Cats in the same litter can have different colors, patterns, sizes, and even breeds. The only explanation is that the kittens have different fathers.
Cat litters can have more than one father due to superfecundation. Female cats’ egg production is induced by mating. When the female produces multiple eggs, and mates multiple times, the eggs can be fertilized by different fathers. The kittens are born in the same litter.
What makes this possible is the cat’s unusual way of reproducing. And what makes the process even more fascinating is that the litter can actually have more than two fathers.
Can Cat Littermates Have Different Fathers?
If the kittens in your cat’s litter look like different breeds, you may wonder whether they have different fathers. While this sounds unlikely, it is possible, through a biological phenomenon known as ‘superfecundation’.
To grasp how this happens, you have to understand the cat’s reproductive process. How can a female cat have a litter with different fathers?
What is Superfecundation?
‘Superfecundation’ means two or more eggs being fertilized in the same heat cycle. This can occur when the same pair mate multiple times during the cat’s heat cycle. But it is also possible for different fathers to fertilize each egg, which is known as ‘heteropaternal superfecundation’.
The term ‘superfecundation’ comes from Latin. ‘Super’ means above or beyond. ‘Fecund’ means fertile, which means that ‘fecundation’ means fertilization. So, the term means ‘after the first fertilization’.
This is essentially what happens. The female will produce several eggs, some of which are fertilized by the partner it is currently mating with. It can then mate with another partner soon after to fertilize the rest of the eggs. They are quite literally fertilized ‘after the first fertilization’.
This is advantageous from an evolutionary perspective. If its offspring with one parent is unviable, then the offspring from the other parent won’t be affected by the same genetic issue.
Superfecundation in Cats
To fully understand how superfecundation works, you have to first understand how cats mate. You will already be familiar with some of the process, but perhaps not all of it.
Cats can’t have kittens any time that they like. They are ‘seasonally polyestrous’, which means that they come into heat. This is a period of time when the cat can ovulate, i.e. produce eggs that can then be fertilized.
Crucially, the way a cat produces an egg is different from other animals. Cats only release eggs from their ovaries when they mate. The term for this is ‘induced ovulation’, and it makes the mating process more likely to be successful.
Other animals produce eggs on a regular cycle. Reproducing in this way isn’t as effective, because mating outside of this cycle means that there is no egg to fertilize.
Repeated Mating and Superfecundation
Once the eggs are released, and the cat mates, some of the eggs are fertilized. Once an egg is fertilized, it travels from the fallopian tubes (which connect the ovaries to the rest of the reproductive system) to the uterus.
Normally, an egg will disintegrate within 24 hours or so if it isn’t fertilized. And once a mammal has a fertilized egg, its body stops producing further eggs. That’s why female mammals don’t have periods when pregnant, because they stop producing eggs from their ovaries.
Getting pregnant again halfway through pregnancy would interfere with the development of all the offspring. So, the body doesn’t allow it to happen.
But the cat doesn’t stop being in heat once it mates. It can mate again within that 24-hour time frame, either with another tomcat or the same one. If the female released multiple eggs, and one of them isn’t fertilized yet, then it may be fertilized by the second father. That’s how heteropaternal superfecundation occurs.
This can occur with more than two fathers. Theoretically, there’s no limit to the number of fathers who could have been involved in siring a litter. Cats are promiscuous, and can mate several times in a short amount of time.
Can Cats Be Pregnant with Two Different Litters?
To be clear, the eggs aren’t somehow stored separately, one kept aside for later. Once an egg is fertilized, it heads to the uterus (the womb). Here, it attaches itself to the womb lining and begins to develop.
If another egg is fertilized soon afterwards, it will do the exact same. It will head from the ovaries to the uterus, where it will implant itself in the uterine lining. It will then begin developing too.
What this means is that the cat then has two litters developing in its uterus at the same time. This doesn’t necessarily mean that the overall litter will be twice as large. But, genetically speaking, they are two different litters.
These litters will develop at roughly the same pace. They will be birthed at the same time. So, in a sense, they are two litters within one litter.
Why Do Cats from the Same Litter Look Completely Different?
Superfecundation can lead to kittens looking different from their brothers and sisters. In some cases, these differences are slight, as they are in normal litters. But you may notice big differences like different breeds, or long hair vs. short hair.
However, kittens in the same litter can look different even if they have the same father. Even though they are born at the same time, kittens are only fraternal twins. This means that they have the same amount of shared genetics as regular siblings.
There’s still room for them to look different. Regular littermates can be different colors, different sizes, and have different personalities. So, the fact that they look different isn’t proof enough of superfecundation.
Can Kittens Have More than One Father?
Despite superfecundation being real, that doesn’t mean that a kitten can have more than one father. It is possible for an animal to have three parents. This has been done artificially in a lab, but is not observed in nature.
