One Litter, Two Sires

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Have you ever wondered if a litter might have more than one father when the kittens are born with a wide variety of colors?

Just because a litter has white and blue and black and red kittens, some tabbies and some with white spotting, and maybe a smoke and a calico, and even a pointed kitten, it does not necessarily mean that more than one sire was involved as long as the genes necessary to produce such a range of colors are possible in one sire, given the mother's color.

That said, it is also entirely possible for a litter of kittens to have more than one sire. To understand how this can happen, you first need to appreciate a bit about the uniqueness of the female feline reproduction system.

Induced Ovulation

In most mammals, the egg or eggs are released from the ovaries when a female comes into heat. The eggs are then ready for fertilization as soon as the female is mated.

That's not how it works in cats, however. Cats are "induced" ovulators. The eggs are not released when the cat comes into season. The female only releases her eggs in response to certain physical stimuli created by the male during the act of mating. Mating, or even "heavy petting" during a heat cycle produces a neurological signal in the female cat that in turn stimulates the release of a hormone that causes ovulation. All eggs that mature in that cycle are then released.

It is the act of mating that "induces" the female to release her eggs — and so the cat is called an "induced ovulator."

Rabbits, alpacas, llamas and camels are also induced ovulators.

A whole male cat has barbs on his penis, and upon withdrawal, the female cat will often scream (whether from either ecstasy or pain, we do not know). It is believed that the barbed penis may also stimulate ovulation.

The more times a cat is bred during her heat period, the better the chances that her hormone levels will be stimulated sufficiently to cause ovulation, although it should be noted that even a single mating can be enough to cause ovulation of many eggs.

Ovulation typically occurs within 20 to 50 hours after mating. The eggs are released into the oviducts where they are capable of being fertilized for about 24 hours after being released. After ovulation, and subsequent breedings by any number of male cats could supply the sperm that fertilizes some of the eggs. During this window of opportunity for fertilization, it is possible for different male cats to sire some of the resulting kittens.

The fertilized eggs make their way to the uterus via the uterine horn, implanting in the uterine lining within 10 to 12 days after fertilization.

If there is no mating in an induced ovulator, the heat period (estrus) may continue for many days, followed by 'interestrus ,' and the estrus phase starts again until mating and ovulation occur.

The female cat in heat has an estrus of 14–21 days. If bred without becoming pregnant, the female will continue to cycle about every three weeks.

Feral Cats

While cat breeders supervise the breeding of their female cats, ensuring only one male has access to a queen during her heat period, feral female cats on the street or in the wild usually mate with multiple tom cats when in heat — and the female may be calling in season for up to 21 days, with an average of seven days. Female cats are quite promiscuous. If given the chance, most will mate with multiple males when they are in heat. Although genetics of the female cat may come into play, litters of multi-colored kittens often vividly demonstrate more than one sire.

Female ferrets must be impregnated once they enter the heat cycle,
or else they will die from prolonged exposure to hormones.

The Pedigreed Cat Breeder

The cat breeder plans out each breeding, then puts the selected male and female together, typically over a 3 day period when the female is in season. Of course, there are occasions when everything may not go as planned. A female may "escape" her honeymoon suite and mate with another male. Or a 5 month old male kitten may have matured faster than expected and mated with a female without his owner's "permission."

There have even been times when an owner was unaware of a second male having bred a female - until the litter was born and it contained unexpected colors that were impossible if sired by the selected mate.

What To Do If You Suspect Multiple Sires

If there is a possibility of two sires in a pedigreed litter, or if there is a doubt as to who the sire might be, DNA testing is now available. Samples from each kitten, the mother, and possible sire candidates can be submitted to a testing lab to determine the parentage.

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