It’s been a pretty great week for dog research, but the most delightful piece of canine news to emerge in the past few days may be this: Scientists have just discovered the first known case of identical dog twins. You know what’s better than one puppy? Two puppies. Dog math.
As the BBC reported earlier this week, the twins, named Cullen and Romulus, were discovered in South Africa by veterinarian Kurt De Cramer, who delivered them via Cesarean section. Multiple births in dogs are par for the course — the average dog will give birth to five or six puppies in a single litter — but unlike the rest of their siblings, Cullen and Romulus shared a single placenta, a condition that typically means the animals won’t last long outside the womb.
“It is even less likely for placenta-sharing puppies to survive, because of several complications relating to nutrient and oxygen supply from a single placenta having to do the job that is normally done by two placentas,” De Cramer told the BBC. But survive they did, adding dogs to the small list of mammals that can birth identical twins — right now, the only other species are humans and nine-banded armadillos, which, per the BBC, “give birth to identical quadruplets, each with their own placenta.”
De Cramer and his colleagues, who tested the pups’ DNA after birth to confirm their identical status, described their finding in a paper published last week in the journal Reproduction in Domestic Animals. But just because Cullen and Romulus are the first documented case of identical twins doesn’t necessarily mean there haven’t been others: “There have been rumours about twins in dogs before,” co-author Carolynne Joone, a veterinary researcher at Australia’s James Cooke University, told the BBC. “We just happened to be lucky enough to be able to confirm it genetically.”
Lucky for the rest of us, too, that it led to photos like these: