Can Dogs Have Identical Twins? Here's What Science Says

Can Dogs Have Identical Twins? Here's What Science Says

Author WDF Staff

06.02.2022.


Dog owners love their dogs; that’s not a big secret. Sometimes, that love makes us wonder about our dog’s origin, life, family, and birth. One of the questions we heard was, “Can dogs have identical twins?” Naturally, we assumed dogs could easily have identical twins. After all, they are all born in the same litter, and when humans have two babies, they are considered twins, right? Shouldn’t that be the same for dogs? Well, the truth is a bit more complicated than that.

What exactly are identical twins?

The easiest way to define what twins are is - two offspring produced by the same pregnancy. Since that is always the case of the same litter in dogs, twins are pretty common. However, there are two types of twins, and they don’t necessarily have to be identical. Twins can be fraternal or identical.

Fraternal twins

Fraternal twins are developed from two different eggs. That means that each egg is fertilized by its own sperm cell.

border-collie brothers

Identical twins

Unlike fraternal twins, identical twins are developed from the same egg. The egg will split and form two embryos.

Are all dog litters twins?

Dogs have different numbers of eggs that can get fertilized. In humans, that number is usually one, sometimes two, and rarely more than two. In dogs, all litters are fraternal twins. Identical twins were nearly impossible to confirm. They are rare, but identical twins can happen in different animal species. Some of the species where identical twins occur are cows, pigs, and horses.

The only confirmed case of dog identical twins

Until 2016, identical twins in dogs were nearly unheard of. The main problem is that we couldn’t confirm two puppies were actually born as identical twins. In 2016, a South African Irish Wolfhound breeder had a planned litter that produced two identical twins. So far, this is the only confirmed case of identical twins in this species, but it is most likely that we simply don’t have the supporting data.

two dachshunds

The Irish Wolfhound brothers were born in the same sack, and they had attached umbilical cords. There were five other puppies in the same litter, and each one had its own placenta, which is something you’d expect from a dog litter. When the identical twin puppies turned 6 weeks, a team of geneticists took DNA samples from the puppies and tested them. They confirmed puppies were actually identical twins. The discovery was so important that the research was included in the journal “Reproduction in Domestic Animals.”

Are identical twins actually identical?

On a DNA level, identical twins share a lot of their genes. However, you can never be entirely sure how the genes from both parents will pair. That means there are subtle differences in some coat colors, habits, health, and other physical characteristics. However, identical twin puppies are nearly indistinguishable.

two pug brothers

Many human identical twins share habits, mannerisms, and many different things. However, they are rarely separated and brought up in different environments. The case with these puppies will be completely different. It will be interesting to see how they will develop in different homes.

In conclusion

Identical twins in dogs can happen, but they are very rare. There is simply not enough data, and only a tiny portion of domestic animals go through such DNA testing that might confirm they are identical twins. It is most likely they happen, but humans simply don’t know about it.

World Dog Finder team

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