When our beloved pooches are born, they appear in litters and often look similar to one another.
While this leads us to believe that the chances of them being identical twins is relatively high, the reality is anything but that.
Experts have stated that pups sharing a placenta can lead to fewer nutrients for each animal – meaning that it is rarer than some of us believe.
The Mirror spoke with canine behaviorist Adem Fehmi, who works with natural dog food brand Barking Heads, to get his thoughts on identical puppies.
He described the chances of identical twins in dogs to be “incredibly rare”.
Also explained the difference between fraternal twins and identical twins.
Fraternal twins are “born of the same mother but developed from an individual egg each, fertilized by a single sperm each” – so technically, all puppies in a litter are considered fraternal.
Genetically identical twins “must have developed from one egg that has split and become two embryos” – just like humans.
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Adem expanded: “These two embryos sometimes share the same placenta until they are born (although not always) and the one egg they have developed from would have been fertilized by one sperm.
“It is possible, but again thought to be incredibly rare, for two puppies born with other littermates to be genetically identical within the litter as a result of an egg splitting and two embryos forming.”
To establish whether two dogs are identical twins or simply fraternal twins, the breeder of the puppies would have to either witness the puppies attached to the same placenta at birth, or witness the puppies emerging from the same sack.
Adem said: “Alternatively, genetic testing would need to be completed, which is not readily available to most breeders and I would imagine, of no real benefit or interest to most.”
For these combined reasons, it is possible that many cases go undocumented.
Historically, there have been little recordings of identical twins in dogs.
In 2016, the world’s first ever identical twin dogs were genetically verified in South Africa.
A female Irish Wolfhound gave birth to brothers, named Cullen and Romulus, born in the same sack with attached umbilical cords.
Blood samples confirmed the twins were identical, and had arisen from the splitting of a single fertilized egg.
Researchers published their findings in the Reproduction in Domestic Animals journal.