She continues to call for several days and if not mated, she temporarily stops calling - only to start all over again 2 weeks later! Some cats, particularly Siamese and Orientals, call almost continuously with hardly a break.

Sexual maturity occurs earlier than physical maturity, hence most breeders don't let their queens breed at 6 months, but prefer to wait until she is older and more physically mature. Queens are "induced ovulators" i.e. they ovulate after mating to ensure the best chance of fertilization. During their oestrus (period of calling) they will mate with several tomcats if given the chance. This means that a single litter may contain kittens sired by different males. It also guards against mating with an infertile tomcat (a "dud") and not conceiving. In addition, the tomcats who mated with her during her oestrus are less likely to harm her kittens, believing them to be their own offspring (though not a hard and fast rule, tomcats that did not mate with her might kill her kittens to make the female start calling again and give the new tomcat a chance to mate with her - wiping out his competitors' offspring in the hope of siring his own).

Queens are most fertile between 2 and 8 years old and their fertility also depends on their state of health and nutrition. Though an unspayed female will continue to breed beyond that age, their litter sizes and numbers of litters decrease. Usually, queens produce 2 or 3 litters per year and only call for mates during the warmer months when kittens are more likely to survive. During the winter months, when days are shorter, the weather is colder and prey is more scarce, most queens cease 'calling' for mates. Central heating, artificial lighting, good nutrition and more protected lifestyles means some queen can produce 4 or 5 litters per year, breeding right through the winter. Though not a problem for breeders of pedigree cats, this is a serious problem in warm climates with abundant prey and now natural predators, such as Australia, where year-round breeding is normal.

Bearing in mind that many cats have their litters out of human sight and that not all kittens survive, the two most prolific breeders whose achievements have been verified are listed below. Given the dates of their achievements, many of the kittens would have died relatively young from disease. A queen whose whole litter dies (or is destroyed by the owner) will quickly come back on oestrus, mate and have another litter. There are many more whose claims of prolificacy cannot be verified. In the interests of preventing feline overpopulation, large numbers of strays and high shelter euthanasia rates, Messybeast.com is not in favour of allowing cats to produce so many kittens.

The collective noun for kittens (other than a "litter" of course!) is a "kindle". The act of giving birth to kittens is also known as kindling (verb "to kindle") and is used for both cats and rabbits. Bitches "whelp" and queens "kindle"!