Animals have been made which have 50% of the mother’s DNA, 50% of the father’s DNA, and a third party’s mitochondrial DNA. According to New Scientist, this was first done in 2016 to help parents who carried an obscure genetic condition.
But outside of science, the way that genes work dictates that only two animals can be a parent to one animal. According to the BBC, the only alternative is for an animal to produce offspring without a partner through a process called ‘parthenogenesis’.
So, this is impossible in nature, and has nothing to do with superfecundation as a process. What is possible is for littermates to have different fathers. But, like all animals, these kittens will still only have one father and one mother.
How Common is Superfecundation?
Superfecundation is extremely common in cats.
According to the Royal Society, the percentage of litters with more than one father is up to 83%.
This can easily be proven by comparing the DNA of littermates to see whether they are full siblings or half-siblings.
However, the story isn’t entirely clear. According to the study above, the percentage may vary depending on where you live. A litter of a cat in the city is more likely to have more than one father (70-83%) because there are far more tomcats available for mating.
In the country, though, there are fewer cats around. As such, the proportion of litters with more than one father may be as low as 0-22%.
But whether this phenomenon is common or not isn’t an issue. Superfecundation doesn’t result in any birthing issues, for example. It doesn’t increase the likelihood of any of the kittens dying. It doesn’t have any functional effect on the litter once it’s born.
Does Superfecundation Occur in House Cats?
Superfecundation can occur in both house cats and feral cats. All that is required is for the mother to mate with more than one tom cat.
However, whether it’s likely to happen in your cat depends on how you care for it. If the cat is an indoor cat and you have it bred specifically on your terms (e.g. with a local stud cat), then it can’t happen. But if your cat is an outdoor cat, you can’t control which other cats it mates with.
The phenomenon is much more likely in feral cats. These cats are often not spayed, so they can mate and produce offspring. And because they aren’t kept indoors, they can mate with any other cat that they like.
Signs of Superfecundation in Cats
The most effective way to tell whether kittens have the same mother and father is genetic testing. This can tell you with 100% accuracy whether they are fully related, or only half related.
But there are several tell-tale signs which indicate that half the litter may have a different father. These big differences are easy to spot. You may have already noticed them, which is what led you to this guide.
1/ Different Breeds
Some of the cats may have a completely different appearance, plus several markers for a separate breed. This would indicate that the litter has two different fathers.
Cats of different breeds can breed with each other without a problem. They aren’t a different species, in the same way that two people who look different aren’t a different species.
What you might notice depends on the breed of your cat. If your cat is a pure breed, then what you may see is that half the litter is pure breed while half are moggies. Or if your cat is a moggie, then half will be moggie, while half will have certain characteristics of a pure breed.
So, for example, it might have the snub nose of a Persian. Or, it might have a triangular head and slender body like a Siamese. These features won’t be as strong as in a full Persian or Siamese cat, but they will be present.
2/ Different Colors
Cats of all kinds, purebred or not, come in many different colors and patterns. Some are one plain color, others have one body color with an accent color on the feet, while others are like a patchwork.
If half of the litter is one color and the other half are another color, they may have different fathers. One father could have been one color, and the other father another color.
This isn’t a sure sign, because the color is variable in cats. Even full siblings may have different colors and patterns. But if there is a clear divide with half of the cats one color, and the other half another completely different color, different fathers may be the cause.
3/ Long Hair and Short Hair
Another difference you may notice is in the length of your cat’s hair. Say, for example, that you have a Persian cat with long fluffy hair.
If it has a litter from two different fathers, then some may be purebred Persian, while others will be moggies. The Persians will have longer hair than the moggies. The quality of the fur may also be different, i.e. it could be thicker or more lustrous in some of the kittens than in others.
This is a feature you don’t see much variation in. Cats can have lots of recessive genes that change the colors and patterns in their fur. But you won’t see a regular moggie develop fur as long as a Maine Coon in one generation of breeding.
4/ Different Sizes
You may also notice that some of the cats are much larger than the others. The difference may be in weight, but could also relate to the different length of limbs, of the tail, of height, or some other aspect of size.
Some variety in size is to be expected in cat litters. But if some of the cats are significantly bigger than the others, then they may have a different father. This can be an issue, because larger kittens will hog all the food for themselves. This may lead some kittens to not thrive as well as they might.
5/ Different Ages
One kitten in a litter may be older than another because of this phenomenon. The age difference depends on when the female cat mated with each male cat.
However, the age difference is minimal. A cat’s gestation period lasts 65 days. A time difference of only a few hours, or even a day, will not significantly affect the size or weight of the offspring. They may be slightly smaller, but not enough to have an effect.
Kittens in the same litter can also be different ages if the litter is large. The female may take a lot of time birthing all the kittens, whether because of birthing issues, or because there are a lot of them.
The vet may also recommend stopping the birthing process halfway through to allow the cat some rest. This can result in some of the kittens being a day older than the others.