Meet the first proven set of identical twin puppies

When an Irish Wolfhound became distressed during labor, her owner took her to a veterinarian for a C-section. This is a fairly normal practice, but Dr. Kurt de Cramer was in for a surprise. For the first time ever in his practice, he found two of the five puppies attached by an umbilical cord to the same placenta. Normally, each puppy has its own placenta, so seeing these two share one was cause for excitement. To make sure what he thought was happening was actually happening, de Cramer had a genetic analysis done. Lo and behold, he was right – these two puppies were identical twins!

This is the first documented case of identical twins in domestic dogs in history. While there have been reports of twins in dogs, there haven’t been any scientifically proven until now. It turns out that although human twins are relatively common, twins in other species are very rare. The puppies, named Cullen and Romulus, are certainly special.

Scientists speculate that twins are rare in other animals because two organisms living in a single placenta will have less nutrients overall than their single sibling counterparts. This means that they’ll be smaller, weaker and at a disadvantage when it comes to surviving in the wild. That said, the number of cases of identical twins in nature is likely different than we speculate because of the lack of documentation and minimal genetic testing. It is known, though, that at least one species of Armadillo regularly gives birth to identical quadruplets.

Still, Cullen and Romulus deserve recognition. It’s an exciting case for scientists and dog lovers alike. Perhaps even more interesting is that while they look similar, their appearance isn’t identical. They have varying white markings that prove an interesting point. Although they have the same set of genes, how these genes are expressed is still influenced by environmental cues. This is why human identical twins still have differences in appearance, as well.

These two pups are going to have a fun-filled life with special recognition since their birth. We hope that they can continue to help with our growing knowledge of the canine companions that we so deeply love and admire. For more information on the puppies and identical twins, visit National Geographic.

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