Did you know that a litter of kittens can sometimes have more than one father? If you ever looked at a bunch of adorable kittens and wondered how they could possibly be related, you might have witnessed a phenomenon known as superfecundation.
First, what is superfecundation?
“Superfecundation occurs when a female mates with two or more males,” says Donald Shellenberger, DVM, of VCA Smoketown Animal Hospital in Lancaster, Pennsylvania. “One litter can potentially have multiple fathers as long as they all mate with the female in the optimum time of conception.”
Potentially, a litter of kittens could have two or even more fathers. This situation is often seen in stray animals, as well as in un-spayed female cats who live in the same household with one or more intact male cats. (A single kitten cannot have multiple fathers; each individual kitten in a litter has only one father.)
“It’s probably more common in dogs than cats since cats ovulate with copulation,” Dr. Shellenberger says. “It can happen with other species, especially in animals with multiple eggs and large litter sizes.”
How does superfecundation happen?
For cats, the optimal window for conception is shorter than it is in dogs. A cat’s fertile period can theoretically be up to seven days but is sometimes as short as one day. (To compare, dogs are fertile for about two to three weeks.) Cats are induced ovulators, which means that the act of mating signals the ovaries to release eggs. So, if a female cat copulates with more than one male cat during the fertile period, her eggs can potentially be fertilized by more than one male.
How can you tell if a litter of kittens has more than one father?
“You can tell if kittens in the same litter have different fathers by the [kittens’] characteristics, sizes and colors,” Dr. Shellenberger explains.
It can be easier to figure this out with puppies since body size and other physical characteristics can vary so wildly. For instance, if a litter of puppies contains some pups who look like Chihuahuas and some pups who look like Basset Hounds, superfecundation might be the culprit.
In cats, however, physical characteristics have much less variation (for instance, there are no 80-pound cats — at least not domesticated cats!). Certain coat colors and eye colors can be recessive, so those aren’t always clear-cut signs. The main tip-off is kittens who look drastically different from each other. When the parents are of mixed ancestry (domestic shorthairs or orange tabby cats), it can be harder to know, especially if you don’t know the predominant breeds in each cat’s mix. But if the mom cat is a Ragdoll and you see several kittens who look like domestic shorthairs and some who look like Persians, you might have a case of superfecundation on your hands.
If the mom and all the potential fathers are purebreds of the same breed, it can be impossible to know if more than one male sired the kittens. In suspected cases like this, a DNA test can get to the bottom of each kitten’s parentage.
How often does superfecundation in cats happen?
Superfecundation happens more often than you might think, and with cats, you might never know a litter has more than one father. “In animals that are free to roam as they please, it’s fairly common,” Dr. Shellenberger says.
Thumbnail: Photography ©skynesher | E+ / Getty Images.