Can Dogs Get Pregnant by Multiple Fathers?

When a female is in heat, she will emit signals that notify nearby males of her receptiveness to mating. These signals include yowling, presenting her rear and, most importantly for dogs, emitting pheromones. Any sexually intact male in the area is likely to respond and want to mate. While the males can fight, often very aggressively, once one male has copulated, it is possible for another to do the same.

Mating between dogs means the male and female share their genetic information. The resulting puppies will have characteristics of both, although these will depend on dominant versus recessive genes. Common shared traits are the morphology of their body and the color of their coat, but it can also affect behaviors and potential for various health problems.

Once they reach sexual maturity, female dogs have an average of two heat periods throughout the year. These usually coincide with the beginning of spring and the beginning of fall. The heat period is the common name for their estrus cycle, a cycle of four stages which are categorized under two main phases:

Follicular phase

This phase is characterized by the progressive development of ovarian follicles, which will give rise to eggs. These are the cells that receive the sperm to form the zygote and the eventual puppy fetus. The eggs travel until they reach the uterus where they implant and allow for fetal development (i.e. the dog's pregnancy). This phase has two stages:

• Proestrus: lasting 8 to 11 days, this stage begins at the moment vaginal bleeding appears until the dog accepts mating. During this period, ovarian follicles begin to develop and the dog attracts males while urinating more frequently.
• Estrus: this is the evident heat period during which time she is fertile. It lasts 5 to 10 days, during which the female accepts the male and can become pregnant with one or more dogs.

Luteal phase

This stage is characterized by the dominance of progesterone, a hormone produced by the corpus luteum. This occurs regardless of whether the female becomes pregnant or not. If the female becomes pregnant, progesterone is produced in the placenta. In turn, this phase can be divided into two stages:

• Diestrus: lasting 2 to 3 months, vaginal secretions disappear and the vulva returns to its normal state after becoming engorged during estrus. At this stage, the dog rejects the male, so she could not get pregnant from any dog.
• Anestrus: this stage is characterized because dogs have a hormonal rest of 4 to 5 months in which they do not have cycles.

Once the dog has ovulated, the eggs remain available for 48-72 hours to be fertilized by sperm. If the female mates during that time interval by one or two males or the mating has occurred up to two or three days before ovulation, there is a good chance that she will become pregnant by one or both males. Although rare, it is even possible for the dog to become pregnant by more than two fathers.

For those of us who have adopted a female dog, neutering in the form of spaying is recommended to prevent unwanted pregnancies. There is already a great strain on services to protect dogs, leading to many being destroyed in so-called kill shelters. Reducing the population allows us to better provide the right care for dogs overall, as well as reduce the strain of responsibility for us as guardians.

Learn about other myths and misconceptions about canine pregnancy with our article on whether a dog can get pregnant during her first mating.

Yes, a dog can become pregnant by more than one dog. It is particularly common in street dogs since they do not have owners to protect them and prevent mating. They are also less likely to be sterilized.

Although the same dog can have a litter from different fathers, this does not affect the gestation time of the pregnancy. The female will be pregnant for 58 to 68 days, although around 63 days is the average. Mating with more than one male can increase the litter size, but this is not the only determining factor. Genetics, health and other factors will influence litter size.

The difference in the same litter having different fathers will be in the appearance of the dogs. The genetic information will be split between the mother and multiple fathers, influencing traits such as appearance, especially if the males are of different breeds.

A dog can become pregnant by several dogs if she is mated by different dogs during heat. This can occur during the seven days before ovulation because the dog's sperm can remain viable in the female until that time. A lot of sperm can enter the female as the dogs get stuck together when mating. Otherwise, it will occur 48 to 72 hours after ovulation. This is the time in which the eggs are suitable or receptive to fertilization.

When a dog is crossed with several dogs during heat, there are sperm from different males in her reproductive tract. This means there is a good chance that different eggs will be fertilized by different dogs. The litter will be very genetically diverse, with the puppies generally presenting a very different phenotype from each other. They will necessarily look like siblings when the female is crossed with dogs of a different breed or physical appearance.

If a dog becomes pregnant and it threatens her health, multiple fathers in the same litter can exacerbate this threat. You can find out about what might be done in our article on terminating a dog pregnancy.

We have seen that a dog can get pregnant from several male dogs. A medium-sized female can have between three and five puppies, while large breeds can have between seven and nine puppies. Depending on the size, it may appear that the dog will be able to become pregnant with a greater number of dogs, since there are a greater number of eggs available to be fertilized by sperm from different males.

The number of dogs a female dog can get pregnant will depend mainly on her size and the number of eggs she releases during the given heat cycle. Even if a large dog is crossed with several males, she can become pregnant from all of them, but this is unlikely. Chance has a lot to do with it when a dog is crossed with so many different dogs. If a dog is crossed with two or even three dogs, they will all likely result in pregnancy. When she mates with more than three males, it is not common for her to become pregnant by each of them.

So far, we have spoken about the benefits of neutering a female dog to help avoid unwanted pregnancies. However, there is also a responsibility for guardians of male dogs. Learn more with our article which explains the benefits of neutering a male dog.

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